ETS Harvest Guide 2026

H A RV E S T GUIDE 2026

ETS LABORATORIES

TA B L E O F C O N T E N T S page 19 Non-Saccharomyces Yeasts Diagnostics

pages 01-06 Harvest Toolkit This short guide will give you the highlights of our most requested Harvest testing.

pages 21-25

The PCR-based diagnostics can be used to determine implant success with commercial strains of nonSaccharomyces yeasts.

Analysis of Grapevine Red Blotch Our molecular testing provides quantitative results to support vineyard management and planting decisions.

pages 08-17 ETS Juice Panel Get the complete picture for informed winemaking with the harvest Juice Panel and insights from the 2023 - 2025 Harvests.

page 07 Maturity Monitoring The ETS Grape Maturity Monitoring Panels provide sets of analyses requested to monitor fruit maturity.

page 18 Scorpions Find out what microbes are coming in on your grapes using Scorpion diagnostics.

page 26 Volatile Acidity

page 20 Yeast Viability by Flow Cytometry The concentrations of total and viable yeast are important indicators of fermentation health.

Recognize the microbes and conditions that lead to VA formation to develop an effective monitoring and prevention program.

pages 29 - 30

page 27

Phenolics Program

pages 37 - 38

ETS offers a full suite of advanced HPLCbased analytical tools to evaluate phenolic compounds in grapes and wines.

Aromas

pages 47 - 48

Detect and prevent common (and uncommon) sensory flaws.

Sampling and Shipping Get the most out of your results by using these sampling guidelines.

Potential Alcohol Get a closer look at using glucose+fructose analysis to estimate potential alcohol.

page 28 Sugar Analysis Sugar can mean a number of things.

See what’s behind your “Residual Sugar” numbers.

pages 39 - 46 pages 31 - 36 Phenolic Maturity The ETS Red Grape Phenolic Panel

The Impact of Wildfires The Extended Volatile (“free”) and Glycosylated (“bound”) marker panels, currently offered by ETS Laboratories.

And your most-asked questions, answered.

pages 49-54 Our Locations pg. 50- St. Helena pg. 51- Healdsburg pg. 52- Paso Robles pg. 53- Newberg pg. 54- Walla Walla

HARVEST TOOLKIT As wineries enter the 2026 harvest, timely analytical information remains one of the most valuable tools for making informed decisions, from fruit maturity through primary and secondary fermentations.

This guide brings together the analytical tests, data, and technical resources most relevant during harvest. Whether used for planning, resource allocation, or as a quick reference during the busiest weeks of the season, it is intended to help production teams respond confidently as conditions evolve.

ETS Laboratories has worked alongside wineries through changing vintages and an ever-evolving wine industry, utilizing cutting-edge technologies since opening our doors in 1978. Today, we continue to provide reliable laboratory data, practical technical support, and responsive service to help drive our clients’ success.

The ETS team looks forward to supporting you throughout the 2026 harvest season.

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G R A P E M ATU RI TY M O N I TORI N G PAN ELS The ETS Grape Maturity Monitoring Panels provide a set of analyses that growers and winemakers request to monitor fruit maturity, including °Brix, glucose and fructose, TA, pH and malic acid, as well as berry size parameters and average sugar per berry. Monitoring sugar per berry allows growers to determine the duration and rate of active sugar loading, during which vines synthesize and actively transport sugar into berries. The time at which the sugar loading phase ends, and what level of °Brix was achieved at that time, are both important indicators of wine growing conditions (excessive or insufficient vigor, water availability and resistance to heat stress).

For more details see pg. 7

E T S S CORP I ON S TM Wild yeast and bacteria from the vineyard may be introduced into the winery on the harvested fruit, causing spontaneous fermentation and/or spoilage. ScorpionsTM DNA analysis offers winemakers an early detection tool to identify these spoilage organisms.

Despite best practices of modern winemaking methods, microbial contamination often occurs during wine production.

Spoilage microbes are capable of survival and growth in wine, potentially producing off-flavors, off-aromas, and turbidity.

Microbiological contamination is often undetected until related problems in the wine become noticeable by sensory evaluation.

Scorpions™ assays, based on specific genetic targets, detect the full range of wine and juice spoilage organisms. This genetic analysis method detects microbial populations directly in wine or juice. Results are routinely reported within two business days, giving winemakers the ability to address problems before wine defects occur.

Targeted genetic probes give the winemaker the ability to monitor the specific spoilage organisms that have the potential to adversely impact wine quality, and to accurately measure populations down to extremely low levels.

For more details see pg. 18

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H A R V E S T TOOLKIT

GR A P E WAT E R CONT E NT Changes in grape water content influence finished wine composition and can be as important as standard sugar and acid measurements when making picking decisions.

Grape water content is also very useful for understanding changes in TA, pH, ºBrix, and other harvest indicators.

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G R AP E P HEN OLI CS

HARV ES T JU I CE PANEL

To monitor ripeness, follow changes in grape phenolics, using the catechin and tannin “ripeness” index .

With quercetin analysis, monitor canopy effects on grape phenolics.

Our most popular harvest panel offers a full range of grape and must analyses, combining more than ten tests.

These include fermentable sugar,to help estimate alcohol content, and Yeast Assimilable Nitrogen (YAN), to help predict sluggish or stuck fermentation and potential sulfide formation.

For more details see pg. 29

For more details see pg. 8

H A R V E S T TOOLKIT

EUC A LYP TO L

B OTRY TI S PAN EL

Eucalyptus character is a controversial sensory expression in red wines from California and countries with Mediterranean climates.

Even a slight “eucalyptus” note can interfere with delicate varietal aromas, and can have a detrimental influence on certain grape varieties.

This comprehensive test panel evaluates grapes for Botrytis (using Scorpions™) and laccase, detecting both the spoilage organism and its byproducts that can harm your wine.

For more details see pg. 37

GRAP EV I N E RED BLOTCH Grapevine red blotch disease (GRBD) is a major vineyard viral disease impacting the wine industry. Our molecular testing provides quantitative results to support vineyard management and planting decisions.

For more details see pg. 21

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H A R V E S T TOOLKIT

5

GLUTAT H IO N E

WI L DFI RE I M PACT

M ON I TORI N G IBMP

Glutathione, a natural grape antioxidant, can protect the aroma and flavor of white and rosé wines and prevent premature aging. Glutathione levels can fluctuate during production, depending on oxygen pickup and yeast absorption/release during the fermentation process.

Wildfire smoke contains compounds that can penetrate grapevine tissues and ultimately result in unwanted flavors in wine. Analyzing for these compounds allows winemakers to evaluate the potential effects of wildfire smoke and make informed decisions to help mitigate its impact.

IBMP is the compound responsible for the characteristic green bell pepper aroma in wine.

Its concentration decreases as grapes mature, making harvest timing critical. Monitoring IBMP levels during ripening helps growers and winemakers optimize picking decisions and influence the final sensory profile of the wine

For more details see pg. 38

For more details see pg. 39

For more details see pg. 38

H A R V E S T TOOLKIT

YEA ST V IA B I L I T Y

R A PI D P HEN OLI CS

DN A FI N GERP RINTING

Our automated method provides yeast viability and total cell count results within hours. Using realtime microscopic flow image analysis, the system evaluates up to 1,000 times more sample volume than standard microscopic methods, improving the accuracy and reliability of every analysis.

Mon itor i ng phenol ics throughout maceration and fermentation, provides the insight needed to make informed extraction decisions, helping winemakers achieve their desired tannin structure, balance and style. The tannin content of a wine is already fixed. Monitoring phenolics during this critical period allows winemakers to better control tannins by increasing or decreasing phenolic extraction.

ETS Laboratories offers DNA fingerprinting to distinguish between closely related strains of Saccharomyces cerevisiae.

ETS MLVA technology provides winemakers with a powerful tool to track yeast populations during native fermentations and evaluate the effectiveness of commercial inoculations.

For more details see pg. 30

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MONITORING

MATURITY

ETS GRAPE MATURITY MONITORING PANEL W H AT I S T H E E T S G R A P E M ATU RI TY M ON I TORI N G PAN EL? The ETS Grape Maturity Monitoring Panel combines key analyses used to assess fruit maturity and monitor ripening throughout the growing season.

This panel combines the traditional measurements of juice solids (°Brix) and acidity (titratable acidity and pH), with a more accurate determination of fermentable sugars (glucose and fructose). It also includes malic acid analysis, a well-established indicator of fruit ripening that provides additional insight into grape maturity and supports informed harvest decisions.

In addition, the panel reports berry size parameters (volume and weight), and sugar per berry, a calculated value based on the average berry volume measured by the Dyostem system. Berry size uniformity is assessed through the coefficient of variation and a histogram illustrating the distribution of berry volumes, providing a more complete picture of fruit maturity and vineyard uniformity.

W H Y M O N I TO R S U G A R P ER B ERRY ?

Monitoring sugar per berry allows growers to determine the duration and rate of sugar loading. Post veraison, vines synthesize and actively transport sugar into berries.

At the end of this phase, °Brix usually keeps increasing due to berry dehydration.

Monitoring °Brix cannot determine when the sugar loading phase stops. When sugar loading stops, the actual quantity of sugar accumulated in each berry remains unchanged (see Fig 1).

The duration of the sugar loading phase and the °Brix achieved at that time, are all important indicators of vine growth conditions. Excessive or insufficient vigor, water availability, and resistance to heat stress all have an impact. Vines under moderate hydric stress typically reach between 21 and 23 °Brix at the end of sugar loading.

Vines with excessive vigor typically see their sugar loading stop before these levels are reached, as vegetative growth may compete with sugar synthesis and accumulation.

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These vines often tend to “shut down” more easily in response to heat waves, which can prompt a sudden end of sugar accumulation in berries. Vines that have nutrient deficiencies, are under significant stress, or are diseased also have difficulty reaching typical °Brix levels. At the end of sugar loading, a variety of maturity events are triggered that influence the development of grape aroma compounds and phenolics.

This is often used as an indication of when to start grape phenolics measurements (see Vineyard Decisions – Grape Phenolic Panel pg. 29)

ETS

JUICE PANEL 2025 HARVEST DATA

J

uice chemistry analysis provides winemakers with a comprehensive understanding of muscomposition at harvest, extending beyond traditional measurements such as tartaric acid, pH, and °Brix. This broader view is important because the composition of grape juice can vary significantly from one vintage to the next.

Together, these advanced analytical tools provide insight needed to make informed vineyard management decisions, optimize harvest timing, guide fermentation, and influence wine composition.

Juice chemistry is the foundation for the resulting wine. Producing wines with specific targets for ethanol and acid balance, while avoiding fermentation-related problems, requires a thorough understanding of the juice chemistry. Understanding these changes allows winemakers to achieve their desired wine style.

The 2025 vintage was relatively cool compared to the 2024 vintage, and similar to the 2023 vintage as shown in the following chart.

GROWING DEGREE DAYS

8

As is common in cooler vintages, sugar accumulation progressed more slowly in 2025. Although Chardonnay °Brix in early August was comparatively higher than in 2023 and 2024, the rate of accumulation was relatively flat. By November, it was more than 2 °Brix lower than 2024 and 1.5 °Brix lower than 2023. °B RI X

CHA RDONNAY MULTI VINTAGE

Likewise, Cabernet Sauvignon °Brix was slightly higher in mid-August of 2025 as compared to 2024 and 2023. Sugar accumulation was very slow and, by mid-November, was 4 °Brix lower than the 2024 vintage and a little more than 1 °Brix lower than the 2023 vintage. °B RI X

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CAB ER NET SAUVIGNON MULTI VINTAGE

Interestingly, the observed ratio of fermentable sugar to °Brix was reduced in the 2025 vintage in both Chardonnay and Cabernet Sauvignon. A reduction in 0.3-0.6 g/L glu/fru/°Brix can result in a 7 - 14 g/L reduction in fermentable sugar. Potential ethanol based on °Brix values could be lower by as much as 0.4-0.8% for the 2025 vintage.

GLU/ F RU: °B RI X

GLU/ F RU: °B RI X

C HA RDONNAY MULTI VINTAGE

C A BERNET SAUVIGNON MULTI VINTAGE

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N I TRO G E N COMP OUND S As with other juice chemistry components, yeast assimilated nitrogen (YAN) values can fluctuate vintage to vintage due to changes in ammonia and/or nitrogen by OPA (NOPA). Monitoring during harvest enables comparison with past vintages. There can be large differences in the amount of YAN in different varietals and in different geographical regions. Ammonia and NOPA can change independently of each other, resulting in different ratios of these two YAN components. Analysis of only alpha-amino nitrogen or only ammonia nitrogen does not provide an accurate indication of total nitrogen status for a given must.

The following graphs illustrate the differences in Chardonnay and Cabernet Sauvignon grape YAN levels in a hot vintage (2024) compared to cooler vintages (2023 and 2025). Typically, YAN increase slowly during maturation. In 2025, Chardonnay YAN was static and only had a slight increase as the fruit matured. Whereas the Cabernet Sauvignon had a reduction as the fruit matured. Loss of berry water can result in concentration of grape metabolites, including YAN. Many factors, including ground water, previous vintage harvest dates, and vineyard practices can impact the amount of YAN in grapes.

YAN

YAN

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CHA RDONNAY MULTI VINTAGE

CAB ER NET SAUVIGNON MULTI VINTAGE

AMMONIA Ammonia is the form of nitrogen nutrition most easily assimilated by yeast. Wineries routinely supplement nitrogen deficient musts with diammonium phosphate at the start of, or during fermentation to provide adequate nitrogen levels.

The following graphs illustrate the differences in ammonia levels in Chardonnay and Cabernet Sauvignon grapes between a hot vintage (2024) and cooler vintages (2023 and 2025). Ammonia levels generally decrease or stay flat during maturation. In 2025, Chardonnay ammonia mirrored the 2023 vintage, with a higher rate of decrease than observed in the warmer 2024 vintage. Ammonia levels were lower in the 2025 Chardonnay as the fruit matured. In the Cabernet Sauvignon, the 2025 vintage had comparatively lower ammonia values than the 2023 and 2024 vintages.

AMM ONI A

AM M ONI A

C HA RDONNAY MULTI VINTAGE

CAB E RNET SAUVIGNON MULTI VINTAGE

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N O PA Amino nitrogen, otherwise referred to as NOPA, is determined using a method specific for alpha amino groups. It is a measurement of primary amino acids usable by yeast. NOPA generally trends upward and is usually the largest component of the YAN. NOPA levels generally increase during maturation due to protein synthesis and accumulation. Increases toward the end of harvest could be due to berry water loss.

These graphs illustrate the differences in Chardonnay and Cabernet Sauvignon grape NOPA levels in a hot vintage (2024) versus cooler vintages (2023 and 2025). In 2025, Chardonnay NOPA increased, but at a slower rate than observed in 2023 and 2024. NOPA was static in the Cabernet Sauvignon grapes with very little increase observed as the fruit matured. These trends in NOPA accumulation are reflected in the YAN values for 2025.

NOPA CHA RDONNAY MULTI VINTAGE

NOPA

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CAB ERNET SAUVIGNON MULTI VINTAGE

ACID BALANCE

Vintage variations in any of the components that impact acid balance can result in unexpected changes in the final pH and tartaric acid (TA) of a wine. Monitoring the parameters that contribute to pH and TA is an important preview to how the vintage will affect overall acid balance in the wine.

In most years, juice pH is a function of potassium and malic acid levels. Warm vintages are usually associated with higher potassium and lower malic, resulting in higher pH wines. These graphs illustrate the differences in Chardonnay and Cabernet Sauvignon grape pH levels in a hot vintage (2024) versus cooler vintages (2023 and 2025). In both varietals, pH was higher in 2024. The 2023 vintage was slightly cooler than 2025, and the pH reflects that weather trend with slightly lower pH values observed.

CHARDONNAY MULTI VINTAGE PH

PH

CAB ER N ET SAUVIGNON MULTI VINTAGE

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TA R TA R I C AC I D TA is one of two major organic acids found in grapes. It accumulates in grape tissue early during development and declines during ripening due to berry growth and dilution. TA is not usually metabolized in grapes, although it can be metabolized in very hot weather.

These graphs illustrate the differences in Chardonnay and Cabernet Sauvignon grape tartaric acid levels in a hot vintage (2024) versus cooler vintages (2023 and 2025). In both varietals, tartaric acid declined and overall showed a similar vintage profile to that observed in the Chardonnay fruit.

In 2023, TA levels started higher and were similar at harvest to the 2024 vintage. In 2025, the TA levels more closely mirrored 2024, but finished lower.

TAR TAR IC

TAR TAR IC

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C HA RDONNAY MULTI VINTAGE

CABERNET SAUVIGNON MULTI VINTAGE

MA L I C AC I D Malic acid accumulates early in berry development and declines during ripening due to dilution and respiration. Warmer vintages tend to have lower malic acid levels, as there is more respiration with smaller differences in diurnal temperature shifts. The malic acid levels observed in the 2025 Chardonnay grapes at harvest were much lower than the hotter 2023 vintage. Examination of the weather data indicated there were smaller diurnal temperature shifts between May and October of 2025, compared to 2023, indicating warmer nights. This likely resulted in an increase of malic acid degradation through respiration in the Chardonnay. Malic acid in Cabernet Sauvignon grapes were as expected, with the lowest levels observed in the hotter 2024 vintage. The 2023 vintage was cooler and had the highest malic acid levels. In 2025 Cabernet Sauvignon had intermediate levels of malic acid, likely due to warmer evenings than 2023, and more dilution that 2024.

MAL IC

MAL IC

CHA RDONNAY MULTI VINTAGE

CAB ERNET SAUVIGNON MULTI VINTAGE

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P OTA SS I U M Potassium is the primary cation present in grape tissue. Potassium concentration in the berry is a function of root uptake and translocation. Both are strongly affected by viticultural factors including choice of rootstock, potassium fertilization, and canopy management. The following graphs illustrate the differences in Chardonnay and Cabernet Sauvignon grape potassium levels in a hot vintage (2024) versus cooler vintages (2023 and 2025). In both varietals, potassium was higher in 2024. The 2023 vintage was slightly cooler than 2025, and the potassium reflects that weather trend, with slightly lower values observed in the Cabernet Sauvignon. In the Chardonnay, the reduced diurnal temperature shift in October may have slowed down potassium movement into the berries.

P OTASSIUM

P OTASSIUM

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C HA RDONNAY MULTI VINTAGE

CABERNET SAUVIGNON MULTI VINTAGE

JUICE SCORPIONS Incoming fruit serves as the most important vector for introduction of indigenous microbes into the winery. These microbes are often associated with sluggish fermentations and volatile acidity (VA) problems.

Identifying and quantifying yeast and bacteria impacts on the fermentation performance and that can cause spoilage during the winemaking wine sensory attributes. process is the first step in preventing these Large numbers of acetic acid bacteria spoilage problems. on incoming fruit can carry through the Using Scorpions™ to see the full picture of fermentation and cause problems with VA spoilage microbes in the juice gives winemakers production when exposed to air during barrel better situational awareness. Potential problems aging. can be identified during the cold soak process, in EFFECTS O N FERMEN TATIO N stuck or sluggish fermentations, or during wine In addition to causing sensory impacts, large aging. populations of wild yeast can deplete the YAN VO L ATI L E AC I D I T Y I N J UI C E in the must, resulting in a YAN deficiency VA, measured as acetic acid, can be formed for the Saccharomyces cerevisiae driving the throughout the winemaking process. Both fermentation. Winemakers who detect high acetic acid bacteria and strains of wild yeast – levels of Hanseniaspora or Pichia in a must particularly Hanseniaspora and Pichia – are usually recheck YAN before yeast inoculation, commonly linked to VA production prior to and and supplement YAN if necessary. in the early stages of fermentation.

Likewise, if the Scorpions™ assay detects Elevated VA levels often occur during the heterofermentative lactic acid bacteria, such cold soak process, or between cold soak and as Lactobacillus brevis, L. kunkeei, L. hilgardii, fermentation during red wine production. The L. fermentum, and Oenococcus oeni, in a juice, VA-producing spoilage microorganisms grow winemakers usually increase their monitoring of quickly during this time, producing increasing malic acid and microbe levels if the fermentation levels of acetic acid until fermentation conditions becomes sluggish or stuck. Early identification inhibit their growth. of these bacteria and recognition of the risk they pose to difficult fermentations are key to Production of high levels of volatile acidity prior preventing VA formation in stuck fermentations. to fermentation can also cause problems later in the production process, including possible 18

Non-Saccharomyces

YEASTS DIAGNOSTICS

Several providers of commercial yeast to the wine industry offer strains of non-Saccharomyces yeast for use in the winemaking process. These yeasts can be used as bioprotective agents to reduce the impact of indigenous nonSaccharomyces strains as well as a way to reduce SO₂ use prior to fermentation. In addition, these yeast strains may provide improvements via increased acidity, aroma, complexity, structure, and mouthfeel.

to detect the presence of the individual strains; Metschnikowia pulcherrima, Lachancea thermotolerans, Torulaspora delbrueckii, and Pichia kluyveri.

The PCR-based diagnostics can be used to determine implant success with the individual strains. They can also be used with the ETS Juice Yeast Scorpion™ Panel to look at the efficacy of these strains at reducing levels of Hanseniaspora uvarum and Pichia membranifaciens, commonly In response to the increased use of these yeast observed in must samples. The diagnostics can strains by our clients, ETS Laboratories has be requested for individual yeast species, or as a developed a series of PCR-based diagnostics complete panel.

W H AT W E ' R E L O O K I N G F O R . . .

N O N - S A C C H A R O M YC E S Y E A S T PA N E L

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•

Metschnikowia pulcherrima

•

Torulapsora delbrueckii

•

Lachancea thermotolerans

•

Pichia kluyveri

Yeast Viability by

Flow Cytometry The concentrations of total and viable yeast are important indicators of fermentation health. Flow cytometry provides a rapid and accurate means to monitor the concentration and viability of yeast throughout the fermentation process. ETS Laboratories’ new automated analysis uses Flow Cytometry and the widely accepted dye exclusion method to determine cellular viability. Live yeast cells have selective cell membranes that exclude dye compounds. When a yeast cell dies, the membrane becomes permeable and allows dye to enter. Dead, or nonviable, cell DNA becomes stained and fluoresces. Individual cells are counted and photographed while passing through the flow cell. This automated method couples viability staining methods with advanced optics and flow cytometry to report total yeast count, precent budding, and precent viability.

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A Quantitative Analysis of Grapevine Red Blotch Associated Virus in Napa Valley: IMPACT OF VIRAL LOAD ON FRUIT CHEMISTRY

G

rapevine red blotch disease (GRBD) is a major vineyard viral disease impacting the wine industry. The disease is caused by the Grapevine red blotch associated virus (GRBV).

Published estimates indicate financial losses ranging from $2,231 to $68,548 per hectare over the expected 25-year productive lifespan of a vineyard. This figure is based on losses due to impact on fruit quality and yield, cost of removing and replanting a vineyard, and the lost income from vineyards that do not produce useable fruit during the initial years after replanting. Current guidelines for vineyard GRBD management suggest removal of individual infected vines if the disease incidence is below 30% and complete vineyard removal if more than 30% of the vines are infected.

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Grapes from infected vines have a decrease in total soluble solids, suggesting interference in sugar synthesis and/or transport from leaves to berries. Additional impacts on fruit chemistry indicate a disruption of normal grape ripening events and an overall delay in fruit maturation.

For example, malic acid levels are often higher, resulting in increased titratable acidity. In addition, both potassium and anthocyanin levels can be reduced. Recent studies indicate the primary metabolic pathways associated with early berry development are normal in infected vines, whereas the primary metabolic pathways associated with ripening are inhibited in infected vines. GRBV impacts the vine by “silencing” genes in these metabolic pathways associated with ripening.

QUANTIF IC AT I O N O F G RBV I N GR A P E V I N E M AT E R I A L The two most commonly used DNA-based diagnostics to detect GRBV are Loop Mediated Isothermal Amplification (LAMP) and Polymerase Chain Reaction (PCR). In this study, Quantitative Polymerase Chain Reaction (qPCR) was used for DNA-based quantification of GRBV in vine material.

The qPCR diagnostic assay can provide a numerical output indicating the number of viral copies per milligram of tissue. The qPCR method requires a DNA isolation and purification step, as well as higher-cost equipment and reagents as compared to LAMP

or end-point PCR. However, it can be used to determine the actual number of viral copies in the vine material tested. ETS Laboratories has developed and validated a qPCR diagnostic assay for GRBV. This is the first commercially available GRBV qPCR assay and can report as little as 10 viral copies per milligram of tissue. Internal testing indicates this is at least 10x more sensitive than LAMP and not prone to the falsepositive and false-negative results sometimes observed with the LAMP method.

2025 HARV E S T NAPA VALLE Y GR A P E V I N E R E D B LOTC H V I R U S ST U DY ETS Laboratories initiated a collaborative study with eight Napa Valley Vineyards during the 2025 harvest to investigate GRBV in the vineyards. One part of the study focused on investigating the impact of viral load on fruit chemistry. The ETS Juice Panel and Red Grape Phenolic Panel were used to determine if there was a correlation between viral load and impact on fruit chemistry.

Information on the vineyards participating in the study is as follows: • Cabernet Franc, 7-year-old vineyard, Clone 327, 039-16 Rootstock • Cabernet Franc, 20-year-old vineyard, Clone 214, 3309C Rootstock • Cabernet Sauvignon, >30-year-old, unknown clone, St. Georges Rootstock • Cabernet Sauvignon, 12-year-old, Clone 7, 039-16 Rootstock • Cabernet Sauvignon, 14-year-old, Clone Entav 15, 420A Rootstock • Merlot, 4-year-old, Clone 181, 1616 Rootstock • Malbec, 5-year-old,Clone 598, GRN-1 Rootstock • Zinfandel, 53-year-old, Werle Clone, St. George Rootstock The initial step in each vineyard was to screen a basal leaf petiole from 30 to 40 vines post veraison. Vines were selected based on symptoms and/or available LAMP results. The goal was to identify three vines from each of the following categories; non-detectable, low viral load, moderate viral load, and high viral load. Based on the initial screening for the eight vineyards, we observed some vineyards did not have any vines in the “low” category, and an additional category was designated for “moderate-high.” The following viral load levels were assigned to the individual categories: • <10 copies/mg = non-detectable • 10-500,000 copies/mg = low • 500,000-5,000,000 copies/mg = moderate

• •

5,000,000-20,000,000 copies/mg = moderate-high >20,000,000 copies/mg = high

Three vines per vineyard for each of four viral load categories were selected for the study based on the initial screen. Vines selected for the study were sampled two weeks later to map viral distribution within the vines. Basal leaf petioles from six individual canes, randomly selected and evenly distributed on the vine, were sampled and tested for viral load. Fruit from the selected vines was harvested 1 to 3 days before the vineyard was harvested, and composites were made from clusters on the same vine for fruit chemistry analysis.

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Examples of GRBV viral load impact on fruit chemistry from a sample of the vineyards participating in the trial.

Merlot, 4-years old, Clone 181, 1616 Rootstock Pooled data for the Juice Chemistry Panel Results from three vines each for non-detectable (N), moderate (M), moderate-high (MH) and high (H) viral load categories.

Sample

Brix

Malic

pH

K

Tartaric

TA

YAN

Catechin

Tannin

Tot Poly CAT:TAN Antho Antho

mg/L

g/L

g/L

mg/L

mg/L

mg/L

mg/L

mg/L

PA:TAN

Quercetin

GRBV Load

mg/L

copies/mg

Description degrees

g/L

Merlot N Pool Average

23.4

1.29

3.34

1800

8.5

6.3

88

36

225

0.160

908

10

0.045

72

<10

Merlot M Pool Average

21.2

1.72

3.24

1750

9.3

7.5

113

35

207

0.171

772

9

0.045

42

1,738,900

Merlot MH Pool Average

19.9

1.87

3.21

1710

9.3

7.8

103

35

222

0.158

670

10

0.043

44

13,467,000

Merlot H Pool Average

19.5

2.17

3.29

1830

8.9

7.6

131

45

206

0.218

600

9

0.044

44

29,023,000

The moderate-high and high viral load vines had a 3 to 4 °Brix drop in sugar accumulation and 0.6 to 0.9 g/L more malic acid than the non-detectable vines. In addition, the moderate, moderate-high, and high viral load vines had a 24 to 34% drop in anthocyanin compared to the non-detectable vines.

Cabernet Sauvignon, 12-years old, Clone 7, 039-16 Rootstock Pooled data for the Juice Chemistry Panel Results from three vines each for non-detectable (N), low (L), moderate (M) and high (H) viral load categories.

Sample

Brix

Malic

Description

degrees

g/L

Cab Sauv ND Pool Average

26.8

1.6

Cab Sauv L Pool Average

27.1

Cab Sauv M Pool Average Cab Sauv H Pool Average

pH

K

Tartaric

TA

YAN

Catechin Tannin

mg/L

g/L

g/L

mg/L

mg/L

mg/L

3.58

2040

7.1

5.0

63

13

435

1.5

3.57

2040

7.0

5.1

53

12

19.6

1.7

3.24

1750

8.8

7.2

38

20.6

1.7

3.33

1886

8.3

6.7

43

Tot Poly CAT:TAN Antho Antho PA:TAN Quercetin mg/L

mg/L

0.032

900

26

451

0.026

935

16

647

0.024

13

551

0.023

GRBV Load

mg/L

copies/mg

0.060

42

<10

26

0.058

43

30

824

27

0.042

78

3,044,600

754

24

0.044

55

3,708,200

The moderate and high viral load vines had an approximate 6 to 7 °Brix drop in sugar accumulation compared to the non-detectable and low vines. In addition, the moderate and high viral load vines had a 14% drop in anthocyanin compared to the non-detect and low vines. The moderate and high viral load vines also had a decrease in potassium indicating delayed ripeness as compared to the non-detectable vines.

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Cabernet Sauvignon, >30-years old, unknown clone, St. Georges Rootstock Pooled data for the Juice Chemistry Panel Results from three vines each for non-detectable (N) and high (H) viral load categories Sample

Brix

Malic

Description

degrees

g/L

Old Cab N Pool Average

26.9

1.21

Old Cab H Pool Average

21.3

1.80

pH

K

Tartaric

mg/L

g/L

3.67

2175

3.35

1800

TA

YAN

Catechin

Tannin

g/L mg/L

mg/L

mg/L

6.8

4.8

88

20

587

8.3

7.0

122

30

391

Tot Poly CAT:TAN Antho Antho PA:TAN Quercetin mg/L

mg/L

0.032

738

28

0.086

525

18

GRBV Load

mg/L

copies/mg

0.048

55

<10

0.046

54

10,414,000

The high viral load vines had an approximate 5.6 °Brix drop in sugar accumulation and 0.59 g/L more malic acid than the non-detectable vines. In addition, the high viral load vines had a 29% drop in anthocyanin compared to the non-detect vines. The high viral load vines also had a decrease in potassium and increase in catechin, both indicating delayed ripeness as compared to the non-detectable vines.

Cabernet Franc, 7-years old vineyard, Clone 327, Rootstock 039-16 Pooled data for the Juice Chemistry Panel Results from three vines each for non-detectable (N), moderate (M), moderate-high (MH) and high (H) viral load categories.

Sample

Brix

Malic

pH

K

Tartaric

TA

YAN

Catechin

Tannin

Tot CAT:TAN Antho

Poly Antho

mg/L

g/L

g/L

mg/L

mg/L

mg/L

mg/L

mg/L

Description degrees

g/L

Cab Franc N Pool Average

25

1.32

3.67

2333

7.4

4.5

77

9

331

0.028

750

17

Cab Franc M Pool Average

21

1.86

3.59

2275

7.5

5.3

57

15

379

0.039

492

Cab Franc MH Pool Average

20

1.83

3.41

2100

8.3

6.4

73

21

433

0.051

Cab Franc H Pool Average

21

1.95

3.59

2217

7.0

5.2

60

13

466

0.028

PA:TAN

Quercetin

GRBV Load

mg/L

copies/ mg

0.051

85

<10

14

0.036

99

19,060,000

402

12

0.028

83

27,264,000

449

13

0.029

77

45,351,000

The moderate, moderate-high and high viral load vines had a 4-5 °Brix drop in sugar accumulation and 0.5-0.6 g/L more malic acid than the non-detect vines. In addition, the moderate, moderate-high and high viral load vines had a 34-46% drop in anthocyanin as well as an 18-29% drop in polymeric anthocyanins compared to the non-detect vines.

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SUMMARY O F RE S U LT S F RO M T H E E I GH T VINEYARDS PART I C I PAT I N G I N T H E ST U DY. Values represent the percent change in high viral load vines compared to non-detectable viral load vines. Negative values indicate a decrease, while positive values indicate an increase associated with high viral load TA

Tot Antho

Poly Antho

mg/L

g/L

mg/L

-7%

25%

-19%

-6%

-37%

-35%

3,708,200

33%

-10%

31%

-41%

-53%

63%

-4%

21,500,000

-8%

27%

-3%

-6%

-41%

-2%

10%

3%

12,873,000

Zinfandel - 53 Years Old

-12%

27%

7%

-13%

-33%

-10%

-184%

-10%

18,461,000

Malbec - 5 Years Old

0%

31%

4%

2%

-60%

-29%

18%

1%

26,077,000

Merlot - 4 Years Old

-20%

40%

-1%

16%

-51%

-11%

27%

-2%

29,023,000

Cab Franc - 7 Years Old

-20%

32%

-2%

13%

-67%

-28%

0%

-75%

45,351,000

Cab Sauv > 30 Years Old

-21%

49%

-9%

46%

-29%

-35%

167%

-4%

10,414,000

Sample

Brix

Malic

Description

degrees

g/L

Cab Sauv - 12 Years Old

-30%

8%

Cab Sauv - 14 Years Old

-26%

Cab Franc - 20 Years Old

pH

CAT:TAN

PA:TAN

GRBV Load copies/mg

A decrease in °Brix was observed in high viral load vines across all vineyards except the Malbec vineyard. All eight vineyards showed an increase in malic acid in high viral load vines. Similarly, all vineyards exhibited reductions in both total and polymeric anthocyanins in vines with high viral load.

A 20-year old Cabernet Sauvignon vineyard was surveyed for the project and not included as there were no vines in the non-detectable category observed. However, the vines had a higher crop load, enabling a comparison of fruit chemistry variation within a single vine.

Sample

Brix

Malic

Description

degrees

g/L

CS Vine M2, Cane 2

23.4

1.75

CS Vine M2 5 Cane Pool

21.8

2.23

pH

K

TA

Catechin

Tannin

mg/L

g/L

mg/L

mg/L

3.52

1950

5.5

22

947

3.4

1750

6.1

31

712

CAT:TAN

Tot Antho

GRBV Load

mg/L

copies/ mg

0.023

975

364,600

0.044

843

2,518,000

Fruit was pooled from a single cane in the low viral load category and compared to fruit pooled from five canes on the same vine in the moderate viral load category. Fruit chemistry parameters from the moderate viral load category canes indicated a delayed ripening. This included a decrease in °Brix, pH, potassium, tannin and total anthocyanins. Likewise, an increase in malic acid, TA, catechin and the catechin/tannin (CAT:TAN) ratio in the moderate viral load category canes also supported delayed ripening.

This was the first study investigating GRBV viral load impact on fruit quality in the Napa Valley.

Although the study only included eight vineyards and five varietals, similar trends were observed in the fruit chemistry response to GRBV viral load in all vineyards. The results show GRBV has an impact on fruit chemistry consistent with those observed with delayed ripening. Increases in GRBV viral load resulted in larger changes in °Brix, malic acid and total anthocyanins The results of this study demonstrate the effectiveness of the ETS GRBV qPCR diagnostic as a tool to provide a new, quantitative way to look at the impact of GRBD in the vineyard.

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VOLATILE ACIDITY THE TWO COMPONENTS COMMONLY ASS O C I ATED W I TH “VA TAIN TS,” ACETIC AC ID AND ETH YL AC ETATE, CAN B E FO R M ED BY BOT H YEA S T A ND B ACTER I A. I N THE C A SE OF B AC TER I A , I T CAN B E FO R MED WI TH OR W I T HO U T OX YG EN P R ESEN T.

VOLAT ILE AC I D I T Y ( VA )

VA is strictly speaking a measure of the volatile acids in wine, although in the real world the contribution of volatile acids other than acetic acid is negligible. VA is a normal component of wines at moderate levels (normal concentrations range from 0.3-0.9 g/L of acetic acid), but very quickly becomes undesirable as levels rise. The sensory threshold is around 0.9-1.0 g/L, depending on the wine style. In the United States, regulatory limits are 1.2 g/L in white wine and 1.4 g/L in red wine.

COLD SOAK / EARLY S TAG E FE RMENTAT IO N Acetic acid can be produced prior to fermentation by Acetic Acid Bacteria and wild yeast in compromised fruit.

It’s unusual to see alcohol present in juice before fermentation, but if clusters experience fungal rot or other types of damage (such as bird or insect damage), wild yeast in the vineyard can begin fermenting the juice that is leaked out. Acetic Acid bacteria can then convert the alcohol to acetic acid, causing “sour rot” and leading to high VA levels before fermentation has even begun.

Ethyl acetate is often produced in the early stages of fermentation and can be a particular problem in native fermentations with a slow start. Native yeast, especially Hanseniaspora, are the main Ethyl Acetate producers at this stage. Note that the Hanseniaspora can consume most or all of the YAN in the must very early in the fermentation, although they will only produce alcohol up to around 6%. High levels of Hanseniaspora and low YAN concentrations can contribute to stuck fermentations.

E TH Y L AC E TATE

From a chemistry standpoint, ethyl acetate is not a component of VA, as it is an ester and not an acid.

However, as an ester formed by ethanol and acetic acid, it is often linked to increased production of VA. From a sensory point of view, ethyl acetate is often classified as a “VA taint,” and its “nail polish remover” odor is often a telltale sign of high VA. Similar to acetic acid, there is a fine line between complexity and spoilage Low levels of ethyl acetate can contribute “fruitiness/ sweetness” as well as other positive characteristics to a wine. Normal concentrations are usually less than 100 mg/L, while the sensory threshold is generally 130-150 mg/L, depending on the wine style.

P R I M A RY F E R M E N TATI O N

Acetic acid production in primary fermentation is generally caused by yeast, including Saccharomyces and other species, but can also be formed by bacteria.

The native yeasts Hanseniaspora and Pichia can drive fermentations up until around 6-7% alcohol, at which point they become stressed by the alcohol.

Saccharomyces is more competitive as it is tolerant to and produces higher alcohol levels. In certain situations, the native yeasts respond to the changing fermentation conditions by producing elevated levels of acetic acid.

Bacteria, usually Lactobacillus, can also generate acetic acid from sugar and can often produce high levels of VA in stuck and sluggish fermentations.

Oenococcus oeni, the bacteria used for inoculating most malolactic fermentations can also produce acetic acid from fructose. This frequently occurs at the end of malolactic fermentation if there is still fermentable sugar remaining in the wine.

Ethyl acetate production during fermentation is significantly impacted by the yeast strain and fermentation temperature. Although Saccharomyces cerevisiae will produce ethyl acetate, research has indicated that some of the Saccharomyces bayanus strains are more likely to form ethyl acetate in cold fermentations.

POTENTIAL ALCOHOL T H E A M O U N T O F FER M EN TAB L E SU GA R (GLUCOSE A ND F RUC TOSE) IN JUIC E AN D T H E AV ER AG E CO N V ER SI O N R ATE OF SUGA R INTO A LCOHOL C A N BE USED TO P RED I C T TH E P OTEN TI AL ALCO HO L LEVEL IN WINES.

HOW ACCURATE ARE POTENTIAL ALCOHOL ESTIMATES? Our clients have reported that glucose and fructose values improve the quality of their predictions. However, it is important to remember that yeast populations and fermentation conditions vary, and any prediction of potential alcohol is only an approximation. Alcohol conversion ratios can vary, so it is possible your actual alcohol may be lower or higher than the estimate.

Many of our clients have found that the conversion rates observed for their own yeasts and fermentation conditions remain relatively constant, and they use their internally observed conversion rates to calculate potential alcohol content based on their glucose and fructose values.

With white wines, predictions are usually fairly accurate. With red wine, however, getting a truly

representative juice sample can be a challenge and can affect potential alcohol predictions. A juice sample taken soon after a tank is filled may not take into account un-popped berries, unripe berries (less sugar and more acids), and raisins (sometimes an overlooked source of large amounts of sugar, acid, and potassium).

We suggest sampling after an initial 10 °Brix drop, and analyzing the fermenting sample for glucose and fructose and alcohol simultaneously for a more accurate potential alcohol estimate. Proper sample preparation is key to accurate results. At ETS Laboratories, juice samples are centrifuged before analysis, then mixed by inversion to avoid stratification toensure the most accurate results.

Particulates have a minimal impact on refractometry, but can have a large impact on densitometry results.

WHAT’S THE BEST WAY TO PREDICT POTENTIAL ALCOHOL LEVELS? Predicting potential alcohol levels in finished wines sounds simple, but there is more than one way to measure “sugar,” and formulas to convert this sugar into potential alcohol often miss the mark.

The “old school” method was to multiply °Brix by 0.6.

One °Brix is defined as 1 gram of sucrose in 100 grams of aqueous solution. However, grape juice does not naturally contain sucrose, but rather glucose, fructose, and a variety of organic acids and other dissolved solids. When used for grape juice, °Brix is only an approximation of dissolved sugar, not an accurate representation of the fermentable sugars, and using ºBrix for estimating potential alcohol adds an additional layer of uncertainty to alcohol predictions. Differences between ºBrix and actual fermentable sugar content are even more pronounced in high ºBrix fruit and in fruit affected by fungal growth.

How ºBrix is measured also has an influence. Differences exist between ºBrix by refractometry, densitometry 27

(using either hydrometers or digital instruments), and other secondary measurements. The differences among the various measurement techniques are quite unpredictable depending on sample composition.

A modern calculation that has proven to be more accurate uses glucose and fructose analysis, which provides a more accurate measurement of fermentable sugar levels compared to using ºBrix.

Note that in ripe fruit, glucose and fructose numbers often appear higher than the corresponding ºBrix results, because ºBrix is measured as a percentage by weight, meaning ºBrix values are greatly influenced by the density of the juice, while glucose and fructose are measured as weight by volume and is independent of juice density.

An official conversion rate formula used in Europe is: Potential Alcohol (% vol) = glucose+ fructose (g/L) / 16.83. In practice, rounding the 16.83 conversion factor to 17 is common.

SUGAR ANALYSIS I N T H E W I N E IN DUSTRY, A TER M LIKE “SUGA R” C A N MEA N DIF F ERENT T H I N G S . C L I EN TS O FTEN R EQ UEST T ESTING FOR “RS, ” BUT THIS TERM C A N BE V ERY A M B I GUO US.

°BRIX

G LU COS E + F R U C TOSE

°Brix is a measurement of the apparent concentration of sugar. It is commonly used for grape juice and must and is expressed as a percentage by weight (% w/w).

One °Brix is defined as 1 gram of sucrose in 100 grams of aqueous solution. When the solution contains dissolved solids other than pure sucrose, as is the case for grape juice and must, the °Brix is only an approximation of dissolved sugar.

In grape juice, glucose + fructose analysis measures the combined concentrations of the two main sugars present that can be consumed by yeast, also known as “fermentable sugars.” Compared to °Brix, Glucose + Fructose can provide a better estimate of potential alcohol concentration after fermentation. In wine, “residual sugar” usually refers to the sum of glucose + fructose, an indication the amount of fermentable sugars remaining post fermentation, which is also an indication of ‘dryness.’

GLUCOS E AND F RU C TOS E PANE L

Sucrose is not captured by this test. If it has been used in the winemaking process (such as for chaptalization of must, secondary fermentation of sparkling wine or added as a sweetener) measurement of glucose + fructose alone is usually not adequate – instead see Glucose + Fructose (Inverted)

The Glucose and Fructose Panel provides the individual levels of glucose and fructose, in addition to their combined concentration. This test is often requested to investigate or remedy stuck or sluggish fermentations.

R EDUCIN G SU G AR Historically, “Residual Sugar” was measured by the Reducing Sugar method. This test derives its name from the ability of most sugars in juice or wine to ‘reduce’ other compounds. The most common reducing sugars are glucose and fructose.

However, the method does not distinguish between fermentable sugars, non-fermentable sugars, or other ‘reducing’ compounds, and these other compounds may contribute to the reported results.

Because of these limitations, the Reducing Sugar method is no longer the preferred choice to monitor completion of primary fermentation.

G LU COS E + F R U C TOSE ( I N V E RTED ) Inverted Glucose + Fructose provides the sum of the concentrations of glucose and fructose after “inversion” of the sample. Inversion is a process where sucrose is broken apart into glucose and fructose, so that it can be measured and included in the reported results. Hence, this test is useful when “residual sugar” is required after chaptalization of must, secondary fermentation of sparkling wines, or whenever sucrose has been used as a sweetener in wine, spirits, or other alcoholic beverages.

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BUILDING A PHENOLICS PROGRAM ETS LAB O RATO RI E S OF F E R S A F U L L SU I T E O F A DVA N C E D HPLC -B AS E D ANALY T I C A L TO O L S TO E VA LUAT E P H E N OL I C CO M P O U N D S I N G RAP E S, JU I C E , F E R M E N T I N G M U ST A N D WIN E . O U R RAN G E O F P H E N O L I C A N A LYSE S A L LOW S F L E XI B L E USE AND I M P LE M E N TAT I O N TO SU I T I N D I V I D UA L N E E D S.

V I N E YA R D D E C I S I O N S

G R A P E P H E N O L I C PA N E L

Phenolic compounds in red wine grapes are directly linked to eventual wine flavor, color and aging characteristics.

The grape phenolic panel can characterize site-tosite variation as well as within-site differences. It works well as a prediction tool for describing vintage effects on potential phenolics and is a great tool for vineyard research projects. It is very sensitive to changes in phenolic compounds occurring during grape maturation. The changes in grape tannin are particularly important for red wine picking decisions. The grape phenolic panel can track changes in seed ripening, skin tannin extractability and tannin modification. Dilution and concentration effects on tannin and other phenolic components can be monitored with the Grape Phenolic Panel particularly when used in conjunction with Grape Water Content.

29

U N D E R S TA N D I N G R AW M AT E R I A L S

G R A P E P H E N O L I C PA N E L

Successful winemaking strategies require accurate information on grape composition. Winemakers use this panel during fermentation to reach target levels of tannin for specific wine styles, monitor seed extraction, adjust tannin modification through oxygenation and decisions on extended maceration and pressing.

M A N AG I N G F E R M E N TAT I O N

R A P I D P H E N O L I C PA N E L F O R W I N E

Phenolic compounds are extracted from grapes during fermentation and maceration. Monitoring the phenolic composition of the must during fermentation can greatly enhance a winemaker’s control of the process.

Juice bleeds, fermentation temperatures, pump-over or punch down regimes, the use of rack-and-return, oxygen or air additions and press timings can all be fine-tuned with feedback on changes in phenolic composition. With this information, winemakers can adapt winemaking practices to fit the vintage and successfully create wines of a target style.

S E T T I N G TA R G E T S

R A P I D P H E N O L I C PA N E L

Phenolic composition is one of the main components of red wine style. The amount of tannin and its composition is the foundation of a wine’s structure.

There are no “correct” values for these parameters. A winery must define their own style as a brand and for individual products within that brand.

Integrating phenolic information into stylistic choices requires an understanding of the impact of tannin on the sensory profile of wines. For a winery new to this information a good strategy is to analyze a selection of recent products. Recent production lots, finished wines and competitor’s products are good choices. Tasting products with analytical information allows winery staff to build the connections between taste and analytical information. Taste is the final arbiter of style but a clear understanding of the relationship of taste and analysis is needed to turn analytical information into action.

W I N E LOT C H A R AC T E R I Z AT I O N

R A P I D P H E N O L I C PA N E L

After the completion of fermentation/maceration, a wine lot typically represents a specific vineyard and fermentation tank. This is an excellent point for collecting quality control data. A comprehensive review of production lots is a powerful tool for monitoring block to block variation and the effects of winemaking practices. Analysis of finished production lots early in the vintage is very useful for changing fermentation practices and targets later in the vintage.

BLENDING

R A P I D P H E N O L I C PA N E L F O R W I N E O R R E D WINE PHENOLIC PROFILE

Winemakers interested in consistent tannin and color levels benefit by comparing the phenolic profiles of bulk wines prior to blending. Potential blends can be compared to target phenolic levels and benchmarks prior to final blend.

B OT T L E D W I N E C H A R AC T E R I Z AT I O N

RED WINE PHENOLIC PROFILE

Many wineries establish quality control benchmarks for phenolic content immediately after bottling.

This is especially useful for determining product consistency and for monitoring wine development during aging.

F I N I S H E D W I N E E VA LUAT I O N S

RED WINE PHENOLIC PROFILE

A historical review of products from within a winery and evaluation of similar products from other producers is an excellent way to establish phenolic benchmarks. This is often the first step in building an integrated program of phenolic analyses. A careful review of finished wines combined with sensory evaluation and market feedback can identify program strengths and weaknesses. The identification of desirable levels for key phenolic components creates targets that can be incorporated into process control points in the vineyard and winery.

30

PHENOLIC MATURITY THE ETS RE D G RAP E P H E N O LI C PA N E L

Traditionally, harvest decisions are based on technological maturity: sugar levels, titratable acidity, and the pH of grape juice. However, these measurements only reflect the ripeness of the grape pulp, and do not reveal the maturity of the skins and seeds, known as phenolic maturity.

Importantly, technological and phenolic maturity rarely occur at the same time.

Since the early 2000s, ETS Laboratories has offered testing for phenolic maturity through its Red Grapes Phenolic Panel. This test is based on the partial extraction of berry samples, designed to simulate the extraction of phenolic compounds under winemaking conditions. The resulting extracts are analyzed using High Performance Liquid Chromatography (HPLC).

31

A key strength of our HPLC method is its ability to measure, in a single run, various classes of complex polyphenols—such as anthocyanins, tannins, and anthocyanin-tannin complexes (also known as polymeric anthocyanins)—as well as monomeric compounds like catechin, which serves as a marker for seed-derived phenolics. This unique capability provides valuable insights for both growers and winemakers.

The Red Grape Phenolic Panel is commonly used to: •

Track phenolic maturity and decide the best harvest time

•

Assess grape potential for specific wine styles and price points

•

Identify and improve under-performing vineyards

•

Evaluate vintage differences

•

Support informed grape purchasing decisions

•

Guide winemaking choices, such as whether to do a saignée, based on analytical evidence

PHENOLIC MATURITY IS NOT ONE PROCESS Phenolic maturity is often assessed by measuring a simple parameter, often total anthocyanins, in grape homogenates. However, this approach has several limitations:

The ETS Red Grape Phenolic Panel assesses the three distinct components of Phenolic Maturity: anthocyanins, skin-derived tannins, and seed-derived tannins

•

Anthocyanins and tannins develop differently; one cannot represent the other.

•

Phenolic maturity assessments should consider not just the total amounts of polyphenols in grapes, but also how easily they can be extracted in winemaking conditions.

•

The source of tannins matters; seed tannins are regarded as bitter and astringent, while skin tannins are considered “softer,” and are key to mouthfeel, volume, and length.

•

As grapes ripen, the extractability of skin and seed tannins changes in opposite directions.

In contrast, ETS Laboratories phenolics specialist Dr. Steve Price developed a partial extraction method followed by HPLC analysis, which has proven reliable and effective. It assesses the three key components of phenolic maturity—anthocyanins, skin tannins, and seed tannins. Additionally, it measures anthocyanintannin complexes (polymeric anthocyanins), previously thought to be created mainly during winemaking, but actually formed in significant quantities in grape skins during the late stages of ripening. The method also measures quercetin glycoside, a flavonoid produced by grapes for UV protection, which serves as a useful marker of sun exposure.

Parameter Reported

Comments

Low

High

Catechin

From seeds: Marker of seed maturity

10

100

Tannins

Total tannins from both skins (“softer”) and seeds (“harsher”)

200

700

Polymeric Anthocyanins

“Polymeric Pigments”, “Bound Anthocyanins”, “Pigmented Tannins”: Markers of skin degradation

10

30

Total Anthocyanins

Free (unstable) + Polymeric (stable)

800

2000

Catechin / Tannin

Tannin “seediness” index

0.020

0.200

Polymeric Anthocyanins / Tannin

Tannin “modification” index

0.030

0.100

Quercetin Glycoside

Marker of sun exposure

50

200

Figure 1: Parameters reported in the ETS Red Grape Phenolic Panel, and typical ranges (mg/L) in Cabernet Sauvignon grapes “partial extracts” analyzed at ETS Laboratories. Note the wide ranges observed for all parameters.

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HOW DOES 2 025 CO M PARE TO T H E PA ST T W O V I N TAGE S? For the first time last year, ETS Laboratories presented comprehensive phenolic maturity data comparing the 2022, 2023, and 2024 vintages. This year, we continue this analysis by examining how the 2025 vintage compares to its two predecessors.

From the perspective of phenolic maturity, the past three vintages have once again displayed notable differences. These variations reflect not only the distinct climatic conditions during each growing season, but also the sometimes unpredictable behavior of the vines. The year-to-year differences are clearly illustrated by the data we collected, as shown in Figures 2 through 7, which highlight ripening trends in Cabernet Sauvignon grapes.

To recap, in 2023, California experienced cooler-than-usual conditions. This caused significantly delayed phenolic maturation: •

•

Catechin: Levels started high but gradually declined, indicating a delayed yet satisfactory seed hardening process.

•

Polymeric anthocyanins: Initially very low, and increasing only slowly during harvest, indicating that the skins were resisting senescence.

The Catechin/Tannin ratio started high but reached moderate levels as the season progressed.

In contrast, the Polymeric Anthocyanins/ Tannin ratio showed little change, reflecting a relatively stable contribution of skin tannins.

In 2024, the growing season commenced with belowaverage temperatures, followed by a pronounced heat event in June and a subsequent heat wave in early October that brought a sudden conclusion to the harvest. Despite considerable heterogeneity among the samples analyzed, we noticed phenolic maturity parameters advancing rapidly over the course of the season: •

Total anthocyanins: Fairly typical on average but exhibiting a wide range of values.

•

Tannin: Low in early September, suggesting that the seeds were already ripe, while the skins were not ready yet to release their tannins. However, skin tannin extractability increased steadily throughout the month.

Total anthocyanin: Levels were high overall, due to reduced degradation. In a typical year in warm climates, harvest begins after the anthocyanin concentration reaches its maximum (referred to as the “anthocyanin peak”), after which levels • generally decrease. However, 2023 was a notable exception, with anthocyanins continuing to rise throughout the harvest.

• Tannin: Low overall, while the trend observed in our data displayed a “U-shaped” curve, illustrating a first phase of decline in seed tannins, followed by an increase in the • extractability of skin tannins.

•

33

•

Catechin: Levels started at moderate values, indicating relatively early seed maturity, and continued to decrease steadily.

Polymeric anthocyanins: Started at lower levels but increased sharply in September, confirming rapid skin degradation and enhanced tannin extractability from the skins.

Both the catechin/tannin and polymeric anthocyanins/tannin ratios moved in the expected directions throughout September, indicating favorable maturation trends.

Figure 2: Total anthocyanins in Cabernet Sauvignon grape extracts across the 2023–2025 vintages. Anthocyanins generally decline during harvest, especially under warmer conditions, with the cool 2023 vintage as an exception. In 2025, despite another cool season, anthocyanins declined relatively rapidly.

Figure 3: Tannins in Cabernet Sauvignon grape extracts during the 2023, 2024 and 2025 vintages. In 2025, we saw a sharp increase, attributable to low seed tannins early in the season, followed by increased extractability of skin tannins.

34

Figure 4: Catechin in Cabernet Sauvignon grape extracts during the 2023, 2024 and 2025 vintages.

As seeds ripen, we always observe a decline during harvest season.

Catechin levels were particularly low overall during the 2025 vintage, indicating ripe seeds.

Figure 5: Polymeric Anthocyanins in Cabernet Sauvignon grape extracts during the 2023, 2024 and 2025 vintages. As skins degrade, tannins combine with anthocyanins, forming polymeric anthocyanins. In 2025, despite cool weather conditions, levels increased steadily.

The 2025 growing season was relatively cool overall, with no major heat events. From this perspective, it resembled 2023, but the similarities largely end there. Despite persistently low °Brix levels, all indicators of phenolic ripeness advanced rapidly: •

Total anthocyanins: Although values were highly variable early in the season, they declined at a relatively fast rate.

•

Tannins: Early- to mid-September levels were low, suggesting that seeds were already mature. This was followed by a sharp increase, indicating skin senescence and enhanced skin tannin extractability.

•

Catechins: Starting at low levels, confirming early seed maturity, catechin concentrations steadily declined throughout the season to remarkably low values.

•

Polymeric anthocyanins: Initially low, these increased sharply in September and October, confirming skin senescence and increased extractability of skin tannins.

•

Catechin/tannin and polymeric anthocyanins/tannin ratios: Both moved quickly over the season, highlighting the rapid progression of phenolic maturation.

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Figure 6: Catechin/Tannin ratios in Cabernet Sauvignon grape extracts during the 2023–2025 vintages. High Catechin/ Tannin ratios indicate a greater contribution of seed-derived tannins to total tannins and typically decline sharply during harvest. In 2025, these ratios were already low early in the season and continued to decrease, resembling the pattern observed during the much warmer 2024 vintage.

Figure 7: Polymeric Anthocyanins/Tannin ratios in Cabernet Sauvignon grape extracts during the 2023–2025 vintages.

Higher ratios indicate skin degradation and typically rise with extended hang time. In 2025, these ratios increased steadily, in contrast to the stalled progression observed in 2023.

In 2025, technological maturity measures indicated slow ripening, yet phenolic maturity was achieved with ease

Although the weather conditions in 2025 were comparable to 2023, grape ripening patterns were very different.

In 2023, clients submitted juice and berry samples late in the season. By then, technological ripeness measures like °Brix, TA, and pH were approaching typical harvest levels. Yet, phenolic maturity metrics largely lagged behind during the whole season.

In 2025, the opposite occurred: technological maturity measures indicated slow ripening, with °Brix remaining moderate even late in the season; yet phenolic maturity was achieved with ease. For winemakers, this meant extended macerations were generally safe, with little risk of extracting harsh seed tannins. However, long macerations were often not necessary, thanks to the abundance of readily extractable skin tannins.

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AROMAS NEW FO R 2026: THIOLS PANEL The ETS Thiols Panel measures three key volatile thiols: Originally discovered in Sauvignon Blanc, “varietal” thiols are now recognized as some of the most important aroma compounds in fresh, fruit-forward white and rosé wines. These highly potent molecules contribute desirable tropical fruit, citrus, and floral aromas while enhancing overall fruit expression, palate intensity, and finish.

4-Mercapto-4-methylpentan-2-one (4-MMP), also known as 4-methyl-4-sulfanylpentan-2-one (4MSP), is an exceptionally powerful aroma compound best known for contributing the distinctive varietal character of Sauvignon Blanc. It is associated with aromas of blackcurrant bud, boxwood, and broom.

3-Mercaptohexyl acetate (3-MHA), also known as 3-sulfanylhexyl acetate (3-SHA), contributes passion fruit, guava, and boxwood aromas. In addition to Sauvignon Blanc, it is a major contributor to the aroma profiles of many fresh, fruity, and floral white wines, including Pinot Gris/Pinot Grigio, Riesling, Gewürztraminer, Muscat, Colombard, Petit Manseng, and Chardonnay. White wines produced from botrytized grapes often contain elevated concentrations of 3-MHA. It is also an important component of many rosé wines and can enhance the fruity character of young red wines, occasionally contributing to blackcurrant notes.

3-Mercaptohexan-1-ol (3-MH), also known as 3-sulfanylhexan-1-ol (3-SH), is primarily associated with grapefruit and passion fruit aromas.

It is widely found in fresh, fruit-driven white wines and rosés, where it plays a significant role in enhancing aromatic intensity and freshness. Wines produced from botrytized grapes may contain particularly high levels of this compound.

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EUCALYPTOL Since the discovery of eucalyptol (1,8-cineole) in red wines by ETS Laboratories in 2003, we have detected and measured eucalyptol in a large variety of wines exhibiting “eucalyptus-like” aromas. Flavors perceived during tasting were usually strongly related to concentrations of eucalyptol. Regardless of the grape variety, trace levels close to 1 ppb are associated with “fresh”, slightly “minty” notes. In the low ppb range, “minty” or “fresh bayleaf” aromas become stronger, and more easily identifiable as “eucalyptus” as concentrations increase. Wines with strong “eucalyptus” odors may contain more than 20ppb of eucalyptol.

Eucalyptol’s sensory impact in wine is considered more or less desirable depending on the grape variety.

Wines from southern Rhône and Mediterranean varieties seem better able to accommodate the characteristic well. Moderate levels can be appreciated in wines from Bordeaux varieties. Whereas with Pinot Noir, even trace levels can detract from varietal expression.

Application: As eucalyptol may be mostly contributed by eucalyptus-derived MOG (leaves, bark debris…) hiding in grapes, analyzing grape samples before harvest is mostly pointless, and routine testing is not offered by ETS Laboratories.

Wine analysis assists winemaking teams in objectively documenting their sensory impressions and managing a strong flavor component. Unlike IBMP and smoke-derived Eucalyptol- Eucalyptus traits compounds (see p. 38), are considered typical in some “cult” wines; on the other hand, eucalyptol is relatively in excess, this character can slow to extract during be overwhelming. Even a slight red winemaking, making “eucalyptus” note can interfere shorter macerations a with delicate varietal aromas, and valid strategy to minimize can have a detrimental influence on certain grape varieties. impact.

Winemakers who wish to minimize or maintain consistent levels of “eucalyptus” character will also benefit by determining eucalyptol concentrations in distinct wine lots prior to blending.

IBMP Isobutylmethoxypyrazine (IBMP) is the most important methoxypyrazine, a group of molecules responsible for very distinctive vegetal aromas in Sauvignon Blanc and a variety of red wines, mainly from the Cabernet family. In Sauvignon Blanc, these compounds add an often desired “grassy” character.

In red wines however, the “green bell pepper” flavor is largely unpopular. Excessive IBMP levels lead to disappointing ratings and mixed success in the marketplace.

The “green bell pepper” flavor in wine depends primarily on IBMP levels in harvested grapes. Once grapes have been picked, IBMP levels are not easily altered by standard winemaking processes.

Application: The intensity of “green bell pepper/grassy” characters in wines can be predicted by measuring IBMP in grapes right before harvest. Grape screening of IBMP helps identify “problem” vineyards or blocks.

Since IBMP decreases during grape maturation, monitoring IBMP levels throughout ripening is a unique tool for assessing “aromatic maturity.” It allows targeting harvest dates based on desired aroma characteristics.

Monitoring IBMP from the early stages of the ripening process can greatly improve fruit quality from underperforming vineyards. Levels IBMP (2-Isobutyl-3in grapes are well known to be methoxypyrazine) is linked to vine vigor, canopy, and the main compound water availability, with severe responsible for the “green heat occasionally causing IBMP’s bell pepper” aroma in wine. natural degradation to stop. Once the kinetics of IBMP accumulation and degradation in specific sites are understood, viticultural practices can be modified accordingly. Once grapes have been picked, IBMP levels are not easily altered by standard winemaking processes.

The IBMP potential of grapes can be grossly underestimated from juice samples, making whole berries the preferred sample in most cases. However, analyzing juice samples may be relevant in white winemaking.

GLUTATHIONE Glutathione is not an aroma compound itself, but is a powerful antioxidant that protects white wines and rosés from oxidation and loss of aroma or flavor.

A low level of glutathione in grapes leads to lower levels in the juice and early losses of aroma compounds.

Glutathione levels fluctuate during production, as the compound can be absorbed by yeast and then released after fermentation.

If final glutathione levels are low in young wines, the wines will experience a faster loss of fresh varietal and fruity aromas, and poor aging potential.

Monitoring glutathione levels can be beneficial throughout the winemaking process to maximize white wine aroma and flavor, as well as prevent premature aging.

1 The glutathione content in grapes indicates their

antioxidant potential, and can be influenced by a number of factors including soil nitrogen, vineyard practices, and grape maturity levels.

2 Analyzing changes in glutathione levels during

production helps to pinpoint where in the process glutathione is being lost – often from contact with air or exposure to copper residues.

3 A testing program can also identify winemaking processes that boost glutathione release after fermentation, and increase levels in wines.

Glutathione, a natural grape antioxidant, can protect the aroma and flavor of white and rosé wines and prevents premature aging.

Note: Glutathione is extremely sensitive to contact with air. To help prevent oxidation of juice and wine glutathione samples, ETS provides complimentary sample tubes containing potassium metabisulfite for glutathione sampling.

WILDFIRE IMPACT WILD F IRE SMO K E IMPAC T O N WINE WAS I D E N T I FI E D A S A S E R I OUS P ROB L E M A FT E R T H E 2003 WILD F IRE S IN AU S TRA L IA A ND BRITI S H COLUM B I A . T H E CA L I FOR N I A WI N E I N D US T RY WAS A F F ECT E D DU E TO WIL DFIRES IN THE S UM M E R OF 2 0 0 8 , A N D S M OKE I M PACT H A S BE E N A CONCE RN FOR GROWERS A ND WINERI E S E VE R S I N CE . I T H A S B E E N R E P OR T E D T H AT W IL DF IRE I M PACT IN G RA PES A ND WINES IS CAUS E D BY A WI D E R A N GE OF VOL AT I L E P H E N OL S FO U ND IN WILD F IRE SMOK E. THES E CO MPO U ND S A R E A B S OR B E D A N D ACCUM UL AT E I N B E R R I ES. T HE Y EVE N T UALLY END U P IN WINE WHERE T H E Y CA N CAUS E UN WA N T E D FL AVOR S . T H E SE O F F F LAVORS, DES CRIBED A S “S MO K Y,” “B ACON ,” “ CA M P FI R E ,” A N D “A S H T R AY,” A R E U SUAL LY LONG LAST ING A ND L INGER O N THE PA L AT E E VE N A FT E R T H E WI N E I S S WA L LOWE D .

Sample Types for Analytical Testing During the 2008 California wildfires, ETS Laboratories developed an analytical tool to screen grapes for the risk of smoke impact. This analysis measured trace levels of free guaiacol and 4-methylguaiacol in whole berries. In 2021, two additional panels, with a larger number of volatile (free) smoke markers and one with glycosylated (bound) markers were launched. These additional indicators in berries add insight that can help winemakers assess their smoke exposure, and choose an appropriate course of action to mitigate the effects in their wines.

Vine exposure to wildfire smoke can vary widely within a small geographic area, depending on proximity to the fires and wind conditions. Obtaining representative samples can be challenging.

Mixing grape varieties in composite samples should be avoided, as grape cultivars often react differently to a similar exposure to smoke. Syrah grapes contain naturally occurring guaiacol and should never be mixed with grapes from other varieties prior to testing for wildfire smoke related compounds.

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Berries Smoke marker analysis on berry samples is usually required by crop insurance providers, although micro-ferment samples are becoming more widely accepted.

Submit 200 to 300 loose berries, keeping them cold and undamaged as much as possible (do not crush them). When shipping samples, use hard plastic containers with icepacks in an insulated package. Avoid submitting cluster samples when possible, to avoid additional fees, and delays in receiving results. It is advisable to keep backup samples in a freezer.

Juices It is possible to measure smoke exposure markers in juice samples, but the reported values may not represent the actual amounts of smoke compounds in the grape.

We strongly recommend against submitting juice samples for pre-harvest screening. The majority of smoke compounds are located in the skins. Crushing the grapes does not release all of the skin’s smoke related compounds into the juice.

For this reason, submitting whole berries for testing is preferred.

We do not accept fermenting samples, which may constitute a safety hazard.

G r a p e S a mp l e s

M i c r o - f e r m e nts

I m m e di at e

> 1 We ek

S e ns o r y Ev a l u at i o n

N ot v e r y u s e fu l

U s e fu l , b u t di f fi c u l t (ne e d fo r mu l t i p l e t r a i ne d t a s t e r s i nc l u di ng s e ns i t i v e i ndi v i du a l s )

Ana l y s i s Tu r na r o u nd Ti m e

1 - 3 day s

1 - 3 d ay s

Pr e d i c t i o n o f S m o k e ex p o s u r e i n Pr o du c t i o n Wi ne s

I ndi r e c t ( v a r i ab l e “ mu l t i p l i e r s ” b et w e e n g r a p e a nd w i ne results)

R e ds : m o r e di r e c t ( b u t d e l ay e d ) Whi t e s : u nc e r t a i n ( f e r m e nt w i t h s k i ns fo r “worst case s c e na r i o ” ? )

S a mp l e Pr e p a r at i o n Ti m e (b e fo r e s e nd i ng to t he l ab o r at o r y )

Figure 1: Grape Samples vs. Small Scale Ferments (Microferments) as pre-harvest testing options for wildfire smoke impact

Small Scale Fermentations (Micro-Ferments) Wines from small-scale fermentations (“micro-ferments” or “bucket ferments”) may be tested for volatile smoke markers (basic or extended panels) and for glycosylated markers to complement pre-harvest grape testing. The pros and cons of both tests are outlined in Figure 1.

Production Wines Analyzing production wines immediately after completion of primary fermentation allows a first assessment of wildfire impact. It is preferable to sample and analyze wines that have not come in contact with oak or oak-derived products which can contribute the same volatile compounds used as wildfire smoke markers.

It is still possible to get useful information for barreled wines from volatile smoke markers. Take samples from the most “neutral” barrels available and choose the extended panel of volatile (free) smoke markers rather than the basic volatile marker panel (guaiacols only). There is no issue analyzing oaked wines for glycosylated markers, since oak or oak products do not contain these compounds. Analyzing for glycosylated markers in wine is always relevant regardless of contact with oak.

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EXTENDED VOLATILE & GLYCOSYLATED MARKERS TH E EX TEN D ED VO L ATIL E (“F REE”) A ND GLYCOSYLATED (“BOUND”) MAR KE R PA N EL S , CUR R EN TLY O FFER ED BY ETS LA BORATORIES A ND THE AWRI, REPR E S E N T TH E M OST TECHN ICAL LY ADVA NC ED METHODS FOR DETERMINING W HE T HE R G R A PES O R WIN E HAV E B EEN A F F EC TED BY WILDF IRE SMOKE. THE EF F EC T I V E N E SS O F TH I S PAN EL I N DETECTI N G SMOKE IMPAC T IN GRA PES A ND WINES WAS ON C E AG A I N S UCCESSFUL LY D EMO NSTRATED DURING THE 2025 SEA SON.

WHAT L E V E LS AN D PAT T E RN S TO E XP EC T I N W I N E S? The following observations build on findings from previous vintages published in earlier editions of the Harvest Guide:

the absence of smoke exposure. Fortunately, baseline levels of the other volatile markers appear to remain within normal ranges, The most consistent trends we have seen is making them useful indicators of smoke that elevated volatile (“free”) smoke markers impact. are generally accompanied by elevated Petit Verdot is also an oddity, but in a different glycosylated (“bound”) markers. Figure 1 way. Although its baseline marker levels are illustrates this relationship in Cabernet normal, multi-year observations suggest Sauvignon wines, with levels ranging from that it is particularly sensitive to smoke normal baseline levels in non-smoke-exposed exposure, often accumulating substantially wines to extreme concentrations associated higher levels of smoke compounds than with severe smoke exposure. Similar patterns other varieties. Among the cultivars we have are typically observed across most red studied, Petit Verdot exhibits the widest range varieties, while white and rosé wines generally of smoke marker concentrations, with volatile show lower levels due to reduced skin contact guaiacol exceeding 200 µg/L and combined during winemaking. glycosylated markers approaching 1,000 µg/L. Syrah remains a notable exception. This Less frequently, we encounter samples with variety is known to contain naturally elevated relatively low volatile marker levels, but baseline levels of volatile guaiacol, even in elevated glycosylated markers. Examples 41

of this pattern are shown in Figure 2 (the three samples on the left). We observed this pattern in 2021 grapes and wines produced from California’s Sierra Foothills Rhône varieties. These cases are of concern because testing only for volatile markers would cause “false negative” results.

this response is specific to Pinot Noir remains unclear. One possible explanation is a reduced ability of the grapes to glycosylate smoke compounds, potentially linked to the severe heatwave that affected the western United States in August 2020, significantly reducing—or, in some cases, We have also observed the opposite pattern—high temporarily halting—grape metabolic activity. In volatile markers but relatively low glycosylated such cases, testing only for volatile markers would markers— particularly in some 2020 Pinot Noir be the cause of “false negative” results. wines (Figure 2, two samples on the right). Whether

Figure 1: Range of volatile and glycosylated markers observed in 2020 Cabernet Sauvignon wines, from normal baseline to extreme levels resulting from severe exposure to wildfire smoke.

Figure 2: 2020 white and red wines from various grape varieties (Whites: CH = Chardonnay, CB = Chenin Blanc, Rosé: GR = Grenache, Reds: PN = Pinot Noir) displaying atypical patterns between volatile and glycosylated smoke markers.

The three wines on the left have very low levels of volatile markers with high glycosylated markers, while the two wines on the right show opposite patterns.

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W HAT DID W E S E E FO LLO WI N G T H E 2 0 2 5 P I C K E T T F I R E? The 2025 Pickett Fire in Napa County exhibited notable differences compared to the 2020 Glass Fire.

The fire ignited on August 21, 2025 in the northeastern part of the Napa Valley. Prevailing southwesterly winds carried the smoke primarily eastward and northeastward. Early test results indicated that the smoke spared even vineyards located on the valley floor near the fire’s origin.

However, certain areas were heavily impacted.

Interestingly, in affected grapes and wines, the • smoke marker profiles differed from those observed in 2020 – see Fig. 3. These differences were mainly due to a higher relative abundance of syringoltype markers, as well as an overall increase in glycosylated forms. Two factors likely contributed to this pattern: •

Fire footprint and vegetation type: The Pickett Fire burned predominantly within the footprint of the 2020 Glass Fire, consuming extensive

areas of less-dense, regenerating vegetation rather than mature softwood trees such as Douglas fir. Softwood lignin is composed almost entirely of guaiacyl units and contains very few syringyl units, which explains why syringoltype markers were less abundant, sometimes even missing entirely, in 2020. In contrast, the vegetation burned in 2025 generated smoke richer in volatile syringols.

Timing within the growing season: The Pickett Fire occurred earlier in the growing season, when grapes were more metabolically active.

This likely led to increased glycosylation upon smoke exposure. Combined with the higher abundance of volatile syringols in the smoke, this explains why syringol gentiobioside—and, to a lesser extent, 4-methylsyringol gentiobioside— emerged as the primary analytical markers for this fire.

Figure 3: Volatile and glycosylated markers observed in 2020 Cabernet Sauvignon wines following the Glass Fire (three wines on the left) compared to 2025 Cabernet Sauvignon wines following the Pickett Fire (three samples on the right). Pickett Fire-impacted wines had more glycosylated markers overall, especially syringol and 4-methylguaiacol gentiobiosides

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Q&A WILDFIRE IMPACT

I WANT TO TEST GRAPES FOR SMOKE, WHAT can be mitigated to some degree by minimizing skin contact. With red grapes, a making rosé by the KIND OF SAMPLE SHOULD I BRING? The preferred sample for red or white grapes is a representative 200-300 loose berry sample, with berries as intact as possible. Transport in small rigid “sandwich boxes” works well – this is necessary if you are shipping samples. Avoid submitting cluster samples. Additional sample preparation time in the lab will delay results and there will be a processing fee. We do not recommend submitting juice samples.

SHOULD I CRUSH BERRIES AND LET THEM SOAK IN THEIR JUICE BEFORE BRINGING THEM? We do not recommend doing so. We must have consistent and uniform sample preparation for analyses to be comparable to baseline data concentrations. See pg. 47

direct pressing method can be a successful approach too. In case of significant maceration with skins (e.g. following machine harvesting or intentional skin contact) the risk level may be equivalent with both white and red grapes.

CAN I MIX BERRIES FROM DIFFERENT VARIETIES AND BRING A COMPOSITE SAMPLE? This is not advisable, and is not acceptable for samples submitted for insurance purposes. Over the years we have seen drastic differences in pick-up of smoke compounds between grape varieties. For example, Petit Verdot is often much more impacted than other Bordeaux cultivars. We have also seen substantial differences between Chardonnay and Pinot Noir.

WITH WHITE GRAPES, SHOULDN’T I BRING JUICE SAMPLES?

CAN YOU TEST FOR MORE THAN JUST “FREE” GUAIACOLS (GUAIACOL AND Since smoke compounds are mostly located in skins, 4-METHYLGUAIACOL)?

we still prefer whole berry samples for white grapes.

Our risk interpretation guidelines are similar for Yes, we offer a comprehensive extended volatile white and red grapes. Of course with white grapes, (free) and glycosylated (bound) markers panel. See the risk of smoke characters materializing in wine pages 41-42 44

CAN YOU TEST SYRAH GRAPES?

I’D LIKE TO HAVE MICROFERMENTS TESTED. Syrah naturally contains variable amounts of WILL ETS PREPARE THEM FOR ME? guaiacol, the main smoke marker. This makes it impossible to assess smoke impact based on guaiacol only, whether with grapes or micro-ferments. Now the extended volatile and glycosylated markers panel allows the assessment of Syrah samples.

We are not able to prepare or perform microfermentations for analytical testing. ETS recommends scanning the QR codes on the next page for micro-fermentation protocols from UC Davis, Washington State University and the AWRI.

Once fermentation is complete, transfer the fermented wine into a bottle, let settle in fridge for a few hours, decant and submit sample in a 60 mL Some laboratories offer testing after various acid and plastic tube. If you are considering an insurance heat treatments, in an attempt to measure “Total” or claim, check with your insurance provider for “Bound” forms in their entirety. We have serious and their policy guidelines and requirements regarding continuing reservations about such tests and do not smoke impact testing. offer them. Instead, for each of the volatile markers WILL YOU HELP ME WITH RESULTS listed in our extended panel, we measure directly by INTERPRETATION? HLPC/MS/MS its main glycosylated (sugar-bound) form (see figure 2). This is the strategy also adopted Yes, our experts are always available. Although each by the Australian Wine Research Institute (AWRI). fire event is unique, our interpretation guidelines based on volatile (free) guaiacol derived from our experience since 2008 have stood the test of time, WHEN IS THE BEST TIME TO BRING and have proven to be quite robust (Fig. 5). The SAMPLES? It is advisable to submit grape samples approximately extended volatile and glycosylated markers panel two weeks prior to harvest. Keep in mind that the allow refining and confirming diagnostics.

DOES ETS LABORATORIES MEASURE “TOTAL” MARKERS, OR ALL FORMS OF “BOUND” MARKERS?

impact of smoke is cumulative. “Negative” results early in the growing season may give a false sense of security, especially if there is more smoke exposure later on.

Figure 4: Glycosylated Smoke Markers and their isotopic analogues detected by LC/MS/MS (ETS Laboratories). These standards make quantitative, accurate and reproducible results (comparable over a long period of time and between different laboratories) possible.

WHAT ARE NORMAL “BASELINE” LEVELS FOR VOLATILE EXTENDED AND GLYCOSYLATED MARKERS? Grapes and wines naturally contain low “baseline” levels of smoke markers, variable by grape variety and possibly by geographic origin. While an online comparison tool is available from your client portal, the most accurate and valuable insights are always gained by developing your own baseline database for grapes, micro-ferments, and wines.

MY GRAPES (OR MICRO-FERMENTS) TESTED “POSITIVE.” SHOULD I HARVEST? Choosing whether or not to harvest or not will always be complex management risk decisions based on individual circumstances, with potentially painful consequences for both growers and wineries. Our interpretation guidelines are related to incremental risk. There is no “magic” number below which no risk is present and above which wines are guaranteed to be impacted.

WHAT IS YOUR TURNAROUND TIME? For the most accurate turnaround time log in to your client portal and view analysis details for the relevant panels.

In case of catastrophic and widespread fire events, we will keep our turnaround time information for grape, micro-ferment and wine tests prominently displayed and regularly updated.

A step-by-step procedure for small-scale fermentations (microferments) is available on the UC Davis Website: The AWRI protocol is found at:

The WSU Nano-Scale Fermentation Protocol:

INTERPRETATION GUIDELINES FOR WHOLE BERRY TESTS (EXCLUDING SYRAH): ANTICIPATED IMPACT IN WINE LOW

MODERATE 0.5

HIGH

VERY HIGH

1.0

2.0

FREE GUAIACOL (ug/kg)

GUIDELINES FOR MICROFERMENTS AND UNOAKED WINES (AGAIN EXCLUDING SYRAH): UNLIKELY 1.0

2.0

POSSIBLE 3.0

LIKELY 4.0

MOST LIKELY 6.0

FREE GUAIACOL (ug/L) Figure 5: Guidelines for volatile (free) guaiacol, the main marker of wildfire smoke impact, in grapes and micro-ferments and unoaked wines. Additional markers in the extended volatile panel as well as glycosylated markers allow refining and confirming assessments.

ALL SAMPLES SHOULD BE SHIPPED TO OUR ST. HELENA LOCATION:

ETS LABORATORIES 899 ADAMS ST. Ste. A St. Helena, CA 94574 46

SAMPLING

PROTOCOLS It’s important to collect and handle harvest samples carefully to ensure accurate and representative results. We’ve compiled our recommendations to help you get the most out of your harvest analyses.

JUICE SAMPLING Most harvest samples received at ETS Laboratories come to the laboratory as juice.

Berries pressed for a juice sample should be selected from at least 20-40 different clusters, and can be easily pressed by hand in their collection bag. Pour the juice into a standard ETS 60mL sample tube and label with your ETS client labels.

Samples should be kept cool to prevent fermentation.

BERRY SAMPLING Take 200-400 berries per block. Pick berries from random clusters on both sides of the row. Take berries from the top and bottom of both the front and back of each cluster. *Samples submitted for berry analysis should contain only intact and undamaged fruit.

GRAPE SAMPLING FOR PHENOLICS For grape phenolic testing, a representative sample is critical to obtain accurate results, especially in varietals with tight clusters. Samples for the Grape Phenolic Panel should include berries from at least 20-40 different clusters. Clusters can be collected either from LABELING harvest containers or directly from the vineyard.

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To get a representative sample, all the berries must be stripped from the clusters and mixed before bagging a 300-400 berry sample for analysis (about 500g or 16 oz).

Each bag of berries should be clearly labeled with the client name, sample ID, and analyses to be performed.

Samples should contain only intact and undamaged fruit to ensure accurate results.

ETS Laboratories provides free sample labels that are preprinted and barcoded with your client ID.

We encourage clients to submit berry samples rather than whole clusters. If samples are submitted as clusters, ETS Laboratories will prepare a berry sample for an additional fee.

Visit our website, or give us a call.

TIME TO ORDER HARVEST SUPPLIES Don’t get caught empty handed – order complimentary tubes, pre-printed labels, and shipping pods to take the headache out of collecting and shipping samples.

1. Login to your ETS account and select the winery you're ordering supplies for.

2. Use the "Get Supplies" button on the dashboard to place a supply order.

Outside the range of our sample pickup service?

ETS Laboratories offers free shipping kits, which include an insulated envelope and an ice pack, to help you easily send in samples no matter where you're located.

S H I PP IN G JU I CE S AM P LES FO R R EGU LAR AN ALYS ES To prevent problems from fermentation, juice samples should be frozen or boiled for shipment, and clearly marked as either “FROZEN” or “BOILED” depending on the treatment used.

Boiling Boil samples with a loosely fitting cap to prevent evaporation and concentration. Do not over-boil.

Freezing Freeze the sample in a plastic ETS sample tube. Do not over-fill the tube — leave a small space for the sample to expand when frozen.

Never freeze samples in glass containers to prevent breakage and injury.

S HI P P I N G JU I CE SAMP LES FOR S CORPION™ AN ALYS I S To ensure accurate results, it's important to avoid damaging DNA or killing yeast and bacteria: ° Keep samples cool with ice packs. ° Ship by overnight delivery using a parcel carrier like FedEx, UPS, or GLS. Scorpion™ samples should not be frozen or boiled.

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LOCATIONS

& SERVICES IN A D D I T I O N TO O U R S T H E L E N A H E A D QUA R T E R S, W E OP E R AT E LABO RATO RI E S AC ROSS T H E W E ST COA ST, P ROV I D I N G ADVANC E D AN ALY T I C A L TOO L S A N D E XP E R T SU P P O R T TO WIN E M AKE RS I N E AC H OF T H E M A JOR W I N E - GROW I N G R EGI ON S WE S E RVE .

THE S E Q U I C K G U I DE S P ROV I D E A R E F E R E N C E FO R T H E 2 0 2 6 HARV E S T, I N C LU DI N G W E E K E N D H O U R S A N D CO N V E N I E N T SER VI C E S TO M AKE I T E A SI E R T H A N E V E R TO SE N D I N HARV E S T S AM P LE S , I N C LU D I N G D RO P B OX LOC AT I O N S A N D COM P LI M E N TARY CO U R I E R SE R V I C E .

AS ALWAYS , I F YO U H AV E A N Y Q U E ST I O N S, JU ST C A L L A N D WE’ LL B E H APPY TO H E L P.

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S T. H E L E N A C A L I F O R N I A

PHONE

(707) 963-4806

SHIPPING ADDRESS

A F T E R H O U R S D RO P B OX S T. H E L E N A Located at our laboratory, next to the main entrance.

COURIER SERVICE Our complimentary courier service is available in Napa, Sonoma, and Mendocino counties every day ETS is open.

Samples left overnight will be processed when we open the following business day.

REQUEST A PICKUP

899 Adams Street, Suite A St. Helena, CA 94574

You can request a courier pickup by logging in to your ETS account, or by calling our lab.

SEE INSTRUCTIONS FOR SHIPPING JUICE S A M P L E S – P. 4 1 DEADLINE

Please request a pickup by 10 am

HOURS Every Harvest, ETS offers extended and weekend hours.

Our team is on-call to meet your needs.

Please check the ETS Website for our most up-to-date business hours.

This allows us to ensure speedy turnaround on time-critical harvest analyses.

DROPBOX IS LOCKED FO R T H E P I N C O D E , C A L L U S , O R LO G I N TO YO U R E T S A C C O U N T A N D V I S I T “ C O N TA C T ”

For the most up-to-date dropbox hours and pick up times please check our website: www.etslabs.com/contact.

LO D I D RO P B OX E S TAT E C R U S H TA S T I N G R O O M

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OPENING HOURS T H E D R O P B O X I S AVA I L A B L E W H E N E S TAT E C R U S H I S O P E N : ( 2 0 9 ) 3 6 8 - 7 5 9 5

To schedule on-call service, please call by 2pm on Friday: (707) 963-4806

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759 Technology Way Napa, CA 50

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PHONE

(805) 434-9322

CALIFORNIA

A F T E R H O U R S D RO P B OX PA S O R O B L E S Located at our laboratory, next to the front door.

ADDRESS

Samples left overnight will be processed when we open the following business day.

3320 Ramada Drive, Suite B Paso Robles, CA 93446

COURIER SERVICE Our complimentary courier service is available to our Central Coast clients every day ETS is open.

REQUEST A PICKUP

You can request a courier pickup by logging in to your ETS account, or by calling our Paso Robles lab.

DEADLINE

Please request a pickup by 10 am.

I F YO U N E E D TO S H I P S A M P L E S , P L E A S E S E N D T H E M D I R E C T LY T O O U R S T . H E L E N A LAB: 899 ADAMS STREET, SUITE A ST. HELENA, CA 94574

This allows us to ensure speedy turnaround on time-critical harvest analyses.

HOURS Every Harvest ETS offers extended and weekend hours.

Our team is on-call to meet your needs.

Please check the ETS Website for our most up-to-date business hours.

COURIER SERVICE SERVICE AREA DROPBOX IS LOCKED. FO R T H E P I N C O D E , C A L L U S , O R LO G I N TO YO U R E T S A C C O U N T A N D V I S I T “ C O N TA C T ”

D R O P B O X L O C AT I O N S S A N TA M A R I A 2330 Westgate Road Suite 9 Santa Maria, CA, 93455

LOMPOC 333 North D Street Lompoc, CA, 93436

B U E L LTO N To schedule on-call service, please call by 2pm on Friday: (707) 963-4806 51

90 Easy St, Buellton, CA 93427 FOR ALL CENTRAL COAST DROPBOXES, PLEASE D R O P S A M P L E S B Y 1 1 : 0 0 A M F O R S A M E - D AY D E L I V E R Y M O N D AY - F R I D AY

We're currently picking up samples in the Paso Robles and SLO areas. We will continue to expand as demand growsplease let us know if you'd like service.

HEALDSBURG CALIFORNIA

PHONE

D R O P B O X L O C AT I O N S

(707) 433-7051

A F T E R H O U R S D RO P B OX HEALDSBURG

ADDRESS 190 Foss Creek Circle, Suite G Healdsburg, CA 95448

Located at our laboratory, on the north side of the building.

Samples left overnight will be processed when we open the following business day.

Please check the ETS Website for our most up-to-date business hours.

Our complimentary courier service is available in Napa, Sonoma, and Mendocino counties every day ETS is open.

REQUEST A PICKUP

You can request a courier pickup by logging in to your ETS account, or by calling our lab.

DEADLINE

I F YO U N E E D TO S H I P S A M P L E S , P L E A S E S E N D T H E M D I R E C T LY T O O U R S T . H E L E N A LAB: 899 ADAMS STREET, SUITE A ST. HELENA, CA 94574

HOURS Every Harvest ETS offers extended and weekend hours.

Our team is on-call to meet your needs.

COURIER SERVICE

Please request a pickup by 10 am This allows us to ensure speedy turnaround on time-critical harvest analyses.

DROPBOX IS LOCKED. FO R T H E P I N C O D E , C A L L U S , O R LO G I N TO YO U R E T S A C C O U N T A N D V I S I T “ C O N TA C T ”

To schedule on-call service, please call by 2pm on Friday: (707) 963-4806 52

NEWBERG OREGON

PHONE

(503) 537-6245

A F T E R H O U R S D RO P B OX NEWBERG Located at our laboratory, next to the main entrance.

Samples left overnight will be processed when we open the following business day.

ADDRESS 214 W. Hancock Street Newberg, OR 97132 I F YO U N E E D TO S H I P S A M P L E S , P L E A S E S E N D T H E M D I R E C T LY T O O U R S T . H E L E N A LAB: 899 ADAMS STREET, SUITE A ST. HELENA, CA 94574

HOURS Every Harvest ETS offers extended and weekend hours.

Our team is on-call to meet your needs.

Please check the ETS Website for our most up-to-date business hours.

D R O P B O X I S L O C K E D . F O R T H E P I N C O D E , C A L L U S , O R L O G I N TO YO U R E T S A C C O U N T A N D V I S I T “ C O N TA C T ”

COURIER SERVICE Our complimentary courier service is available in Salem, McMinnville, Newberg, and the surrounding areas every day ETS is scheduled to be open.

To schedule on-call service, please call by 2pm on Friday: (707) 963-4806 53

REQUEST A PICKUP

DEADLINE

You can request a courier pickup by logging in to your ETS account, or by calling our lab.

Please request a pickup by 10 am This allows us to ensure speedy turnaround on timecritical harvest analyses.

WALLA WALLA WASHINGTON

PHONE

ADDRESS

(509) 524-5182

3020 E. Isaacs Ave. Walla Walla, WA 99362

HOURS Every Harvest ETS offers extended and weekend hours. Our team is on-call to meet your needs.

Please check the ETS Website for our most up-to-date business hours.

COURIER SERVICE

I F YO U N E E D TO S H I P S A M P L E S , P L E A S E S E N D T H E M D I R E C T LY T O O U R S T . H E L E N A L A B : 8 9 9 A D A M S STREET, SUITE A ST. HELENA, CA 94574

A F T E R H O U R S D RO P B OX WA L L A WA L L A Located at our laboratory, next to the main entrance.

Our complimentary courier service is available in Walla Walla and the surrounding areas every day ETS is scheduled to be open.

REQUEST A PICKUP

You can request a courier pickup by logging in to your ETS account, or by calling our lab.

Samples left overnight will be processed when we open the following business day.

DEADLINE

Please request a pickup by 10 am This allows us to ensure speedy turnaround on time-critical harvest analyses.

To schedule on-call service, please call by 2pm on Friday: (707) 963-4806

DROPBOX IS LOCKED. FO R T H E P I N C O D E , C A L L U S , O R LO G I N TO YO U R E T S A C C O U N T A N D V I S I T “ C O N TA C T ”

D R O P B O X L O C AT I O N S PROSSER W I N E M A K E R S LO F T

R E D M O U N TA I N CO O P E R W I N E CO.

357 Port Ave Prosser, WA

35306 N Sunset Rd. Benton City, WA

PICKUP TIME: 10:45 AM

PICKUP TIME: 11:30 AM

PLEASE DROP SAMPLES BY 10:30 A M F O R S A M E - D AY D E L I V E R Y M O N D AY - F R I D AY

PLEASE DROP SAMPLES BY 11 A M F O R S A M E - D AY D E L I V E R Y M O N D AY - F R I D AY

RICHLAND CENTRAL INDUSTRIAL SALES 2235 Henderson Loop Richland, WA PICKUP TIME: 12 PM

WOODINVILLE 14030 NE 145th St., Suite B Woodinville, WA PICKUP TIME: 1 PM PLEASE DROP SAMPLES BY 8 PM FOR OVERNIGHT SHIPMENT M O N D AY - T H U R S D AY

PLEASE DROP SAMPLES BY 11:30 A M F O R S A M E - D AY D E L I V E R Y M O N D AY - F R I D AY

W A PAT O H O P TO W N P I Z Z A 2560 Donald Wapato Rd. Wapato, WA PICKUP TIME: 10:00 AM PLEASE DROP SAMPLES BY 9 : 4 5 A M F O R S A M E - D AY D E L I V E R Y M O N D AY - F R I D AY

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