Wine & Viticulture Journal Summer 2022 Preview

Summer 2022 · Volume 37 Number 1

SUMMER

• Oxygen – friend and foe • Hidden micro-oxygenation in the winery • Tackling climate change – is the industry ‘all in this together’?

• Are grapes ripening faster?

• Tasting: Vermentino

CONTENTS

INDUSTRY ASSOCIATION COLUMNS 8

AGW (Tony Battaglene): Preparing for the reality of Vintage ‘22

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WINE AUSTRLIA (Liz Waters): Mapping the road to net zero emissions

10 ASVO (Brooke Howell): ASVO 2021 Awards for Excellence

WINEMAKING 12 RACHEL GORE: Oxygen - friend and foe 18 Hidden micro-oxygenation in the winery: are wine rackings impermeable to atmospheric O2?

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28 Taking control of fermentation: oxidative-reductive potential as a tool to manage fermentation 32 Sulfide-bound copper removal from red and white wine by depth filtration 30 AWRI REPORT: Better late than never: formation of distinctive pepper aromas in cool-climate Shiraz

CLIMATE CHANGE 38 Avoiding climate change: is the Australian wine industry ‘all

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in this together’?

VITICULTURE 44 Are grapes ripening faster or is early veraison leading to early maturity?

51 Effect of day and night temperatures on grape pigmentation 56 Kaolin: a sustainable techology to improve berry quality under a changing climatic scenario 62 Latest developments and potential uses of digital technologies and artificial intelligence to assess smoke

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contamination in grapevines, berries and taint in wines 64 ALTERNATIVE VARIETIES: Inzolia

BUSINESS & MARKETING 69 Wine consumer involvement: wine consumption history in brand management 71 Cellar doors thrive in 2020-21 despite - or possiibly with help from - COVID-19 73 How wine brands can effectively use social media

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VARIETAL REPORT 79 Vermentino

W I N E M A K I N G OX YG EN M A N AG EM ENT

Oxygen — friend and foe

By Rachel Gore, Director, Free Run Consulting Email: rgore@freerunconsulting.com.au

fatty acids and sterols needed to keep their cell wall transport mechanisms healthy. This assists them to cope with the stresses of fermentation, therefore limiting the amount of negative VSCs produced in the first place.

Oxygen also counteracts whatever amount of VSCs that may already be present by raising the redox potential of the wine.

It’s important to remember that all fermentations produce sulfur-based compounds and it is not possible, or desirable, to completely eliminate them from your winemaking. Rather, the goal is to try to limit the impact that the negative ones may have on your wine by utilising oxygen as a tool.

In addition to limiting the formation of these sulfur-based compounds, oxygen has the added benefit of stabilising colour in a red wine by reacting with the alcohol in the must to form aldehydes, which in turn react with anthocyanins (blue pigment) and tannins to form more stable molecules. Tannins are

Rachel walks readers through the effects of oxygen introduced during certain stages of the winemaking process and the various ways of controlling it.

Stay with me now — I won’t get too in-

also chemically changed through oxidative

depth with this, just reveal enough information

reactions and can evolve to become more

for us to move forward.

complex and rounded.

The term ‘redox potential’ refers to a

Oxygen exposure is a valuable and

wine’s state of balance between its level

readily available management option

of off-smelling sulfur-based compounds

throughout the winemaking process and

T

(excluding hydrogen sulfide) and the amount

many practical approaches are available

he role of oxygen in the winemaking

of available oxygen. When present, oxygen

to manage it. However, understanding the

process is extremely complex. It can

beneficially counteracts these compounds.

style requirements and market placement for

affect wine throughout the many stages

However, when a wine contains a higher

your wine is paramount when considering

of its production from the time the grapes are

amount of these negative sulfur-based

options and tools available for use during the

harvested up until it is consumed. Some of

compounds and not enough available oxygen

winemaking process.

the most significant effects can be observed

to mitigate all of them, then by definition you

during the early stages of harvest, pressing

have a reduced pool of oxygen from which

perceived as both positive and negative; low

and maceration, but it is relatively unclear how

these offensive sulfur-based compounds

concentrations of oxygen can exert positive

much exposure occurs and what is the full

could have been counteracted but weren’t.

effects while excess oxygen can adversely

effect on wine.

Such wine is now referred to as being

affect the quality of wine.

The process of oxidation can be

The influence of oxygen on grapes starts

‘reduced’. In addition to a wine’s aromas

as soon as berries are damaged or crushed.

being negatively affected by off-smelling

definition of two different strategies in the

In disease-free grapes, numerous oxidase

volatile sulfur compounds (VSCs), mouthfeel

management of the interactions between

enzymes are activated and start an oxidative

is also adversely impacted, aggravating the

oxygen and wine:

chain reaction. To understand a little more

perception of pH and tannin, making a wine

about the impact of oxygen, now might be a

appear disjointed and hard.

good time to take a brief look at the oxidation-

When oxygen is added to fermenting

reduction phenomenon called the ‘redox

must, it helps to limit the impact of negative

potential’.

VSCs by allowing yeast to synthesise the

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These opposing principles led to the

• total protection of wine from contact with air (hyper-reductive technologies) • the controlled oxygenation of wine (hyperoxygenation).

Both approaches are used in winemaking V37N1

V I T I C U LT U R E C L I M AT E C H A N G E

Are grapes ripening faster or is early veraison leading to early maturity?

By Wendy Cameron1*, Paul Petrie2, ‘Snow’ Barlow1, Cameron Patrick3 and Kate Howell1

IN BRIEF ■ Two reasons have been

suggested as to why some vintages in Australia have become compressed in recent years: grapes are ripening faster and advancing veraison.

■ Research set out to determine

Many growers in Australia have experienced an advancement in grape maturity timing over recent years. Researchers set out to determine if this trend was due to an advancement in the timing of veraison, using data from four different vineyards in Victoria between vintages 1999 and 2018.

INTRODUCTION As climate change progresses, vintages

the timing of veraison rather than an increased rate of ripening. To answer this question,

have been getting hotter and grape maturity

we used data from four geographically and

if advancement in the timing of veraison has led to compressed vintages.

has been occurring earlier across the globe

climatically different vineyards in Victoria, and

(Jones & Davis 2000, Petrie & Sadras 2008).

24 cultivars, over the vintage years between

In many Australian vineyards, the harvest

1999 and 2018. Using a statistical approach

■ Historical data from four

period has also been ‘compressed’ in some

with linear mixed effects models, we were able

recent seasons meaning it is happening over

to determine trends in the rate of ripening and

a shorter period of time (Petrie & Sadras

trends in veraison timing, which included the

2016). This puts strain on a wine business’

effect of yield, to investigate our hypothesis.

vineyards in Victoria located in different regions and with different climates were analysed across the 1999 and 2018 vintages.

■ Some evidence was found that

yield influenced the rate of ripening.

■ No significant change in the rate

of ripening was found; nor was there any evidence for a change in the length of time between veraison and maturity.

■ The advancement in maturity

timing was determined to be due to the advancement of veraison rather than an increase in the rate of ripening.

infrastructure to cope with more fruit being ready for harvest, but during a shorter time interval. Some winemakers and viticulturists

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The historical records of a commercial

have felt that one reason for this earlier

winegrowing business were used for this

maturity is that grapes are ripening faster.

study. Four vineyard locations were used:

Another explanation for the earlier maturity

Banksdale, Milawa, Heathcote and Mystic

is that veraison, the preceding phenological

Park. These represent a range of regions and

phase, has advanced. Yield has been

climatic parameters from across Victoria. The

implicated in grape ripening, veraison and

climate of these vineyards and the cultivars

maturity timing. Higher yields have been found

used in the analysis are briefly described in

to correspond to later maturity timing (Pearce

Table 1 (see page 46).

& Coombe 2004) and Parker et al. (2014)

Temperature data were obtained from

found that it was, in fact, the leaf area:fruit

Scientific Information for Land Owners

mass ratio that was a driver of veraison timing.

(SILO) (Jeffrey et al., 2001) using the nearest

We hypothesised that the advancement in maturity timing was due to advancement in

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METHODS

available coordinates to the four vineyard locations.

1 Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria 3010 South Australian Research and Development Institute, Waite Research Precinct, Urrbrae, South Australia 5064 3 Statistical Consulting Centre, University of Melbourne, Parkville, Victoria 3010 *Corresponding author: wtinson@student.unimelb.edu.au

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