Measuring and Calculating Alcohol in Distilled Spirits and Liqueurs EMPHASIS ON CONTEMPORARY HIGH-EXTRACT CONTAINING SPIRITS
WRITTEN BY GARY SPEDDING, PH.D.
INTRODUCTION
to extracted botanicals or sometimes additions of small amounts of sugar and citric acid in the case of non-flavored vodka. In cases where distillation could Measuring traditional distilled spirits often required no more than simple be avoided it was noted that, to ensure true proof determinations, the effect laboratory-scale distillation and determination, using specific gravity or of dissolved solids on alcohol determinations needed to be accounted for. density measurements of alcohol, by weight and volume, from a known This method known as “proof obscuration testing” was described by agencies amount of the spirit. This is especially so for spirits containing only tiny such as the US TTB (formerly BATF). For those spirits containing amounts amounts of extract. For those containing below 400 milligrams/100 mL of of extract between 400-600 mg/100 mL an obscuration factor could be extract, direct density measurements could even be made using a device determined by drying down the spirit and using that factor to accurately known as a pycnometer (density bottle) and an analytical balance (no determine the true or real solids content. distillation needed). Thus these measurements generally allowed an accurate It was determined that 0.1 gram solids or extract/100 mL of spirit would determination of alcohol via the use of tabulated data of density (or specific hide (mask or obscure) 0.4 degrees of Proof of alcohol, in other words gravity) values vs. alcohol concentrations (weight and volume respectively) lowering the apparent proof by 0.4 ° proof. In the US Proof is defined as without the need to account for the trace of extract that might be present. twice the percent alcohol by volume content when expressed at 60 °F. From Later on hydrometers were adopted by distillers to determine gravity, density direct density measurements the “apparent proof” is determined (regarded or proof values in such spirits. Now more sophisticated density meters are as close enough to true proof when solids are below 400 mg/100 mL of often used or recommended. However, it has long been forgotten that alcohol spirit). For 400-600 mg solids/100 mL the true proof is the apparent proof values determined by distillation need to be corrected to account for the plus the obscuration proof. Over 600 mg solids/100 mL the true proof had to specific gravity of the actual sample (which is defined based on both alcohol be determined by distillation according to older methods and rules (detailed and often high sugar or extract content). This includes cream liqueurs which at www.ttb.gov – Section 30.32). contain both a high fat and high sugar content. These cream-based products pose even more difficulties in measurement based on the use of the total fat TEMPERATURE CONSIDERATIONS content in defined, though problematic, equations. Note: Recently the TTB released a guiding document TTB G: 2014-1 detailing the approval of alternative devices for the determination of the proof content of distilled spirits.
This review focuses upon some issues involved in measuring alcohol content mainly in non-cream based liqueurs and spirits, when the spirit extract content is very high and when the alcohol by weight value is needed for calorie content determinations. When calories are to be determined the correct alcohol by weight needs to be known along with an accurate measure of the extract content (of known composition) of the original non-distilled sample of spirit. Volumetric distillations for high extract spirits in the laboratory only report the true alcohol by volume, not the correct alcohol by weight. The opposite is true for gravimetric distillations. Both cases assume that no interfering substances also distill over. Many in the industry have lost sight of this need for appropriate corrections and many modern methods such as GC or HPLC analysis for alcohol content do not figure out applicable corrections for the needs of the distiller to report calories based on the true alcohol by weight values and, moreover, do not provide the extract value itself which is required not only for carbohydrate estimations but also in total calorie determinations. Moreover, there is often times misconception by some of those new to the industry that caloric content is only dependent upon the alcohol present – it is not.
EXTRACTS
Instruments are available today to measure the density of traditional spirits very accurately and to report (based on tabulated values or complex algorithms) alcohol content by weight and volume as expressed at 20°C. This temperature is generally accepted for alcohol measurements in most countries. In the US, though, the alcohol content at 60°F is sometimes needed and still technically required for determination of the true proof value. This causes unnecessary issues, especially as there is only a slight overall difference in the volume of alcohol between the two temperatures 20°C vs. 60°F (which is equal to 15.56°C), the value being lower at 60°F. Tables of specific gravity vs. alcohol by volume at 60°F are available though becoming more difficult to locate today and all measurements made on modern digital instruments are at 20°C. Note: As liquid volumes of water and alcohol expand with a rise in temperature there is a slightly higher value of alcohol by volume - ABV at 20°C vs. 60°F. The weight of alcohol does not, however, vary under such conditions. An issue not considered in detail here also applies to dilution of alcohol and needs to be mentioned briefly. When volumes of water and alcohol are initially mixed together, a rise in temperature and volumetric contraction of the resulting solution occurs such that the total volume is less than the sum volume additions by roughly 3%. When mixing or diluting spirits, therefore, the distiller needs to be aware of the solution temperature (has it stabilized?), together with the final volume of the resulting product. The addition of sugars, syrups and flavorings, with their weight and volume contributions, to create liqueurs, makes careful measurements necessary therefore, to ensure that correct values of alcohol and extract are obtained.
EXTRACT DETERMINATION
Extract, or solids content, for traditional whiskies, bourbon, gin, vodka and such are generally made up of mineral content (calcium and magnesium ions, After dealing with the issues of measurement at 20°C vs. 60°F there are etc.), and possibly tannins and sugars extracted from wood aging, in addition other more pressing concerns for alcohol measurement that rely on principles
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