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Changes in wine ethanol content due to evaporation from wine glasses David Wollan, Duc-Truc Pham, and Kerry L. Wilkinson J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.6b02691 • Publication Date (Web): 17 Sep 2016 Downloaded from http://pubs.acs.org on September 19, 2016

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Journal of Agricultural and Food Chemistry

Title: Changes in Wine Ethanol Content due to Evaporation from Wine Glasses and Implications for Sensory Analysis

Authors: David Wollan1,2, Duc-Truc Pham1 and Kerry Leigh Wilkinson1,*

Research Affiliations: 1

The University of Adelaide, School of Agriculture, Food and Wine, PMB 1, Glen Osmond, SA

5064, Australia and The Australian Research Council Training Centre for Innovative Wine Production. 2

Memstar Pty. Ltd., 712 Research Road, Nuriootpa SA 5355, Australia

* Corresponding author: Dr Kerry Wilkinson, facsimile + 61 8 8313 7116, email [email protected]

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Changes in Wine Ethanol Content due to Evaporation from

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Wine Glasses and Implications for Wine Sensory Analysis

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Abstract

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The relative proportion of water and ethanol present in alcoholic beverages can significantly

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influence the perception of wine sensory attributes. This study therefore investigated changes in

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wine ethanol concentration due to evaporation from wine glasses. The ethanol content of

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commercial wines exposed to ambient conditions whilst in wine glasses was monitored over time.

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No change in wine ethanol content was observed where glasses were covered with plastic lids, but

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where glasses were not covered, evaporation had a significant impact on wine ethanol content, with

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losses from 0.9 to 1.9% alcohol by volume observed for wines that received direct exposure to

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airflow for 2 hours. Evaporation also resulted in decreases in the concentration of some

13

fermentation volatiles (determined by gas chromatography-mass spectrometry) and a perceptible

14

change in wine aroma. The rate of ethanol loss was strongly influenced by exposure to airflow (i.e.

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from the laboratory air-conditioning unit), together with certain glass shape and wine parameters;

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glass headspace in particular). This is the first study to demonstrate the significant potential for

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ethanol evaporation from wine in wine glasses. Research findings have important implications for

18

the technical evaluation of wine sensory properties; in particular, informal sensory trials and wine

19

show judging, where the use of covers on wine glasses is not standard practice.

20 21 22

Key words: alcohol, aroma, ethanol, evaporation, sensory evaluation, wine, wine glasses

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Introduction

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Besides the aesthetic appeal of wine glasses, knowledgeable consumers believe the shape, size,

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weight, clarity and/or color of glasses can profoundly affect their appreciation of wine sensory

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properties.1 Not surprisingly, there is a well-established market for wine glasses which

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manufacturers promote as having been optimized for particular wine styles. Differences in glass

29

architecture can supposedly enhance the aroma intensity, flavor balance and texture of wine.2

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Certainly the shape and size of a wine glass are thought to influence the development of favorable

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changes to wine sensory properties, for example, the process of wine ‘breathing’ or ‘opening up’ in

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the glass.3 The Australian wine show system has come to recognize these effects and has

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progressively moved away from ISO XL5 tasting glasses, to larger glassware options from Riedel

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or other manufacturers.4

35 36

The literature comprises several studies and reviews that describe the key matrix constituents of

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alcoholic beverages, such as whiskey, sake, shochu and wine, together with their effects on the

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volatility of aroma compounds, and their sensory impact.5–11 The relative proportion of water and

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ethanol present in alcoholic beverages, and their interactions with other matrix components (e.g.

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sugars, acids and tannins) can also have significant effects on the behavior of volatile compounds

41

responsible for aroma and flavor, both in the liquid phase and the headspace.9,12,13 However,

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changes in ethanol concentration of wine exposed to air in wine glasses have not previously been

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investigated. There are reports on the partitioning of aroma compounds between the liquid phase

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and the headspace14,15 and in a subsequent study,16 Tsachaki and colleagues reported the effect of

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ethanol, temperature and headspace gas dilution on the mass transfer coefficients of a range of

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volatile aroma compounds. Contrary to the decrease in volatile concentrations that might be

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expected in the headspace above a water-ethanol solution (i.e. compared to water alone), the

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presence of ethanol actually promoted evaporation of volatiles. The authors attributed this to the

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‘Marangoni effect’ (also called ‘tears of wine’17), which involves evaporation of alcohol from a thin 3 ACS Paragon Plus Environment


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film on the inner surface of a wine glass. Presumably this resulted in a reduction in ethanol

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concentration, yet there was no obvious attempt to measure changes in alcohol content with time.16

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It is standard practice in formal sensory studies to cover wine glasses, especially if samples are not

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being assessed immediately.18 However the reason behind this recommendation is to maintain the

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equilibrium of volatiles in the headspace; there is no specific mention of the potential for alcohol

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evaporation. Importantly, any change in alcohol concentration that occurs over time in wine

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exposed to ambient conditions has relevance in its own right, besides the loss of aroma volatiles. It

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remains contentious, but some winemakers believe there exists an alcoholic sweet spot

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phenomenon, where relatively small changes in alcohol concentration can have a disproportionate

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effect on the perceived quality and style of a wine.19 Some authors dispute the ability of sensory

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panels to discriminate differences in alcohol concentration below 0.5% alcohol by volume

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(abv).20,21 Nevertheless, the belief and associated practices continue.

63 64

The phenomenon of alcohol evaporation from wine glasses could have the most profound

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consequences for wine show judging. The Australian wine show system has been a feature of wine

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production and promotion for almost 200 years and has often influenced the quality and style of

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Australian wines.22 In this regard, it is notably different to more formal sensory evaluations, as

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noted by Lawless and Heymann.18 While the Best Practice Recommendations for the conduct of

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Australian wine shows suggests tasting brackets for individual judges should be limited to 30

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samples,4 it is not unusual for brackets to be larger, and therefore, to take over an hour to judge.

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Given wines are poured prior to judging and remain exposed to air during this period, samples

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judged late in a bracket may have changed significantly. Clearly this is a very different situation to

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the more rigorous protocols of formal sensory evaluations, yet the phenomenon may introduce

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random results to the wine show award system with significant commercial consequences. As such,

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this study aimed to measure changes in wine ethanol concentration due to evaporation from wine 4 ACS Paragon Plus Environment

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glasses as a function of time; i.e. to determine to what extent ethanol evaporation occurs and the

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potential impact on wine sensory properties.

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Materials and Methods

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Chemicals. Sodium chloride was purchased from Sigma Aldrich (Castle Hill, NSW, Australia).

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Deuterated internal standards (d5-ethyl propanoate, d5-ethyl-2-methylpropanoate, d9-2-methylpropyl

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acetate, d5-ethyl butanoate, d5-ethyl-2-methylbutanoate, d5-ethyl-3-methylbutanoate, d5-3-

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methylbutyl acetate, d5-2-methylbutyl acetate, d13-hexanol, d5-ethyl hexanoate, d13-hexyl acetate,

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d3-2-phenylethanol, d5-ethyl octanoate, d3-2-phenylethyl acetate and d5-ethyl decanoate) were

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synthesized, as previously reported.23

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Ethanol evaporation trials

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A series of experiments were performed to investigate changes in the ethanol concentration of

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(commercial) wines in glasses exposed to ambient conditions over time. In the first trial, a 2014

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Cabernet Sauvignon wine was poured into ISO standard XL5 wine glasses (50 mL per glass) which

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were either: (i) immediately covered with plastic lids (hereafter referred to as ‘covered’ wines); or

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(ii) placed (without covers) on a laboratory bench in a position that (a) avoided direct exposure to

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airflow (from a ducted air conditioner vent in the ceiling; hereafter referred to as ‘uncovered A’) or

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(b) received direct exposure to air flow (hereafter referred to as ‘uncovered B’). The air flow at

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these positions, being < 5.0 and 30.5 L/s, was measured with an AccuBalance Plus Air Capture

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Hood (TSI, Shoreview MN, USA); with the airflow from the air conditioner vent being 221 L/s.

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Ambient temperature and humidity conditions were 23 ± 1 °C and 35 ± 5%, respectively. At regular

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intervals, being t = 0, 15, 30, 45, 60, 75, 90, 105, 120, 240 and 360 min (Table 1), the ethanol

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content and density of wines (two technical replicates per treatment per time point) were measured

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with an Alcolyzer (Anton Paar, Graz, Austria). Changes in mass were also determined, as the mass

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of two technical replicates (per treatment), measured repeatedly with an analytical balance 5 ACS Paragon Plus Environment


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(AUW220D, Shimadzu, Rydalmere, NSW, Australia), at each time point. Trial 2 involved two

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white table wines, two red table wines and two fortified wines (Table 2) being subjected to the same

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treatment conditions as in trial 1 (i.e. covered, and uncovered with and without exposure to direct

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airflow), with the ethanol content of wines (two technical replicates per treatment) determined

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before and after (i.e. at t = 0 and 120 min). In trial 3, the influence of wine volume and glass type

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was studied (Table 4). Wine (the 2014 Cabernet Sauvignon from trial 1) was poured into XL5,

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sparkling and Riedel (Ouverture Magnum, Kufstein, Austria) wine glasses (50 mL per glass), which

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were then subjected to treatment conditions as above; with an additional treatment comprising 100

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mL of wine in XL5 glasses, also included. The ethanol content of wines (two technical replicates

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per treatment) was again determined before and after (i.e. at t = 0 and 120 min). Wine glass shape

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parameters, i.e. glass height, internal wine diameter and opening diameter (Figure 1), were

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measured with calipers.

114 115

Sensory analysis

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A triangle test24 was conducted with a panel of 18 judges to establish whether or not evaporation

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(for t = 120 min, as per trial 1 above) resulted in a perceptible difference in wine aroma. Wines

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were presented in a balanced, randomized presentation order, comprising all possible configurations

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(i.e. AAB, ABA, BAA, BBA, BAB and ABB, where A denotes covered wine and B denotes

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uncovered B wine) an equal number of times. Wines (50 mL) were served at 22–24°C, in covered

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ISO tasting glasses with randomly assigned four-digit codes, and panelists were asked to smell each

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sample and to identify the sample which was different.

123 124

GC-MS analysis

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The concentration of a range of fermentation volatiles (esters and alcohols) were determined in

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covered and uncovered B wines, to determine the impact of evaporation (for t = 120 min, as per

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trial 1 above) on wine composition. Measurements were performed by Metabolomics Australia 6 ACS Paragon Plus Environment

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(Australian Wine Research Institute) using gas chromatography-mass spectroscopy (GC/MS)

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according to stable isotope dilution analysis (SIDA) methods reported previously.23 This

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publication describes the preparation of internal standards and method validation. The conditions

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for headspace sampling by solid phase micro-extraction (SPME) were as follows: wine (1 mL) was

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diluted with buffer solution (9 mL, pH 3.7) and saturated with sodium chloride (2 g), prior to the

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addition of internal standards. A polyacrylate SPME fiber was subsequently exposed to the sample

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headspace for 10 min, prior to desorption (splitless mode), at an injector temperature of 200 °C,

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onto an Agilent 7890A gas chromatograph equipped with a Gerstel MPS2 multi-purpose sampler,

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and coupled to an Agilent 5975C mass selective detector. Separation was achieved with a

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Phenomenex wax column (60 m x 0.25 mm i.d. x 0.25 µm film thickness), with helium (Ultra High

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Purity) as the carrier gas (in constant flow mode). The initial oven temperature was 35 °C (held for

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3 min), then increased to 220 °C (at 5 °C/min, held for 3 min). The mass spectrometer quadrupole

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temperature was 150 °C, the source was set at 230 °C and the transfer line was held at 250 °C.

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Positive ion electron impact spectra (at 70 eV) were recorded in selective ion monitoring (SIM)

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mode with a solvent delay of 5 min. Raw data from Agilent ChemStation software (v E.02.02.1431)

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were converted into MassHunter data files and processed using MassHunter Workstation Software

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for Quantitative Analysis (v B.04.00). Fermentation volatiles were identified by comparing mass

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spectral data with the NIST mass spectral database and subsequently quantified against their

146

corresponding isotopically labelled internal standard.

147 148

Data analysis

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Chemical data were analyzed by one- and/or two-way analysis of variance (ANOVA) using

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GenStat (15th Edition, VSN International Limited, Herts, UK). Mean comparisons were performed

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by least significant difference (LSD) multiple comparison test at P< 0.05.

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Results and Discussion

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Ambient conditions were measured during the evaporation trials, and while temperature and

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humidity remained constant, at 23 ± 1°C and 35 ± 5% respectively, the air flow at positions A and

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B differed considerably, being < 5.0 and 30.5 L/s, respectively. These measurements were

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calculated to correspond to air speeds of 0.01 and 0.08 m/s respectively, which tend towards the

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lower end of wind speeds previously reported for indoor workplaces, which ranged from 0.01 to

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1.80 m/s and averaged 0.3 m/s, based on anemometer measurements.25 Nonetheless, uncovered

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wine glasses were clearly exposed to different airflows at the two positions, A and B, used in the

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current study.

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Influence of evaporation on wine ethanol content, density and mass

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No significant changes were observed in the ethanol content, density or mass of covered wines

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throughout the 360 minute duration of trial 1 (Table 1). However, where wine glasses were not

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covered, evaporation resulted in statistically significant differences in ethanol content being

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observed within just 15 minutes. After 6 hours, the ethanol content of wine exposed to moderate

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airflow (i.e. uncovered A wine) had decreased by almost 1% abv; which corresponded to a slight

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increase in wine density, i.e. from 0.9948 to 0.9959 g/mL, and the loss of almost 1 g of total wine

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mass. Where evaporation was exacerbated by direct exposure to airflow for 6 hours (i.e. in the case

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of uncovered B wine), ethanol content decreased by 3.2% abv, i.e. from 15.1 to 11.9% abv. In this

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time, wine density increased from 0.9948 to 0.9994 g/mL, with a corresponding loss of almost 3.5 g

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(approximately 7%) of total wine mass.

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Similar results were obtained in trial 2, which involved monitoring changes in ethanol concentration

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of different wines over 2 hours (Table 2). The ethanol content of covered wines remained constant,

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while the concentration of ethanol in uncovered wines decreased by between 0.2 and 1.9% abv,

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depending on both exposure to air flow and wine type. The largest change in ethanol content was 8 ACS Paragon Plus Environment

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observed for the wine with the highest initial ethanol content, such that after two hours, the alcohol

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content of (uncovered B) fortified wine 2, a non-vintage Muscat, had decreased from 21.7 to 19.8%

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abv. However, with the exception of this example, the initial wine alcohol content did not seem to

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influence the extent of ethanol evaporation, with the remaining wines each losing similar quantities

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of ethanol, i.e. 0.2 to 0.4% abv for uncovered A wines and 0.9 to 1.2% abv for uncovered B wines.

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Certainly, red wine 2 and fortified wine 1, which both had relatively high initial ethanol

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concentrations, did not lose substantially higher amounts of ethanol, relative to the lighter-bodied

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white wines 1 and 2, which had the lowest initial ethanol concentrations.

188 189

Although changes in alcohol concentration were more pronounced for uncovered wines exposed to

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direct airflow (i.e. uncovered B wines), it still took almost 2 hours for wine alcohol content to

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decrease by approximately 1% abv. For consumers, evaporation is therefore unlikely to be of any

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concern, since in most consumer-related wine consumption scenarios, it would be uncommon for a

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glass of wine to be exposed to ambient conditions for such a long time. However, more importantly,

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there are a number of professional wine tasting scenarios in which this could conceivably occur,

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including wine show judging. It is possible that the consistency of wine evaluation could be

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significantly affected by changes in alcohol content arising from ethanol evaporation, particularly if

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it is accepted that relatively small changes in wine alcohol content can profoundly influence aroma

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volatile partitioning9 and/or wine quality and style.

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Variation in airflow/air speed within a given tasting area will exacerbate the evaporation rates

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experienced by different judges, in addition to the varying times taken by different judges to

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complete evaluation of a bracket of wines (especially large brackets, which can comprise more than

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30 samples). This could be substantially overcome by ensuring wines are presented to judges in

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covered wine glasses. Whereas standard practice for formal, controlled wine sensory evaluations

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require wine glasses to be covered,18 informal sensory trials may be undertaken under far less 9 ACS Paragon Plus Environment


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rigorous conditions. Where evaluations are conducted over an extended period of time to

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accommodate panelist availability, and where wine glasses are not covered, there is again potential

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for wine alcohol content to significantly change due to evaporation, such that the sensory properties

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of the wines being evaluated may differ significantly between the time they are poured and when

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they are eventually assessed.

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Influence of ethanol evaporation on wine aroma and the concentration of fermentation volatiles

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A triangle test24 was performed to establish whether or not there was a perceptible difference in the

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aromas of covered and uncovered wines, following exposure to ambient conditions for 120 min.

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Covered and uncovered B wines were presented to a panel of 18 judges, 13 of whom correctly

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identified the different sample, demonstrating evaporation had a significant impact on wine aroma

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(at the 99% confidence level). GC-MS analysis of samples was subsequently performed to

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determine the impact of evaporation on the concentration of a range of fermentation volatiles (Table

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3). Of the volatiles measured, most (i.e. 11 of 15) were found at significantly lower concentrations

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in uncovered B wine compared with covered wine; with losses ranging from 64% for ethyl

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octanoate, to 100% for 2-methylpropyl acetate and hexyl acetate (albeit the levels of these two

222

compounds were already quite low). In contrast, moderate losses of just 21 and 38% were observed

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for hexanol and ethyl decanoate respectively, while concentrations of 2-phenyl ethanol and 2-

224

phenylacetate were similar (i.e. varied by ≤ 10%). These results support the observations of

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Tsachaki and colleagues16 who investigated the dynamics of these interactions and noted some

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significant enhancement of overall mass transfer from liquid to gas phase (headspace) for various

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volatile constituents in ethanolic solutions compared to aqueous solutions. Notably, this effect

228

varied from compound to compound. Importantly, it should also be recognized that other wine

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volatiles (i.e. in addition to those measured) would similarly have evaporated. The combined

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evaporation of ethanol and volatile compounds explains the apparent difference observed in the

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aromas of covered and uncovered B wines. Given the previously reported dynamic interaction of 10 ACS Paragon Plus Environment

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ethanol solution concentration with volatile headspace concentration,15 the loss of ethanol from

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uncovered B wine could enhance this effect.

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Influence of glass shape and sample volume on the evaporation of ethanol from wine.

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Several previous studies have attempted to investigate the influence of glass shape on wine sensory

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properties. Glass shape (‘beaker’, ‘tulip’ vs. ‘bulbous’) was found to influence the hedonic ratings

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given by untrained panelists to white and red wine aroma;26 but no such effect was apparent when

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visual and tactile cues were removed.27 In contrast, a recent study found glass shape and/or

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equilibration time affected both wine headspace composition and the intensity of aroma sensory

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descriptors, albeit no correlations were found between various wine glass shape parameters and the

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intensity of wine aroma attributes.28

243 244

In the third evaporation trial, the influence of glass shape/size and sample volume (Figure 1, Table

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4) on the evaporation of ethanol from wine was investigated (Table 5). As expected, there was no

246

change in the ethanol concentration of covered wines; nor was a significant change observed when

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uncovered A wine volume was doubled to 100 mL (in the XL5 glass). Relatively small (i.e. ≤ 0.2%

248

abv), but statistically significant changes in wine ethanol content were observed for uncovered A

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wines in XL5 and sparkling wine glasses. In contrast, the ethanol concentration of uncovered A

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wine decreased substantially, i.e. by 0.7% abv, in the Riedel glass. The most significant changes in

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wine ethanol content occurred for uncovered B wines, which can be attributed to direct exposure of

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wine glasses to greater ambient airflow. The larger dimensions of Riedel glasses resulted in the

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greatest evaporation of ethanol, such that wine ethanol content decreased from 15.1 to 13.2% abv.

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This observation is consistent with wine evaporation results reported by Venturi and colleagues,29

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who found changes in wine volume loss due to evaporation (based on changes in weight of glass

256

content) was greatest for glassware with the largest opening diameters.

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In this study, the main parameters directly related to the shape and size of the glass were volume

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and opening diameter; both of which significantly influenced changes in wine ethanol concentration

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(Table 5). However, differences in ethanol concentrations were evident for XL5 wine glasses

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containing different volumes of wine. In this comparison, wine glass dimensions were identical and

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only wine volume, wine surface area, wine surface circumference, and glass headspace volume

263

differed; albeit surface areas were similar, being 31.7 and 33.2 cm2 (Table 4). This suggests that by

264

themselves, or together, glass volume and opening diameter did not explain the differences

265

observed. Correlation coefficients (R2) were therefore calculated for changes in wine ethanol

266

content vs. various wine glass dimensions (volume and opening diameter) and/or wine parameters

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(wine and headspace volumes, surface circumference and surface area) parameters (Table 6); with

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the strongest correlations (R2 values of 0.999 and 0.970) being observed for headspace volume and

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the ratio of headspace volume to wine surface area, for uncovered A and uncovered B wines,

270

respectively.

271 272

Headspace volume, calculated as the glass volume less the volume of wine sample, seemed to be

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strongly correlated with changes in ethanol concentration, particularly when other parameters, i.e.

274

wine volume, glass opening diameter, surface circumference and surface area, were considered

275

(Table 6). These correlations point to the influence of larger glass dimensions on the rate of ethanol

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evaporation. However, wine volume also needs to be taken into account; correlation coefficients of

277

0.990 and 0.940 were calculated for changes in wine ethanol content of uncovered A and uncovered

278

B wines respectively, vs. the ratio of headspace volume to wine volume (Table 6). Interestingly, the

279

larger Riedel style wine glass had the greatest headspace to wine volume ratio, so it is worth

280

considering whether its increasing use in wine shows may exacerbate the effects of ethanol

281

evaporation, particularly under conditions similar to those used in the current study.

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The ethanol concentration of (uncovered) wine was found to decrease significantly over time as a

284

consequence of evaporation; with the rate of ethanol loss being strongly influenced by exposure to

285

airflow, together with glass shape, headspace and wine volume. However, the evaporation of

286

ethanol was prevented by simply placing covers over wine glasses. These findings have important

287

implications for the technical evaluation of wine, since even by the conservative assessments made

288

in previous studies, small changes in alcohol content (i.e. ~1% abv) can significantly influence our

289

perception of wine sensory attributes. In some instances, e.g. sensory trials (including those

290

employed for ‘alcohol sweet-spotting’) and wine show judging where the use of covers on wine

291

glasses is not standard practice, there is therefore the potential for significant sample variation as a

292

consequence of evaporation. The extent to which evaporation occurs will be influenced by ambient

293

conditions (temperature and airflow, in particular) and the glassware used. Evaporation can also

294

result in the loss of wine volatile compounds and can have a marked impact on wine aroma.

295 296

ACKNOWLEDGEMENTS

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The authors thank Tony Robinson (Treasury Wine Estates) for his considered and constructive

298

comments.

299 300

FUNDING SOURCES

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This research was conducted by the Australian Research Council Industrial Transformations

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Training Centre for Innovative Wine Production (project number IC130100005).



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REFERENCES

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FIGURE CAPTIONS

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Figure 1. Dimensions of XL5, sparkling and Riedel wine glasses (± 1 mm).

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Table 1. Changes in ethanol concentration, density and mass of Cabernet Sauvignon wine in covered and uncovered wine glasses exposed to ambient conditions over time (from 0 to 360 min); with uncovered glasses positioned to either (A) avoid or (B) receive exposure to direct airflow. Massa (g) Ethanol Content (% abv) Density (g/mL) Time Point (min) covered uncovered A uncovered B covered uncovered A uncovered B covered uncovered A uncovered B 0 15.1 15.1 a 15.1 a 0.9948 0.9948 a 0.9948 a 0.000 0.000 a 0.000 a 15 15.0 15.0 b 14.9 b 0.9948 0.9948 a 0.9950 b 0.008 0.049 ab 0.237 b 30 15.0 15.0 b 14.7 c 0.9948 0.9949 b 0.9952 c 0.014 0.095 abc 0.412 c 0.9948 0.9949 b 0.9953 d 0.019 0.133 bcd 0.565 d 45 15.0 15.0 b 14.6 d 60 15.0 14.9 c 14.5 e 0.9948 0.9949 b 0.9955 e 0.024 0.182 bcde 0.702 e 75 15.0 14.9 c 14.3 f 0.9948 0.9949 b 0.9958 f 0.028 0.221 cde 0.825 f 90 15.0 14.9 c 14.2 g 0.9948 0.9950 c 0.9959 g 0.033 0.264 def 0.953 g 105 15.0 14.9 c 14.2 g 0.9948 0.9950 c 0.9960 h 0.038 0.310 ef 1.082 h 120 15.0 14.8 d 14.0 h 0.9948 0.9950 c 0.9963 i 0.043 0.353 f 1.237 i 240 15.0 14.6 e 13.0 i 0.9948 0.9954 d 0.9978 j 0.075 0.672 g 2.328 j 360 15.0 14.2 f 11.9 j 0.9948 0.9959 e 0.9994 k 0.105 0.986 h 3.452 k ns P ns < 0.001 < 0.001 ns < 0.001 < 0.001 < 0.001 < 0.001 LSD 0.030 (treatment); 0.057 (time point) 0.000042 (treatment); 0.00008 (time point) 0.068 (treatment); 0.131 (time point) Values are means of two replicate measurements (n=2). Standard errors were ≤ 0.07 and ≤ 0.0005 for ethanol and density, respectively. Values followed by different letters within columns are significantly different; ns = not significant. a reported as a decrease in mass relative to t = 0.

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Table 2. Changes in ethanol concentration of wines in covered and uncovered glasses exposed to ambient conditions over time (0 to 120 min); with uncovered glasses positioned to either (A) avoid or (B) receive exposure to direct airflow. Ethanol Content (% abv) Wine initial covered uncovered A (t = 0 min) (t = 120 min) (t = 120 min) white wine 1 2011 Sauvignon Blanc Semillon 12.6 a 12.6 a 12.4 b white wine 2 2013 Sauvignon Blanc 11.3 a 11.3 a 11.1 a red wine 1 2009 Cabernet Sauvignon Merlot 13.7 a 13.6 a 13.3 b red wine 2 2014 Cabernet Sauvignon 15.0 a 15.0 a 14.8 b fortified wine 1 non-vintage Apera 16.3 a 16.3 a 16.0 b fortified wine 2 non-vintage Muscat 21.7 a 21.7 a 21.4 b Values are means of two replicate measurements (n=2). Standard errors were ≤ 0.15. Values followed by different letters within rows are significantly different.

uncovered B (t = 120 min) 11.4 c 10.4 b 12.5 c 14.0 c 15.1 c 19.8 c

P

LSD

< 0.001 0.002 < 0.001 < 0.001 < 0.001 < 0.001

0.072 0.267 0.054 0.165 0.200 0.256

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Table 3. Concentrations (µg/L) of fermentation volatiles in covered and uncovered B wine following exposure to ambient conditions (for 120 min); with uncovered glasses positioned to receive exposure to direct airflow. Threshold23 (µg/L)

Concentration (µg/L) P covered uncovered B ethyl propanoate fruity 1,840 385 a 115 b 0.001 ethyl 2-methylpropanoate fruity 15 200 a 66 b < 0.001 2-methylpropyl acetate banana, fruity 1,600 13 nd – ethyl butanoate acid fruit 20 291 a 79 b 0.001 ethyl 2-methylbutanoate sweet fruit 1 56 a 16 b < 0.001 ethyl 3-methylbutanoate berry 3 66 a 19 b < 0.001 3-methylbutyl acetate banana 30 339 a 100 b < 0.001 2-methylbutyl acetate banana, fruity 1,600 183 a 46 b < 0.001 hexanol green, grass 4,000 3,693 a 2,923 b < 0.01 ethyl hexanoate green apple 5 46 a 15 b < 0.001 hexyl acetate sweet, perfume 670 3 nd – 2-phenylethanol roses 10,000 75,746 b 79,628 a < 0.01 ethyl octanoate sweet, soap 2 39 a 14 b 0.002 2-phenylacetate floral 250 33 a 30 b < 0.001 ethyl decanoate pleasant, soap 200 8 5 < 0.1 Values are means of two replicate measurements (n=2). Relative standard errors were ≤ 5%. nd = not detected Values followed by different letters within rows are significantly different. Volatile Compound

Descriptor23

21



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Table 4. Changes in ethanol concentration of wines in covered and uncovered glasses exposed to ambient conditions over time (0 to 120 min); with uncovered glasses positioned to either (A) avoid or (B) receive exposure to direct airflow. Ethanol Content (% abv) Wine Glass P initial covered uncovered A uncovered B (t = 0 min) (t = 120 min) (t = 120 min) (t = 120 min) XL5 (100 mL) 15.0 a 15.0 a 14.9 a 14.3 b 0.002 XL5 (50 mL) 15.0 a 15.0 a 14.8 b 14.0 c < 0.001 sparkling 15.0 a 15.0 a 14.9 b 13.9 c < 0.001 Riedel 15.1 a 15.0 a 14.4 b 13.2 c < 0.001 Values are means of two replicate measurements (n=2). Standard errors were ≤ 0.15. Values followed by different letters within rows are significantly different.

LSD 0.228 0.165 0.092 0.300

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Table 5. Parameters of XL5, sparkling and Riedel wine glasses. Glass Wine Wine Wine Headspace Headspace Headspace Headspace Glass Wine Headspace Opening Surface Surface Surface Volume: Volume: Volume: Volume: Wine Glass Volume Volume Volume Diameter Diameter Circumference Area Wine Opening Wine Wine (mL) (mL) (mL) (mm) (mm) (mm) (cm2) Volume Diameter Circumference Surface Area XL5 (100 mL) 215 100 115 44 65 204 31.7 3.30 3.75 0.81 4.97 XL5 (50 mL) 215 50 165 44 64 199 33.2 1.15 2.61 0.58 3.63 sparkling 155 50 110 46 51 160 20.4 2.10 2.31 0.66 5.14 Riedel 560 50 480 68 72 226 40.7 10.20 7.50 2.25 12.53 Values are means of two replicate measurements (n=2). Standard errors were ≤ 0.15. Values followed by different letters within rows are significantly different.

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Table 6. Correlations between changes in wine ethanol content and various wine glass dimensions and/or wine parameters. Correlation Coefficient (R2) uncovered A uncovered B Changes in wine ethanol content vs. glass volume 0.975 0.805 Changes in wine ethanol content vs. wine volume 0.165 0.382 Changes in wine ethanol content vs. headspace volume 0.999 0.884 Changes in wine ethanol content vs. glass opening diameter 0.960 0.913 Changes in wine ethanol content vs. wine surface circumference 0.570 0.259 Changes in wine ethanol content vs. wine surface area 0.624 0.308 Changes in wine ethanol content vs. headspace volume/wine volume 0.990 0.940 Changes in wine ethanol content vs. headspace volume/glass opening diameter 0.989 0.842 0.996 0.921 Changes in wine ethanol content vs. headspace volume/wine surface circumference Changes in wine ethanol content vs. headspace volume/wine surface area 0.968 0.970

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Figure 1.

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TOC Graphic.

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Changes in Wine Ethanol Content Due to ... - ACS Publications

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