Sensory discrimination of blended Scotch whiskies of different product categories

Samples of 40 blended Scotch whiskies were analysed in a conventional sensory profiling experiment employing 26 trained assessors, nosing using a consensus vocabulary. Whisky blends were classified into four product categories on the basis of labelling and retail price: Deluxe (11), standard (22), multiple retailer (4) and West Highland (3). From the analysis of variance (ANOVA), highly significant attributes for discrimination between blended whiskies were pungent, smoky/peaty, smooth, woody, vanilla, sulphury and rancid whereas catty and sour/acetic were non-discriminating attributes. Principal component analysis (PCA) explained 58% total variance in four significant components. A version of partial least squares was used to assess the discrimination power of attributes in characterising blend categories. Deluxe category was mainly perceived as fruity, buttery, malty and nutty, standard as oily, sulphury, rancid, grainy, smooth, soapy, vanilla, solventy and sweet, retailer as solventy, soapy and rancid, and West Highland as woody, smoky/peaty, spicy and medicinal. Standard category blends were dispersed across the product spaces by sharing similarities in characters with retailer and also, less extensively, with Deluxe blends.     

Analytical Strategies to Confirm the Generic Authenticity of Scotch Whisky

The authenticity of a specific brand of Scotch whisky may be confirmed by comparing analytical data for suspect samples with reference to analytical ranges for the genuine brand. Wider generic authenticity issues exist when a product purports to be Scotch whisky when it has not been produced in Scotland in accordance with the legal definition of Scotch whisky. When such cases reach litigation, courts may ask chemists to analyse suspect products and draw conclusions on authenticity. This paper presents analytical profiles generated from a survey of Malt, Grain and Blended Scotch whiskies and compares the results with whiskies of other origins and examples of a diverse range of suspect products purporting to be Scotch whisky. The concentrations and ratios of concentrations of the major volatile compounds (or congeners), particularly methanol, n‐propanol, isobutanol and 2‐ and 3‐methyl butanol, were found to be important factors in the authenticity decision‐making process. In addition, the absence of known Scotch whisky congeners, the presence of compounds known to be absent from genuine whisky and abnormal maturation congener profiles all contributed to the decision process. From this review of genuine analytical profiles, an experimental protocol for determining the authenticity of Scotch whisky is proposed.     

Formation of Clusters in Whiskies During the Maturation Process

Maturation provides whisky with a mild and smooth texture by removing the irritating alcoholic flavor. However, the precise mechanism by which the whisky flavor is improved through the maturation process remains unknown. In this study, we performed mesoscopic structural measurements—dynamic light scattering (DLS) and small‐angle X‐ray scattering (SAXS)—to elucidate the relationship between the liquid structure and flavor maturation of whiskies. Both techniques detected two scattering components corresponding to the clusters formed by the extractives from oak casks during maturation, which are not present in the new make (freshly distilled whisky). Analyzing the scattering profiles revealed that only the small clusters increase in concentration during maturation. It is concluded the small cluster component is crucial for obtaining flavorful whiskies, while the large cluster component, whose concentration is independent of the maturation time, is related to the alcoholic irritation of the whiskies, as demonstrated by the sonication test.     

Sensory and Chemical Analysis of ‘Shackleton's’ Mackinlay Scotch Whisky

Three cases of Mackinlay's Rare Highland Malt whisky were excavated from the ice under Sir Ernest Shackleton's 1907 expedition base camp hut at Cape Royds in Antarctica in January 2010. The majority of the bottles were in a pristine state of preservation and three were returned to Scotland in January 2011 for the first sensory and organoleptic analysis of a Scotch malt whisky distilled in the late 1890s. Sensory analysis and the higher alcohol and maturation congener profiles describe a lightly peated malt whisky matured in American white oak sherry or wine casks. Analysis of process related compounds together with combined gas chromatography (GC) mass spectrometry and GC‐olfactometry analysis of fermentation related congeners show a distinctly ‘modern’ style of malt whisky. While Scotch malt whisky at the end of the 19th century was generally regarded as heavily peated and harsh in character, Charles Mackinlay & Co. Distillers were producing a malt whisky with an altogether more subtle character at their Glen Mhor distillery near Inverness. The sensory and chemical analysis of this unique whisky artefact significantly changes our understanding of the quality and character of Scotch malt whisky produced by our distilling forefathers.     

Chemical composition analysis and authentication of whisky

Whisky (whiskey) is one of the most popular spirit‐based drinks made from malted or saccharified grains, which should mature for at least 3 years in wooden barrels. High popularity of products usually causes a potential risk of adulteration. Thus authenticity assessment is one of the key elements of food product marketing. Authentication of whisky is based on comparing the composition of this alcohol with other spirit drinks. The present review summarizes all information about the comparison of whisky and other alcoholic beverages, the identification of type of whisky or the assessment of its quality and finally the authentication of whisky. The article also presents the various techniques used for analyzing whisky, such as gas and liquid chromatography with different types of detectors (FID, AED, UV–Vis), electronic nose, atomic absorption spectroscopy and mass spectrometry. In some cases the application of chemometric methods is also described, namely PCA, DFA, LDA, ANOVA, SIMCA, PNN, k‐NN and CA, as well as preparation techniques such SPME or SPE. © 2014 Society of Chemical Industry     

Measurement of Thresholds for Reference Compounds for Sensory Profiling of Scotch Whisky†

Sensory profiling of Scotch whiskies, important for research and product analysis, requires training of assessors including the identification of important whisky aroma characters. Seventeen compounds were selected as potential reference standards for common whisky sensory characteristics. Nineteen assessors determined detection and recognition thresholds for each reference standard dissolved in 3 year old grain whisky at 23% (v/v) ethanol using both ascending dilution series and Latin square presentations. With the former, order effects and errors of habituation and anticipation were apparent. However, the Latin square presentation was satisfactory for threshold measurements in whisky, yielding good correlations and reproducibility, and enabling outliers to be reassessed independently. Slopes obtained from plotting probit against concentration for detection and recognition data, psychometric functions of aroma perception, varied between reference compounds and 90% recognition concentrations were obtained for each aroma standard. Sixteen of the compounds assessed were suitable for use as reference flavour standards for training of whisky assessors.     

Investigation into the use of carbon isotope ratios (13C/12C) of Scotch whisky congeners to establish brand authenticity using gas chromatography-combustion-isotope ratio mass spectrometry

Volatile congeners of whisky have been analysed by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). Acetaldehyde, ethyl acetate, n-propanol, isobutanol and amyl alcohol from a popular blended whisky have been separated using established GC conditions and their δ¹³C%. values determined. Eight samples of the whisky blend taken over the last 2 years of production have been analysed to allow the authentic range to be determined. A radar diagram has been used to graphically represent the δ¹³C%. data. This was used as a simple means of comparing the carbon isotope profiles of whiskies. Two other whisky samples were analysed and shown to differ from the whisky blend on the basis of the δ¹³C values.     

两种泥煤对威士忌品质的影响

目的 为丰富国内威士忌产品的种类。方法 以澳大利亚麦芽为主要原料,分别利用阿坝州泥煤和拉脱维亚泥煤烟熏麦芽制作麦芽汁,再用酿酒酵母酿造泥煤威士忌;并对比两种威士忌的感官特征、理化指标及香味成分。结果 阿坝州泥煤烟熏过的麦芽汁发酵后的出酒率(24.2±1.18%)显著高于(P＜0.05)拉脱维亚泥煤,感官品质也显著优于(P＜0.05)拉脱维亚泥煤威士忌,且水果香和花香突出。通过气相色谱与质谱联用技术(Gas chromatography-mass spectrometry,GC-MS)分析两种威士忌的香味成分,共检测到20种挥发性物质,包括5种醇、5种酸、6种酯及4种其他物质;阿坝州泥煤威士忌中乙酸乙酯和异戊醇占比显著高于(P＜0.05)拉脱维亚泥煤威士忌;拉脱维亚泥煤威士忌中酸类化合物较多,酒体欠协调。结论 综合分析得出阿坝州泥煤更适用于威士忌酿造;研究结果为国产泥煤的应用和威士忌产品个性化发展提供借鉴意义。     

Evaluation of a Brazilian Fuel Alcohol Yeast Strain for Scotch Whisky Fermentations

Traditionally, distilling companies in Scotland have employed a very limited number of yeast strains in the production of alcohol for Scotch whiskies. Recent changes such as the decline in availability of brewers' yeast as a secondary yeast strain and the availability of yeast in different formats (e.g., dried and cream yeast as alternatives to compressed yeast) have promoted interest in alternative Scotch whisky distilling yeasts. In previous work, we investigated different strains of yeasts, specifically Brazilian yeasts which had been isolated from and used in fuel alcohol distilleries. One of the Brazilian yeasts (CAT 1) showed a comparable fermentation performance and superior stress tolerance compared with a standard commercial Scotch whisky distilling yeast (M Type). The Brazilian CAT 1 yeast isolate was further assessed in laboratory scale fermentations and subsequent new make spirit was subjected to sensory analyses. The spirits produced using the Brazilian strain had acceptable flavour profiles and exhibited no sensory characteristics that were atypical of Scotch whisky new make spirit. This study highlights the potential of exploiting yeast biodiversity in traditional Scotch whisky distillery fermentation processes.     

Induction of Heme Oxygenase-1 by Whisky Congeners in Human Endothelial Cells

Abstract: It is expected that the production of the cytoprotective heme oxygenase-1 (HO-1) protein in endothelial cells would reduce severity of vascular injuries, while phenolic compounds are known to induce HO-1 mRNA and protein in various cells. We investigated the activation of HO-1 by whisky, which contains various phenolic substances. The congeners of whisky stored from 4 to 18 y in oak barrels were shown to induce an increase of HO-1 protein in human umbilical vein endothelial cells, while those of freshly distilled whisky spirit exhibited no activity. To determine the compounds with potent HO-1-inducing activity among the whisky congeners, several chemicals that had been reported to exist in whisky or oak barrels were screened, and coniferyl aldehyde and sinapyl aldehyde showed the activity. Thus, compounds that emerged in whisky during barrel storage induced cytoprotective protein, HO-1, in human endothelial cells.     

Origins of Flavour in Whiskies and a Revised Flavour Wheel: a Review

The nature and origins of flavour in whiskies are reviewed with the aim of developing a revised and simplified flavour wheel for training of sensory assessors. Scotch whiskies are perceived as having distinctive characters, generally recognised in pattern recognition (perception, macroscopic brain processing), rather than being subjected to a deconstruction process of evaluating attributes (sensation, microscopic brain processing). Although consumers use simple recognition judgements on whisky flavour in categorical assimilation, industry has a requirement for monitoring spirit quality that necessitates a more reductionist approach. Whisky flavour wheels identify attributes, specific components of flavour character, which can be demonstrated to sensory assessors using reference standards. The advent of cyclodextrin bound reference standards has enabled communication of information on flavour character in training of assessors, as exploited in the brewing industry. A revised flavour wheel, with characters illustrated by reference standards, is proposed to assist sensory training on attributes of whisky flavour character.     

Changes in wood extractives from oak cask staves through maturation of scotch malt whisky

Cask staves, prepared from American white oak, Quercus alba, were obtained from unused, new charred Bourbon, used Bourbon, first-fill Scotch and exhausted Scotch casks. The aim of the experiment was to determine the effect of repeated maturations of whisky on concentration and location of phenolic extractives in the cask wood. Contents of vanillic and syringic acids and the respective aldehydes, arising from hydrolysis of guaiacyl-syringyl lignin, and whisky lactones (cis- and trans-β-methyl-γ-octalactone), arising from charring, were determined. Staves were sampled at 5 mm intervals from the inner char surface to 25 mm depth and wood extracted with chloroform, heptane and aqueous ethanol. Contents of material absorbing at 520 nm, total phenols and vanillic and syringic acids, vanillin and syringaldehyde, were determined by high-performance liquid chromatography; both isomers of whisky lactone were quantified by high-resolution gas chromatography. New cask wood had a maximum for coloured material in the char layer, but maxima for other compounds at 5 mm below the char. As casks were reused in maturations of whiskies, the contents of aromatic aldehydes and acids were reduced in the first 20 mm of the wood and maxima for both acids and aldehydes shifted towards the centre of the staves. This suggested that repeated exposure to aqueous ethanol resulted in compositional changes in the lignin in the wood. The newly charred wood had a maximum for cis-β-methyl-γ-octalactone at 5 mm below the char and the trans isomer at 15 mm. In the first Bourbon maturation both isomers were largely depleted and with successive extractions the maxima moved into the cask until in the exhausted cask wood no lactone was detected.     

Addition of yogurt to wort for the production of spirits: Evaluation of the spirit aroma over a two-year period

Triggered by the development of lactic acid bacteria (LAB) during the production of Scotch whisky, this study examined the influence of yeast and LAB inoculation on whisky flavor. Four new spirits were produced using the same process. LAB were added as a form of a Greek yogurt's live culture. In each category (barley and rye), one sample was fermented with Greek yogurt while the other was fermented without it. The spirits were matured and analyzed at five different points. Results from gas chromatography-mass spectrometry (GC-MS) analysis showed basic volatile compounds, along with some important extra compounds with yogurt culture. The most obvious differences were observed in the concentration of butanoic acid, a characteristic acid in spirits undergoing lactic acid fermentation: to identify esters such as ethyl butanoate, ethyl isobutanoate, isoamyl butanoate, and 2-phenylethyl butanoate, they are not typical compounds in whisky.     

Influence of Zinc on Distiller's Yeast: Cellular Accumulation of Zinc and Impact on Spirit Congeners

Accumulation of zinc by a whisky distilling yeast strain of Saccharomyces cerevisiae was studied during fermentation of malt wort and synthetic defined medium. Zinc uptake by yeast cells was very rapid in malt wort, as zinc (0.32 μg/mL) was completely removed from the fermentation medium within one hour. The type of fermentable carbohydrate had an impact on the kinetics of zinc accumulation, with maltose most effective at enhancing metal uptake at zinc concentrations above 3.2 μg/mL. Enriching yeast cells with zinc by “preconditioning” impacted on the production of flavour congeners in the distillates produced from fermented cultures. Such distillates were characterised by an altered flavour and aroma profile. In particular, the production of some higher alcohols increased when yeast cells were preconditioned with zinc. This phenomenon is yeast strain related. Industrial fermentation processes, including brewing and distilling, may benefit from optimization of zinc bioavailability in yeast cultures resulting in more efficient fermentations and improved product quality.     

Detection of counterfeit scotch whisky by H and O stable isotope analysis

Neat Scottish whiskies and the local source water used for and during whisky production have been analysed for their ²H and ¹⁸O isotopic composition by High Temperature Conversion–Isotope Ratio Mass Spectrometry (TC/EA–IRMS). With coefficients of determination R² for δ²H and δ¹⁸O of 0.71 and 0.88, respectively, measured δ²H and δ¹⁸O values for water used in the production of Scottish whisky were found to be well correlated with the δ²H and δ¹⁸O values observed for the corresponding whiskies. By plotting bulk ²H against bulk ¹⁸O isotope abundance data of authentic whisky and counterfeit whisky samples it was possible to discriminate between samples of authentic whisky and samples of counterfeit whisky.     

Gas chromatography carbon isotope ratio mass spectrometry applied to the detection of neutral alcohol in Scotch whisky: an internal reference approach

Ethanol and the volatile congeners of Scotch whisky have been analysed by GC–combustion stable isotope ratio mass spectrometry (GC–C–IRMS). Ethanol, propan-1-ol, 2-methylpropan-1-ol and methylbutan-1-ol (2- and 3-methylbutan-1-ol) have been separated using gas chromatography and their ratios of stable isotopes of carbon (¹³C/¹²C) determined by combustion isotope ratio mass spectrometry. The internal isotopic correlations for the ethanol and the congeners from the same sample were determined. A close and reproducible correlation was found for ¹³C/¹²C ratios of propan-1-ol and ethanol in authentic whisky samples and is the basis for determining the addition of neutral alcohol to whisky. Initial studies suggest that the method has the ability to detect the addition of neutral alcohol, depending on the cereal source of the whisky and neutral alcohol concerned, without the need for reference to databases.     

Expression of 2 Lipomyces kononenkoaeα-Amylase Genes in Selected Whisky Yeast Strains

ABSTRACT: Nineteen whisky yeasts were evaluated according to their fermentation performance and ability to produce a palatable spirit. Four of these strains were selected and, together with a commercial wine yeast strain (control), were transformed with integration plasmids containing the LKA1 and LKA2 α -amylase genes from the yeast Lipomyces kononenkoae . Fermentation trials with starch-containing media indicated that the transformants produced between 47% and 66% of the theoretical ethanol yield. This study has resulted in progress toward the development of whisky yeast that could ultimately be used in a process during which production of amylases, hydrolysis of starch, and fermentation of resulting sugars to grain whisky occur in a single step.     

Differentiation of fresh and frozen/thawed fish, European sea bass (Dicentrarchus labrax), gilthead seabream (Sparus aurata), cod (Gadus morhua) and salmon (Salmo salar), using volatile compounds by SPME/GC/MS

BACKGROUND: A simple method based on solid phase microextraction/gas chromatography/mass spectrometry (SPME/GC/MS) was applied for studying the volatile profiles of whole fish samples of European sea bass (Dicentrarchus labrax) and gilthead seabream (Sparus aurata) and fillets of cod (Gadus morhua) and salmon (Salmo salar) during frozen storage in order to be able to differentiate a fresh product from one that has been frozen. Analysis of volatile compounds was performed on these two product types, fresh and after freezing/thawing following storage at ? 20 °C for 30 and 90 days. RESULTS: More than a hundred volatile compounds were found by SPME/GC/MS. Statistical processing by principal component analysis and ascending hierarchical classification was used to classify the samples into categories and verify the possibility of separating fresh samples from those that had been frozen and thawed. The compounds to be used as differentiators were identified. Four compounds were common to all species: dimethyl sulfide, 3‐methylbutanal, ethyl acetate and 2‐methylbutanal. Not only were they found in larger quantities after thawing but they also increased with the duration of storage at ? 20 °C. CONCLUSION: These four compounds can therefore be considered as potential markers of differentiation between a fresh product and one that has been frozen. Copyright © 2012 Society of Chemical Industry     

不同酵母对威士忌品质的影响

以大麦芽为原料,选用3种不同酵母（ACBC-1、ACBC-2及ACBC-3）发酵制备威士忌。比较不同酵母的发酵性能、理化指标及出酒率,采用气相色谱（GC）法测定威士忌挥发性香气物质,通过气味活度值（OAV）确定关键香气化合物并进行主成分分析（PCA）,并对制备的酒样进行感官评价。结果表明,酵母ACBC-1发酵性能最好,其发酵液的理化指标良好（总酸3.73 g/L,残糖3.00 g/100 g,酒精度6.42%vol,pH 4.1）,出酒率最高（70.78 mL/kg）。3个酒样共检出24种风味物质,其中醇类化合物为主,占77%～98%;OAV＞1的酯类化合物种类最多（5种）,其中乙酸苯乙酯、乙酸异戊酯及乙酸苯乙酯是关键香气物质,对酒样的香气贡献最大。3种酵母制备威士忌酒样感官评分顺序ACBC-1（90分）＞ACBC-2（76分）＞ACBC-3（71分）。结果表明,酵母ACBC-1适合酿造威士忌。     

Sensory flavour discrimination of Greek dry red wines

Aroma (16) and oral (17)—flavour by mouth, after‐taste and mouthfeel—attributes were separately profiled in 27 Greek red wines, products of single Greek indigenous grapes (Aghiorghitiko and Xinomavro) and international (Syrah and Cabernet Sauvignon) varieties and blends. From univariate analysis (ANOVA) of assessor data, 6 of 16 aroma and 16 of 17 oral attributes were significant (P < 0.05) in discriminations. Principal component analysis (PCA) product spaces of aroma and oral attributes explained 40% and 71% variance respectively. Discriminant partial least‐squares regression (DPLS), ANOVA and PCA discerned similar influences of variety and region of origin. Coding DPLS2 for variety, 76% and 38% of oral and aroma attribute variance respectively, and 39% and 18% category respectively were explained. Aghiorghitiko usage conferred fruity and sweet tastes and after‐tastes and smooth mouthfeel, typical of Peleponnese wines where this cultivar dominates. In contrast, Xinomavro products were bitter and sour in taste and bitter in after‐taste, with astringent and dry/dehydrating mouthfeel, but this was not characteristic of all wines from Macedonia. Copyright © 2003 Society of Chemical Industry