Major constituents of fusel oils distilled from Australian grape wines

Fusel oils from Australian grape wines (Vine sp. Vitis vinifera) have been found to consist substantially of ethanol, n-propanol, isobutanol (2-methyl-1-propanol), isoamyl alcohol (3-methyl-1-butanol) and active amyl alcohol (2-methyl-1-butanol). In addition there are present large numbers of aliphatic esters, believed to be of considerable importance to grape brandy and spirit flavour and quality. The quantities and occurrence of these esters have been found to follow a systematic pattern. The major esterified alcohols are related to the free alcohols present and the major esterified acids occur as a series of acids of even carbon number with a maximum concentration at the n-decanoic acid. These relationships provide a basis for calculating the approximate ester composition of fusel oil.     

Quantitative determination of fusel alcohols in beer and fermenting wort

A simple quantitative method for determining four aliphatic fusel alcohols in beer and fermenting wort, namely n-propanol, isobutanol, 2-methyl-1-butanol and 3-methyl-1-butanol, has been developed. Samples were distilled at reduced pressure (10 Torr) and analysed by gas liquid-solid chromatography. Graphitised carbon black deactivated with 0.3% SP-1000 Carbowax 20 M modified with derivative of terephthalic acid and 0.3% phosphoric acid was used as column packing. Coefficients of variation determined were 3% or less. To serve as examples, contents of fusel alcohols in some commercial and experimental beers and a wort fermented for various lengths of time are reported.     

Major congeners of australian and imported brandies and other spirits as indicators of authenticity

The quantitative determination of the congeners methanol, n-propanol, ethyl acetate, i-butanol (2-methyl-1-propanol) and amyl alcohols (2-methyl-1-butanol and 3-methyl-1-butanol, which were not separated), was carried out on 61 Australian brandies, 61 French brandies and 50 wine distillates by gas chromatography. A comparison of the absolute amounts of congeners and their ratios (in the case of the C₃–C₅ alcohols) is presented in the light of several criteria of authenticity proposed by previous workers. Of these criteria, it was found that the amyl/i-butyl alcohol ratio and the i-butyl/n-propyl alcohol ratio were the most useful—on this basis, 11 French brandies (but no Australian brandy) were considered to be of suspect authenticity.     

Influence of nitrogen on the biological aging of sherry wine

Nitrogen compounds are essential to the growth and metabolism of yeasts. The uptake and metabolism of nitrogen compounds by Saccharomyces cerevisiae depend not only on the strain and its physiological condition, but also on the chemical and physical properties of its environment. The effect of the addition of different amino acids (L ‐proline, L ‐threonine, L ‐arginine, L ‐glutamic acid, L ‐leucine and L ‐valine) to nitrogen‐depleted natural or nitrogen‐free synthetic wine on the cell growth, flor velum formation and sherry wine compound production was investigated under controlled biological aging by S. cerevisiae var. capensis strain G1 a typical flor yeast. The formation of flor velum was dependent on particular amino acid, oxygen availability and the composition of wine. Consumption of glycerol was related with the cell growth; in contrast, acetaldehyde tended to be released. Amino acid supplementation resulted in the release to wine of amino acids, esters and higher alcohols. The amino acid which was released in nearly all cases was L ‐leucine. Addition of L ‐glutamic acid resulted in the release mainly of ethyl acetate, in the case of L ‐leucine isoamyl alcohols were released, and for L ‐valine isobutanol. In the three cases, 1,1‐diethoxyethane was released in large quantities. The findings might indicate that the regulation of metabolism succeeds in the most efficient balancing of the redox potential. Copyright © 2006 Society of Chemical Industry     

Contribution of wild yeasts to the formation of volatile compounds in inoculated wine fermentations

The aim of this work was to study the contribution of wild yeasts to the volatile composition of wine in inoculated fermentations. To do so, Parellada must, sterilized and inoculated with Saccharomyces cerevisiae strain Na33 (pure inoculated fermentation), inoculated Parellada must (mixed inoculated fermentation) and Parellada must that fermented with its wild yeasts (control fermentation) were used. From the results obtained in the pure inoculated fermentation it can be seen that S. cerevisiae produced appreciable quantities of isoamyl acetate, ethyl hexanoate, ethyl octanoate, and ethyl decanoate. However, the wild yeasts also contributed to the synthesis of esters since the total concentration of these substances was higher in the mixed inoculated fermentation than in the pure inoculated fermentation. 2-Phenylethyl acetate was only synthesized by wild yeasts when they did not compete with S. cerevisiae. The concentration of total alcohols was similar in the three samples; the important production of isobutanol and 2-phenylethanol in the control fermentation is noteworthy. As regards the acids, the greatest concentration corresponded to the mixed inoculated fermentation. The wild yeasts contributed to the synthesis of these compounds to a significant extent and S. cerevisiae synthesized appreciable amounts of short-chain fatty acids.     

Production and Characterization of Wine with Sugarcane Piece Immobilized Yeast Biocatalyst

In the present study, an economically cheap and sustainable food-grade yeast biocatalyst for wine production was successfully prepared. It was prepared through absorption technique by using fresh sugarcane (Saccharum officinarum L.) pieces as immobilizing support for yeast, Saccharomyces cerevisiae CFTRI 101. Immobilization was confirmed by scanning electron microscopy. Suitability of biocatalyst was investigated at low and room temperatures by using it in repeated batch. The fermentation rate and other parameters were compared with free yeast cells at different temperatures. In all cases, fermentation time was short (24 h at 30 °C and 98 h at 10 °C) and ethanol productivities were high as 4.2 g/l/h (3.33-fold at 30 °C and 2.31-fold at 10 °C). The volatile compounds methanol, ethyl acetate, propanol-1, isobutanol (2-methyl-1-propanol), and amyl alcohols (2-methyl-1-butanol and 3-methyl-1-butanol) that formed during fermentation were analyzed with the help of a gas chromatograph–flame ionization detector. The concentrations of ethyl acetate and methanol were not more than 100 mg/l in all cases, indicating an improvement in the product quality. Cell metabolism of immobilized yeast was not negatively affected by immobilization process. It was found that the immobilization of yeast cells on sugar pieces increased the fermentation rate and viability of yeast cells. Preliminary sensory tests recognized the fruity aroma, fine taste, and the overall improved quality of the produced wines.     

Killer strains of Saccharomyces: application for apple wine production

The aim of this study was to evaluate possible application of killer strains Saccharomyces paradoxus CBS 3702 (K1), S. cerevisiae CBS 6505 (K2) and S. capensis CBS 7903 (K3) for apple wine production. Apple musts were obtained from Jonagold apples. The optimal pH value of killer toxins activity, the temperature of their formation and the spectrum of activity against selected wine spoilage fungal strains were analysed. The influence of yeast strains on the chemical composition, volatile profile and sensory properties of apple wines was determined using high‐performance liquid chromatography and gas chromatography methods. The pH values of 4.2 (K1, K3) and 4.6 (K2), and a temperature of 28 °C, were optimal for the action of toxins. The analysed killer strains inhibited growth of seven of the 11 tested wine spoilage fungal strains. The samples obtained using the S. cerevisiae killer strain were characterized by the highest fermentation rate, highest ethanol concentration and a balanced level of volatiles, but their taste was described as bitter. S. capensis gained the highest scores in the sensory evaluation. It could be used for semi‐sweet or semi‐dry cider production, because of the lower amounts of ethanol formation but higher synthesis of glycerol, volatile esters and higher alcohols. Copyright © 2016 The Institute of Brewing & Distilling     

Gas-chromatographic determination of volatile constituents in Yugoslav plum brandies

Gas-chromatographic analysis, extraction and titration methods were used to determine the volatile components of 17 home-made natural plum brandy samples as well as 14 samples of industrially-produced plum brandy. The plum used for the production of Yugoslav plum brandies is Prunus domestica L. Eighteen alcohols, 23 esters and 21 organic acids were determined qualitatively and quantitatively. Eight aldehydes and nine ketones were only qualitatively determined. Apart from other components, the plum brandies analysed contained approximately 0.30 to 4.39 g of methanol/1; 0.40 g of 1-propanol/1; 0.19 g of 2-methyl-1-propanol/1; 0.05 g of 1-butanol/1; 0.10 g of 2-methyl-1-butanol/1; and 0.28 g of 3-methyl-1-butanol/1. The plum brandies also contained approximately 0.50 g of ethyl acetate/1 and about 0.03 g of acetaldehyde/1. The concentration of the free carboxylic acids present was about 1.50 g/1. Acetic acid constituted about 90% v/v of the total acid concentration.     

Effects of time of grape pomace fermentation and distillation cuts on the chemical composition of grape marcs

 The effects of fermentation time and distillation cuts on the composition of distillates in terms of ethanal, 1,1-diethoxyethane, methanol, 1-butanol, 2-butanol, 1-propanol, 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, ethyl acetate, ethyl 2-hydroxypropanoate, 3-methylbutyl acetate, hexyl acetate, 2-phenylethyl acetate, hexanol, trans-2-hexenol, trans-3-hexenol, cis-3-hexenol, 2-phenylethanol, ethyl butyrate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, ethyl dodecanoate, 2-methylpropanoic acid, 3-methylbutanoic acid, hexanoic acid, octanoic acid, decanoic acid, and dodecanoic acid were assessed through data generated according to a factorial design using analysis of variance and principal component analysis. Four times of storage of pomace obtained following winemaking of two grape varieties of white Verde wine (Alvarinho and Loureiro) and three distillation cuts were considered; volatile compounds in the 24 samples generated were analyzed directly, and indirectly after extraction and concentration, by capillary gas chromatography. The results generated have suggested clear differences (P<0.05) between distillate cuts obtained throughout fermentation times for each grape variety. The major differences between the different distillate fractions analyzed were accounted for by the contents of diethyl butanoate, ethyl 2-hydroxypropanoate, and the sum of 3-methylbutanoic and 2-methylpropanoic acids for Loureiro, whereas the main differences were accounted for by the contents of diethyl butanoate and the sum of the carboxylic acids for Alvarinho.     

Determination of the 13C/12C ratios of ethanol and higher alcohols in wine by GC-C-IRMS analysis

More than 50 authentic EU data bank wines from Germany (vintages: 2003, 2004 and 2006) have been extracted by liquid–liquid extraction with a mixture of cyclohexane and 2-methyl-2-propanol. The δ¹³C values of the extracted wine ethanol and other co-extracted higher alcohols have been determined by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). The stable isotope ratios of wine ethanol obtained by liquid–liquid extraction were compared with those obtained after distillation according to the official EU method. No significant differences of the isotope ratios of ethanol measured by the two compared methods were found (R ² = 0.972), thus it was concluded that no significant isotope effect during sample preparation occurred. Additionally, the ¹³C/¹²C isotope ratios of the major co-extracted alcohols, e.g. 2-methylpropan-1-ol, 2- and 3-methylbutan-1-ol, butan-2,3-diol and 2-phenyl-1-ethanol were determined and set in relation to the δ¹³C values of the corresponding extracted wine ethanol. Also, high correlations between their isotope ratios (e.g. 2,3-methylbutan-1-ol R ² = 0.829) were found. The key benefits of the introduced liquid–liquid extraction are the time- and cost-saving determination of δ¹³C values of wine ethanol, the small amount of sample needed for the extraction and additionally the potential analysis of the co-extracted higher alcohols which could be valuable for the detection of fraud.     

Determination of Three Alcohols in Chinese Dukang Base Liquor by FT-NIR Spectroscopy

Alcohols are important aroma compounds in Chinese liquors. In this work, 3-methyl-1-butanol, 1-butanol, and 1-propanol in Dukang base liquor were simultaneously analyzed by gas chromatography (GC) and fourier-transform near-infrared (FT-NIR) spectroscopy. The optimal combinations of spectral intervals for three alcohols were selected for modeling. The calibration models, which are based on FT-NIR spectral variables and the chemical values, were established with partial least square (PLS) and validated using internal cross validation. In calibration set, the coefficients of determination (R ²) for 1-propanol, 1-butanol, and 3-methyl-1-butanol were 95.21, 98.05, and 98.05, respectively; corresponding root mean square errors of calibration (RMSEC) were 0.27, 0.49, and 0.67 mg per 100 mL. In validation set, the R ² were 94.72, 97.96, and 95.22; the root mean square errors of prediction (RMSEP) were 0.40, 0.81, and 1.35 mg per 100 mL. The results indicated that the correlation between the values determined by GC and the values estimated by the calibration for the three alcohols was excellent. The FT-NIR spectroscopy calibration models, which with good prediction performance and high precision, could be used as a rapid methods for determination of alcohols in Chinese liquor.     

Fermentative behavior of Saccharomyces strains during microvinification of raspberry juice (Rubus idaeus L.)

Sixteen different strains of Saccharomyces cerevisiae and Saccharomyces bayanus were evaluated in the production of raspberry fruit wine. Raspberry juice sugar concentrations were adjusted to 16°Brix with a sucrose solution, and batch fermentations were performed at 22 °C. Various kinetic parameters, such as the conversion factors of the substrates into ethanol (Y_p/s), biomass (Y_x/s), glycerol (Y_g/s) and acetic acid (Y_ac/s), the volumetric productivity of ethanol (Q_p), the biomass productivity (P_x), and the fermentation efficiency (E_f) were calculated. Volatile compounds (alcohols, ethyl esters, acetates of higher alcohols and volatile fatty acids) were determined by gas chromatography (GC-FID). The highest values for the E_f, Y_p/s, Y_g/s, and Y_x/s parameters were obtained when strains commonly used in the fuel ethanol industry (S. cerevisiae PE-2, BG, SA, CAT-1, and VR-1) were used to ferment raspberry juice. S. cerevisiae strain UFLA FW 15, isolated from fruit, displayed similar results. Twenty-one volatile compounds were identified in raspberry wines. The highest concentrations of total volatile compounds were found in wines produced with S. cerevisiae strains UFLA FW 15 (87,435 μg/L), CAT-1 (80,317.01 μg/L), VR-1 (67,573.99 μg/L) and S. bayanus CBS 1505 (71,660.32 μg/L). The highest concentrations of ethyl esters were 454.33 μg/L, 440.33 μg/L and 438 μg/L for S. cerevisiae strains UFLA FW 15, VR-1 and BG, respectively. Similar to concentrations of ethyl esters, the highest concentrations of acetates (1927.67 μg/L) and higher alcohols (83,996.33 μg/L) were produced in raspberry wine from S. cerevisiae UFLA FW 15. The maximum concentration of volatile fatty acids was found in raspberry wine produced by S. cerevisiae strain VR-1. We conclude that S. cerevisiae strain UFLA FW 15 fermented raspberry juice and produced a fruit wine with low concentrations of acids and high concentrations of acetates, higher alcohols and ethyl esters.     

柿子果酒香气成分的GC-MS分析

利用气相色谱-质谱联用技术,对柿子果酒中的香气成分进行分析。通过分析固相微萃取法的萃取温度、萃取时间、萃取添加NaCl的量对测得柿子酒香气成分色谱峰的面积和数目的影响,优选出固相微萃取的最佳萃取条件为：萃取温度为50℃,萃取时间为40min,NaCl添加量为0.3g/mL（饱和）。比较固相微萃取、液-液萃取、蒸馏萃取这几种萃取方法,通过有效性验证,选出测定柿子果酒的最佳萃取方法是固相微萃取法。利用本实验优选的条件对柿子酒的香味物质进行萃取,共提取香气成分种类为55种,其中酯类23种,醇类15种,酸类13种,其他香气成分4种。柿子果酒的主要挥发性芳香成分是：异戊醇、苯乙醇、2-甲基-1-丁醇、甲酸异戊酯及异丁醇。     

Effects of time of grape pomace fermentation and distillation cuts on the chemical composition of grape marcs

 The effects of fermentation time and distillation cuts on the composition of distillates in terms of ethanal, 1,1-diethoxyethane, methanol, 1-butanol, 2-butanol, 1-propanol, 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, ethyl acetate, ethyl 2-hydroxypropanoate, 3-methylbutyl acetate, hexyl acetate, 2-phenylethyl acetate, hexanol, trans-2-hexenol, trans-3-hexenol, cis-3-hexenol, 2-phenylethanol, ethyl butyrate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, ethyl dodecanoate, 2-methylpropanoic acid, 3-methylbutanoic acid, hexanoic acid, octanoic acid, decanoic acid, and dodecanoic acid were assessed through data generated according to a factorial design using analysis of variance and principal component analysis. Four times of storage of pomace obtained following winemaking of two grape varieties of white Verde wine (Alvarinho and Loureiro) and three distillation cuts were considered; volatile compounds in the 24 samples generated were analyzed directly, and indirectly after extraction and concentration, by capillary gas chromatography. The results generated have suggested clear differences (P<0.05) between distillate cuts obtained throughout fermentation times for each grape variety. The major differences between the different distillate fractions analyzed were accounted for by the contents of diethyl butanoate, ethyl 2-hydroxypropanoate, and the sum of 3-methylbutanoic and 2-methylpropanoic acids for Loureiro, whereas the main differences were accounted for by the contents of diethyl butanoate and the sum of the carboxylic acids for Alvarinho. Received: 23 January 1998 / Revised version: 5 June 1998     

Comparative study of the biochemical changes and volatile compound formations during the production of novel whey-based kefir beverages and traditional milk kefir

Cheese whey (CW) and deproteinised cheese whey (DCW) were investigated for their suitability as novel substrates for the production of kefir-like beverages. Lactose consumption, ethanol production, as well as organic acids and volatile compounds formation, were determined during CW and DCW fermentation by kefir grains and compared with values obtained during the production of traditional milk kefir. The results showed that kefir grains were able to utilise lactose from CW and DCW and produce similar amounts of ethanol (7.8–8.3 g/l), lactic acid (5.0 g/l) and acetic acid (0.7 g/l) to those obtained during milk fermentation. In addition, the concentration of higher alcohols (2-methyl-1-butanol, 3-methyl-1-butanol, 1-hexanol, 2-methyl-1-propanol, and 1-propanol), ester (ethyl acetate) and aldehyde (acetaldehyde) in cheese whey-based kefir and milk kefir beverages were also produced in similar amounts. Cheese whey and deproteinised cheese whey may therefore serve as substrates for the production of kefir-like beverages similar to milk kefir.     

Characterisation of volatile compounds in an alcoholic beverage produced by whey fermentation

An alcoholic beverage (35.4% v/v ethanol) was produced by distillation of the fermented broth obtained by continuous whey fermentation with a lactose-fermenting yeast Kluyveromyces marxianus. Forty volatile compounds were identified in this drink by gas chromatography. Higher alcohols were the most abundant group of volatile compounds present, with isoamyl, isobutyl, 1-propanol, and isopentyl alcohols being found in highest quantities (887, 542, 266, and 176 mg/l, respectively). Ethyl acetate had the highest concentration (138 mg/l) among the esters. Besides higher alcohols and esters, other components, including aldehydes, acids and terpenes were also identified in the whey spirit. Considering that the quality of an alcoholic beverage can be evaluated by the relation between isoamyl alcohol/2-methyl-1-propanol and 2-methyl-1-propanol/1-propanol, which have to be higher than unity, it was concluded that a novel spirit of acceptable organoleptic characteristics can be produced by cheese whey continuous fermentation with K. marxianus.     

Genetic and enological analysis of selected Saccharomyces cerevisiae strains for wine production

The non‐wine Saccharomyces cerevisiae strain of 96581 was found to be a promising candidate for the production of white wine. It produced wines with fusel alcohols that were 57% higher than those produced by the wine yeasts studied and was also more efficient in the production of 2‐phenethyl acetate and 3‐methyl‐1‐butanol acetate. This study also shows that there is a difference in the ester‐formation efficiency for acetates relative to C6, C8 and C10 fatty acid esters for all the studied yeast strains. Therefore, it supports the view that other unidentified enzymes besides those regulated by ATF1 and ATF2 genes are involved in the production of ethyl esters of C6–C10 fatty acids. DNA analysis of the 25S, 18S, 5.8S and 5S ribosomal DNA genes in these strains showed high conservation. Despite the closely related nature of these yeast strains, the chemical profiles of the wines produced were significantly different.     

Fermentative capacity of Kluyveromyces marxianus and Saccharomyces cerevisiae after oxidative stress

Volatile compound production during alcoholic fermentation has been studied in the production of many beverages. Temperature, yeast strain, nutrients and pH have been identified as important factors in the production of volatile compounds. In addition, other factors could influence this production during the fermentation process as well. Oxidative stress could occur during yeast biomass production because oxygen is an essential nutrient that is added to the growth medium. The fermentation parameters and the volatile compound production of one Saccharomyces cerevisiae strain (MC4) and two Kluyveromyces marxianus strains (OFF1 and SLP1) were evaluated in relation to fermentation parameters after oxidative stress induced by hydrogen peroxide or menadione. These yeasts were compared with S. cerevisiae W303–1A and showed significant differences in ethanol production, ethanol yield and maximum ethanol production rate. K. marxianus (OFF1) showed better fermentative capacity after oxidative stress. The higher alcohol production decreased after oxidative stress by >35% after 72 h fermentation time, and the amyl alcohol decreased at a higher level (>60%); however, the isobutanol production increased after oxidative stress between 1.5 and 4 times. The yeasts produced significant concentrations of esters however ethyl lactate, ethyl caprylate and the ethyl caproate were not detected in the control fermentation, while in the stress fermentation they accounted for up to 3 mg/L. These results demonstrate that oxidative stress can play an important role in the final aroma profile; but it is necessary to guarantee adequate yeast growth to obtain the volatile compounds desired. Copyright © 2017 The Institute of Brewing & Distilling     

沙门氏菌污染豆腐干和牛肉干后代谢物的研究

鼠伤寒沙门氏菌可引发沙门氏菌病,且耐药性强,严重危害人畜健康。利用气相色谱-质谱法（Gas Chromatography - Mass Spectrometer,GC-MS）显示沙门氏菌接种于NB培养基、豆腐干和牛肉干培养基后的代谢物,采用主成分分析和正交偏最小二乘判别鉴别特征性和差异性代谢产物,结合沙门氏菌的基因注释分析特征性和差异性代谢产物可能的代谢路径。结果表明：沙门氏菌污染两种食品后有显著的生长,特征性和差异性代谢产物包括烷烃,酚类及小分子酸、醇等;沙门氏菌的基因注释表明存在大量的碳水化合物代谢基因,参与了1-丁醇的生成,因此1-丁醇是沙门氏菌污染豆腐干和牛肉干的典型代谢物。     

温度对固相微萃取法分析南果梨果酒香气的影响

应用顶空固相微萃取法(HS-SPME)和气质联用(GC-MS)快速测定南果梨果酒中的香气成分。设立不同的温度条件,研究温度对固相微萃法分析南果梨果酒香气成分的影响。结果表明,在不同温度下,酯类和醇类化合物是鉴定出的主要香气成分;乙醇、乙酸乙酯、2- 甲基-1- 丙醇、异戊醇、2- 甲基-1- 丁醇、丁酸乙酯、乙酸异戊酯、3- 甲硫基丙酸乙酯、苯乙醇、癸酸乙酯是不同温度下共有的成分,温度在40℃鉴定出的香气成分种类最多。