Effects of cofermentation and sequential inoculation of Saccharomyces bayanus and Torulaspora delbruckii on durian wine composition

This work investigated the effects of cofermentation and sequential inoculation of Torulaspora delbrueckiiBiodiva and Saccharomyces bayanusEC‐1118 on chemical and volatile components of durian wines. Cofermentation and sequential inoculation resulted in higher production of ethanol (6.2% and 7.7% v/v, respectively) relative to the control (5.3% for S. bayanus and 5.8% for T. delbrueckii). Further, cofermentation and sequential inoculation produced higher amounts of acetyl esters and higher alcohols especially isoamyl alcohol and 2‐phenylethyl alcohol than monoculture fermentation. Most endogenous sulphur volatiles, especially disulphides that impart a character‐impact durian odour, declined to trace levels, but new ones such as thioesters were formed. Sulphur volatiles in the durian wines fermented by cofermentation and sequential inoculation accounted for 0.03% and 0.05% of total peak area. The study suggests that the use of S. bayanus in conjunction with non‐Saccharomyces such as T. delbrueckii may improve the aromatic intensity and complexity of durian wine.     

外源添加单一氨基酸对桑葚酒风味品质的影响

为探究外源添加氨基酸在改善桑葚酒风味品质中的影响,在桑葚果汁中分别添加400 mg/L的异亮氨酸（Ile）、亮氨酸（Leu）、苯丙氨酸（Phe）和缬氨酸（Val）制备桑葚酒,并分析桑葚酒理化指标、挥发性风味物质和感官品质。结果表明,与对照相比,外源添加单一氨基酸可显著增加桑葚酒的挥发性风味物质含量（42.38～84.58 mg/L）（P＜0.05）,添加Ile显著增加活性戊醇、乙酸活性戊酯含量,添加Leu显著增加异戊醇、乙酸异戊酯含量,添加Phe显著增加苯乙醇和乙酸苯乙酯的含量,添加Val显著增加异丁醇和乙酸异丁酯含量,添加四种氨基酸都能增加辛酸乙酯的含量（P＞0.05）;添加Phe可提高桑葚酒花香,添加Ile、Leu或Val提高果香,添加四种氨基酸的桑葚酒的口感评分均显著提高（P＜0.05）。     

Effects of overexpression of the alcohol acetyltransferase‐encoding gene ATF1 and disruption of the esterase‐encoding gene IAH1 on the flavour profiles of Chinese yellow rice wine

Alcohol acetyltransferase (AATase), which is mainly encoded by ATF1, is one of the most important enzymes for acetate ester synthesis. On the other hand, isoamyl acetate is degraded into a higher alcohol under the catalysis of IAH1‐encoded esterase. In this study, Chinese Saccharomyces cerevisiae was used as the parent strain to construct an ATF1 overexpression and IAH1 disruption mutant. The results show that after 5 days of pre‐fermentation, the concentrations of ethyl acetate, isoamyl acetate and isobutyl acetate in the yellow rice wines fermented with EY1 (pUC‐PIAK) increased to 468.94 mg L^?1 (which is approximately 22‐fold higher than that of the parent cell RY1), 99.86 and 7.69 mg L^?1 respectively. Meanwhile, isoamyl alcohol production was reduced to 56.37 mg L^?1 (which is approximately 50% of that produced by the parent strain RY1). Therefore, ATF1 overexpression and IAH1 disruption can significantly increase acetate esters contents and reduce isoamyl alcohol content in Chinese yellow rice wine, thereby paving the way for breeding an excellent yeast strain for high‐quality Chinese yellow rice wine production.     

Effects of branched‐chain amino acid addition on chemical constituents in lychee wine fermented with Saccharomyces cerevisiae

This study investigated the impact of single branched‐chain amino acid addition (L‐valine, L‐leucine, L‐isoleucine) on nonvolatile and volatile constituents in lychee wine fermented with Saccharomyces cerevisiae MERIT.ferm. The individual addition of branched‐chain amino acids decreased the consumption of proline with significantly different rates. The lychee wine with added L‐leucine and L‐isoleucine had higher odour activity values (OAVs) of isoamyl alcohol, active amyl alcohol and isoamyl acetate. The lychee wine with added L‐valine had higher OAVs of isobutyric acid and isobutyl alcohol (5.55 and 2.98, respectively), which were lower in the wine with added L‐leucine (2.91 and 1.02, respectively) or L‐isoleucine (3.43 and 1.73, respectively) relative to the control wine (4.18 and 1.77, respectively), suggesting interactive effects among the amino acids. These findings demonstrated that lychee wine aroma can potentially be manipulated via the addition of selected branched‐chain amino acids.     

李子果酒主发酵过程中理化指标及挥发性成分变化分析

该研究对李子果酒主发酵过程中的理化指标进行测定,并采用顶空固相萃取-气相色谱-质谱（HS-SPME-GC-MS）联用技术对其挥发性成分进行分析。结果表明,在李子果酒主发酵过程中,随着发酵时间的延长,pH值、酒精度呈先升高后趋于稳定的趋势;总酸、总糖含量呈先下降后趋于稳定的趋势;挥发酸含量呈上升趋势。主发酵结束后,李子果酒的酒精度为11.10%vol、总酸含量为9.13 g/L、pH值为3.76、挥发酸含量为0.25 g/L、总糖含量为22.90 g/L。主要变化的挥发性物质为6种醇类（乙醇、1-己醇、异戊醇、异丁醇、顺式-3-己烯-1醇、苯基乙醇）和6种酯类（乙酸乙酯、乙酸异戊酯、辛酸乙酯、乙酸己酯、己酸乙酯、癸酸乙酯）。通过对李子果酒主发酵过程动态变化分析,为提高李子果酒品质提供理论依据。     

Mead production: effect of nitrogen supplementation on growth,fermentation profile and aroma formation by yeasts in mead fermentation

Mead is an alcoholic beverage, produced since ancient times, resulting from an alcoholic fermentation of diluted honey by yeasts. When it is produced in a traditional manner, mead producers can encounter several problems related to a lack of essential nutrients, such as available nitrogen. Thus, the aim of this study was to evaluate the effect of nitrogen addition to honey‐must on the fermentation performance of two Saccharomyces cerevisiae wine yeasts, QA23 and ICV D47, as well as on the mead composition and production of volatile aroma compounds. A portion of honey‐must was supplemented with diammonium phosphate (DAP) to achieve the nitrogen concentration required by yeast to complete alcoholic fermentation. The supplementation with DAP reduced the fermentation length to around 7 days, but not all sugars were fully consumed, suggesting that other factors could be interfering with yeast growth. For both yeasts the specific growth rate and final biomass were higher in musts supplemented with DAP. Mead final composition was similar under the two experimental conditions. Analysis of the volatile profile revealed that the concentrations of the volatile fatty acids and volatile phenols were higher in meads supplemented with DAP. The concentrations of ethyl hexanoate, ethyl octanoate and isoamyl acetate were above their perception threshold and were higher in meads supplemented with DAP, which could contribute to the enhancement of the fruity character. This study could be useful for the optimization of mead production and quality improvement. Copyright © 2015 The Institute of Brewing & Distilling     

Influence of carbon and nitrogen source on production of volatile fragrance and flavour metabolites by the yeast Kluyveromyces marxianus

The yeast Kluyveromyces marxianus produces a range of volatile molecules with applications as fragrances or flavours. The purpose of this study was to establish how nutritional conditions influence the production of these metabolites. Four strains were grown on synthetic media, using a variety of carbon and nitrogen sources and volatile metabolites analysed using gas chromatography–mass spectrometry (GC–MS). The nitrogen source had pronounced effects on metabolite production: levels of the fusel alcohols 2‐phenylethanol and isoamyl alcohol were highest when yeast extract was the nitrogen source, and ammonium had a strong repressing effect on production of 2‐phenylethyl acetate. In contrast, the nitrogen source did not affect production of isoamyl acetate or ethyl acetate, indicating that more than one alcohol acetyl transferase activity is present in K. marxianus. Production of all acetate esters was low when cells were growing on lactose (as opposed to glucose or fructose), with a lower intracellular pool of acetyl CoA being one explanation for this observation. Bioinformatic and phylogenetic analysis of the known yeast alcohol acetyl transferases ATF1 and ATF2 suggests that the ancestral protein Atf2p may not be involved in synthesis of volatile acetate esters in K. marxianus, and raises interesting questions as to what other genes encode this activity in non‐Saccharomyces yeasts. Identification of all the genes involved in ester synthesis will be important for development of the K. marxianus platform for flavour and fragrance production. Copyright © 2014 John Wiley & Sons, Ltd.     

Effects of sugar concentration on mango wine composition fermented by Saccharomyces cerevisiae MERIT.ferm

This study investigated the effect of initial sugar concentrations (^°Brix of 17, 23 and 30) on mango wine composition fermented by Saccharomyces cerevisiae MERIT.ferm. It was found that growth rate and maximum cell population were inversely correlated with initial sugar levels with the fastest growth rate and largest cell population in the low sugar fermentation. However, the cell population in the low and medium sugar fermentation declined significantly (from 8.7 and 8.2 log to 2 and 2.8 log, respectively) relative to the high sugar fermentation in which cell populations remained stable upon reaching the stationary phase (7.7 log). Glycerol production increased with increasing sugar content in low (13.4 g L^?1), medium (14.5 g L^?1) and high (15.9 g L^?1) sugar fermentation. In addition, high sugar fermentation had a negative impact on volatile production with significantly lower amounts of acetate esters (1.5 mg L^?1) but more acetic acid (0.54 g L^?1) compared to the low (5.0 mg L^?1 and 0.44 g L^?1, respectively) and medium (3.7 mg L^?1 and 0.49 g L^?1, respectively) sugar fermentations. Furthermore, volatiles especially terpene hydrocarbons (α‐caryophyllene was released) present in mango juice were significantly metabolised after fermentation, while numerous new volatile compounds (such as isobutyl alcohol, isoamyl alcohol, ethyl and acetate esters) were produced. Some terpene alcohols were released and converted into corresponding acetyl esters. This may indicate that the mango wines fermented with different levels of sugars would have different flavour aromas.     

Inhibition of the decrease of volatile esters and terpenes during storage of a white wine and a model wine medium by glutathione and N-acetylcysteine

Glutathione and N‐acetylcysteine, each at 20 mg L^?1, were tested as inhibitors of the decrease of volatile esters and terpenes during storage of Debina white wine. Moreover, the inhibition of the decrease of isoamyl acetate, ethyl hexanoate and linalool in a model wine medium by glutathione and N‐acetylcysteine, each at 0–20 mg L^?1, was also tested. Several volatiles, such as isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate and linalool, decreased during wine storage. Glutathione or N‐acetylcysteine significantly restricted the decrease of these volatiles. In the model medium, each thiol inhibited the decrease of the three volatiles in a dose‐dependent manner. N‐acetylcysteine inhibited the decrease of all three volatiles at 2.5 mg L^?1 while glutathione at 2.5 or 5.0 mg L^?1. The present results indicate that glutathione and N‐acetylcysteine may be taken into account as potent inhibitors of the disappearance of aromatic esters and terpenes in wines.     

The impact of maturation on concentrations of key odour active compounds which determine the aroma of tequila

Samples of non‐mature and añejo (matured) tequila of the same brand/provenance were analysed using GC–MS and gas chromatography olfactometry (GC‐O)/aroma extract dilution analysis (AEDA) to provide quantitative data on the most odour active compounds that contribute to the aroma of these spirits. Extracts of non‐mature tequila were characterized by 26 odour‐active regions, which included ethyl hexanoate, ethyl octanoate, 2‐phenylethyl acetate, β‐damascenone, isoamyl alcohol and octanoic acid as the most odour‐active compounds (flavour dilution, FD, factor ≥ 6561). In contrast, extracts of the mature spirit showed 36 odour‐active zones, where the compounds with the highest FD factors (6561) were ethyl hexanoate, ethyl octanoate, 2‐phenylethyl acetate, isoamyl alcohol, phenethyl alcohol, guaiacol, 4‐ethyl guaiacol, vanillin, cis/trans whisky lactones, β‐damascenone and octanoic acid. The aromagram of mature tequila was thus differentiated from that of the non‐mature spirit owing to the presence of cask‐extractive compounds and the increased FD factors of certain terpenes, higher alcohols and acetals. This study provides a comprehensive and quantitative understanding of changes in key odourants of tequila as a result of the maturation process and also reveals a further characterization of the likely impact of each compound on overall spirit flavour, in terms of odour activity values. Copyright © 2016 The Institute of Brewing & Distilling     

机械修剪方式下不同叶幕厚度对晋中地区赤霞珠葡萄酒香气的影响

以酿酒葡萄赤霞珠为试材,研究机械修剪方式下3?种不同叶幕厚度（70、85、100?cm）对葡萄酒香气的影响。结果表明：70?cm的叶幕厚度能够显著地增加赤霞珠葡萄酒中总酚、单宁和总花色苷的含量,但不利于香气物质的积累。85?cm的叶幕厚度能够增加高级醇、脂肪酸、醛酮类和挥发性苯类衍生物的含量,其中具有花香、果香与奶酪味的3-甲基-1-丁醇、乙酸乙酯、β-大马士酮、苯乙醛、苯乙醇、乙酸异戊酯、己酸乙酯的香气值均高于其他处理组。     

Protection of volatile esters and terpenes during storage of a white wine and a model wine medium by a mixture of N-acetyl-cysteine and caffeic acid

A mixture of N-acetyl-cysteine + caffeic acid, at 10 + 30 mg/L respectively, was tested as inhibitor of the decrease of volatile esters and terpenes during storage of Debina white wine. Moreover, the inhibition of the decrease of isoamyl acetate, ethyl hexanoate and linalool in a model wine medium by the mixture, at 1.25 + 3.75 to 10 + 30 mg/L, was tested. Several volatiles, such as isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate and linalool, decreased during wine storage. The mixture of N-acetyl-cysteine + caffeic acid restricted the decrease of these volatiles to a large extent. In the model medium, the mixture inhibited the decrease of the three volatiles in a dose dependent manner. It was active at any concentration tested. The present results indicate that mixture of N-acetyl-cysteine + caffeic acid, containing each compound at low concentration, may be taken into account as an effective inhibitor of the disappearance of volatile aroma in wines.     

模糊数学结合响应面法优化葛根酒发酵工艺参数及其香气成分分析

为消除主观因素对感官评价的影响,以宜宾葛根为原料,采用模糊数学结合响应面法对葛根酒发酵工艺进行优化。在单因素实验的基础上,选取发酵初始pH、发酵温度、酵母添加量为影响因素,以通过模糊综合评价得到的品质等级值为响应值,运用Box-Behnken中心组合试验设计建立数学模型,进行响应面分析,并采用顶空固相微萃取结合气相色谱-质谱联用技术(HS-SPME/GC-MS)对葛根酒的香气成分进行检测。结果表明:葛根酒最优发酵条件为发酵初始pH5.5、发酵温度30 ℃、酵母接种量0.5%。在此条件下,感官评价等级值为3.68;葛根酒中共检测出30种香气成分,醇类物质含量为8.414 mg/L,以异戊醇、苯乙醇、异丁醇和异丙醇为主;酯类物质含量为2.229 mg/L,其中乙酸乙酯、乙酸苯乙酯、乙酸异戊酯、辛酸乙酯、己酸乙酯含量较高;此外还检测出酸类、醛类、酮类物质,如乙酸、己酸、辛酸、乙缩醛、3-羟基-2-丁酮等,这些香气物质相互融合协调,构成了葛根酒独特的风味。     

Impact of cover crops in vineyard on the aroma compounds of Vitis vinifera L. cv Cabernet Sauvignon wine

This study compared the influence of different cover crops with clean tillage on wine aroma compounds of 5-year-old Cabernet Sauvignon vines. White clover, alfalfa, and tall fescue were used in the vineyard and compared with clean tillage. Aroma compounds of wine were analysed by solid-phase microextraction gas chromatography–mass spectrometry (SPME-GC/MS). Forty-seven volatile compounds were identified and quantified. Wines made from grapes grown with various cover crops had higher levels of aroma compounds. Ethyl acetate, isoamyl acetate, ethyl octanoate, ethyl hexanoate, phenylethyl acetate, isoamyl alcohol, linalool, citronellol, β-damascenone, α-ionone, and 5-amyl-dihydro-2(3H)-furan were the impact odorants of sample wines. Wines from cover crop also had higher contents of these impact odorants than the control. For different cover crops, alfalfa sward yielded the highest levels, followed by the tall fescue treatment. According to the data analysis of aroma compounds and sensory assess, permanent cover crop may have the potential to improve wine quality.     

可同化氮源磷酸氢二铵对发酵型猕猴桃酒品质的影响

为考察可同化氮源磷酸氢二铵（diammonium phosphate,DAP）对发酵型猕猴桃酒品质的影响,向猕猴桃汁中添加100～400 mg/L（氮质量计,下同）的DAP,并对发酵所得猕猴桃酒的基本理化指标、潜在有害醇类物质、营养组分和香气物质进行检测与分析。结果表明：添加100～400 mg/L的DAP均可以加快起酵后48 h内的乙醇发酵速度,并显著降低了猕猴桃酒中高级醇和甲醇等潜在有害醇类物质产量。特别是添加300 mg/L的DAP时,猕猴桃酒的总高级醇和甲醇产量分别下降了42.84%和20.1%;尽管添加DAP显著降低了酒中的氨基酸总量,但却对猕猴桃酒中的VC和总酚含量没有显著影响;添加DAP显著增加了猕猴桃酒的乙酸酯类和乙酯类香气物质含量,其中,添加300 mg/L的DAP可以显著增加乙酸乙酯、正己酸乙酯、正辛醛、庚醇和1-辛烯-3-醇等香气物质含量,从而使猕猴桃酒果香和花香较为浓郁。因此,添加适量的可同化氮源DAP可以提升发酵型猕猴桃酒的品质。     

Fermentation temperature and the phenolic and aroma profile of persimmon wine

Persimmon wine may offer nutritional and medicinal value as it contains compounds that may be beneficial to health. Product quality is impacted by fermentation and this study investigated the influence of different fermentation temperatures on the phenolic content, aroma profile and antioxidant activity of persimmon wine. Low ethanol concentration and high residual sugar content were found in wine fermented at low temperature (15°C) leading to sluggish fermentation. The majority of phenolic compounds determined by spectrophotometric and HPLC methods increased as temperature increased from 15 to 25°C, and then decreased at 30°C. However, total tannins, total flavonids and antioxidant activity, including reducing power and radical scavenging with DPPH, hydroxyl and ABTS, were enhanced by elevated temperature. For wine aroma, GC–MS demonstrated increased isoamyl alcohol, phenylethyl alcohol, acetic acid 2‐phenylethyl ester, decanoic acid ethylester and 1‐butanol‐3‐methyl‐acetate. These results provided some basic insights for the quality control and commercial development of persimmon wine. © 2018 The Institute of Brewing & Distilling     

Effect of γ‐aminobutyric acid supplementation on the composition of Chinese rice wine

This study investigated the effect of γ‐aminobutyric acid (GABA) supplementation on the composition of Chinese rice wine. GABA was added at 188.5 and 377 mg/L at the beginning of primary fermentation or post‐fermentation. Addition of GABA during primary fermentation had no impact on alcohol and total acid formation or the utilisation of sugar. However, total free amino acids, total essential amino acids and GABA in rice wine supplemented with GABA were significantly lower than the control rice wine without supplementation. Alcohol formation, total acid, sugar content and total essential amino acids were similar compared with the control. However, the GABA post‐supplementation was significantly higher, suggesting that GABA supplementation post‐fermentation process could enhance the GABA content in rice wine. © 2018 The Institute of Brewing & Distilling     

Effects of yeast fermentation on transforming the volatile compounds of unsalted pork hydrolysate

This study investigated the possibility of transforming unsalted pork hydrolysate into a liquid seasoning by studying volatile compound production through yeast fermentation. The yeasts used included a typical soya sauce yeast and three wine yeasts. The yeasts inoculated in the glucose supplementary pork hydrolysate increased by approximately 2.0 log of CFU mL⁻¹ within 24 hours at 30°C without adding salt. Yeast fermentation largely depleted the abundant aldehydes (hexenal) present in unfermented pork hydrolysate to trace levels with the formation of ethanol, corresponding alcohols and carboxylic acids. The wine yeasts showed higher production of fruity esters such as ethyl acetate and isoamyl acetate, whereas the soya sauce yeast produced more ketones such as acetone and 2-heptanone. This study revealed a potential method of producing a value-added meat hydrolysate from pork by-product.     

Inhibition of the decrease of volatile esters and terpenes during storage of a white wine and a model wine medium by caffeic acid and gallic acid

Caffeic acid and gallic acid were tested as inhibitors of the decrease of volatile acetate esters, ethyl esters and terpenes during storage of a white wine and a model wine medium. Wine and model wine samples were analysed by SPME along with GC–MS. At t = 0, no effect on the concentration of any volatile was observed as a result of adding each phenolic acid in any of wine or model wine samples. Many esters, such as isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, and linalool decreased during storage of Debina-white wine for up to 20 months. Caffeic acid and gallic acid at 60 mg/L inhibited the decrease of these volatiles. Isoamyl acetate, ethyl hexanoate and linalool decreased during storage of the model wine medium containing 0, 20 or 40 mg/L SO₂. Caffeic acid and gallic acid inhibited the decrease of three volatiles; SO₂ inhibited the decrease of isoamyl acetate and ethyl hexanoate. In some cases, SO₂ increased the inhibitory action of two phenolic acids. The inhibitory action of caffeic acid and gallic acid was dose dependent in the range 0–60 mg/L. Caffeic acid was active at 7.5 mg/L while gallic acid at 15 mg/L.Present results indicate that caffeic acid and gallic acid may be taken into account as potent inhibitors of the disappearance of aromatic volatile esters and terpenes in wines at concentrations similar to those existing in wines.     

Characterization of volatile compounds in Fen‐Daqu – a traditional Chinese liquor fermentation starter

Fen‐Daqu is a saccharifying agent and fermentation starter for the production of Chinese liquor Fen (alcoholic spirit) and Fen traditional vinegar. The volatile compounds produced at seven incubation steps were analysed by HS‐SPME‐GC‐MS. A total of 83 major volatile compounds were identified, including 23 esters, 8 acids, 24 alcohols, 18 ketones and aldehydes, 6 pyrazines and 4 acetals. Data obtained by HS‐SPME‐GC‐MS were subjected to principal component analysis. The trajectory plots of volatile compounds in Fen‐Daqu samples obtained during successive steps of incubation were revealed. The major compounds that contributed to discrimination were hexanal, (E)‐2‐octenal, (Z)‐2‐octen‐1‐ol, nonanoic acid, 1‐octanol, 2‐decen‐1‐ol, hexyl acetate, (E)‐2‐octen‐1‐ol, acetic acid, ethyl acetate, phenylethyl alcohol, ethyl alcohol, octanoic acid, 1‐octanol, 3‐methyl‐2‐buten‐1‐ol and pyrazines. Copyright © 2012 The Institute of Brewing & Distilling