Enhancement of volatile aromatic compounds in black raspberry wines via enzymatic treatment

Robus coreanus Miquel is widely used in the production of Korean black raspberry (KBR) wine owing to its health benefits and commercial value. The effects of three different commercially available glycosidase enzymes on the volatile compounds in KBR wines were investigated with large‐scale fermentation to develop a high‐flavour‐quality wine. Volatile aroma compounds from the wines were analysed using headspace‐solid phase micro‐extraction‐gas chromatography–mass spectrometry (HS‐SPME‐GC–MS) and sensory evaluations were performed to evaluate the flavour characteristics. KBR wines treated with commercial enzymes yielded high concentrations of terpenes and esters compared with the control wine because the odourless non‐volatile glycosides in KBR wines were converted to their corresponding free forms by the enzymes. HS‐SPME‐GC–MS‐SIM analysis showed that the primary monoterpene compounds in KBR wines treated by the enzymes were myrtenol, linalool, citronellol and a significant quantity of compounds such as 2‐phenyl ethanol and ethyl benzoate, which contributed to the flavour of KBR wine, as determined by GC‐FID. KBR wines treated with the enzymes exhibited different sensory characteristics from the control wine owing to higher intensity of floral and fruity aromas. KBR wine treated with CYTOLASE PCL5 on a large scale exhibited the highest sensory preference. Copyright © 2017 The Institute of Brewing & Distilling     

A comparison of the influence of eight commercial yeast strains on the chemical and sensory profiles of freshly distilled Chinese brandy

The current study examined eight commercial Saccharomyces cerevisiae strains [Lalvin ICV‐D80, Lalvin FC9 EDV, Lalvin QA23, Lalvin RHST, Uvaferm 43, Enoferm Burgundy (BGY), Lalvin EC1118 and Lalvin M69] for their influence on young brandies, with a special emphasis on chemical, volatile and sensory characteristics. Results of the chemical analysis of the fermented wines showed that all of the strains exhibited a similar performance for ethanol production, but titratable acidity was more variable, with the highest being found in the yeast BGY‐derived wine and the lowest in the yeast QA23‐derived wine. Spirits produced using yeast FC9 EDV showed a significantly higher content of volatile alcohols, esters and acids, and conveyed to the brandy typical fruity and rosy notes. Brandies derived using yeast Uvaferm 43 presented the highest content of total benzene compounds and this brandy was characterized by rosy and onion attributes. Higher levels of varietal compounds and a medium rosy and slightly acidic and rancid nuances were produced when yeast QA23 was used. When using principal component analysis to classify the samples, there were four groups: group 1 ( ICV‐D80, Uvaferm 43 and BGY), group 2 (FC9 EDV), group 3 (QA23, RHST and EC1118) and group 4 (M69). This work sheds some light on the flavour complexity owing to the use of different commercial yeasts and provides useful information for the brandy‐maker regarding the choice of yeast for the fermentation based on the volatile profile. Copyright © 2012 The Institute of Brewing & Distilling     

Yeast strain affects 3‐isopropyl‐2‐methoxypyrazine concentration and sensory profile in Cabernet Sauvignon wine

Background and Aims: 3‐Isopropyl‐2‐methoxypyrazine (IPMP) is both a grape‐ and insect‐derived trace compound found in wine that can contribute green characters. There has been renewed interest in examining how wine IPMP concentrations can be modulated due to recent concerns regarding ladybug taint – an off‐flavour from IPMP extracted from Harmonia axyridis (Pallas) (multicoloured Asian lady beetle). This study sought to determine the influence of commercial Saccharomyces yeast strains on IPMP concentration in Cabernet Sauvignon wines and to describe their sensory impact. Methods and Results: Rehydrated juice from Cabernet Sauvignon concentrate was spiked with 30 ng/L IPMP and fermented in triplicate by yeast strains Lalvin BM45, Lalvin EC1118, Lalvin ICV‐D21 or Lalvin ICV‐D80. IPMP concentration was determined using headspace solid‐phase micro‐extraction coupled with gas chromatography mass spectrometry (HS‐SPME‐GC‐MS), and was unchanged from juice levels in wine fermented by EC1118, Lalvin D21 and Lalvin D80 but increased by 11 ng/L (29%) in wine fermented by Lalvin BM45. Yeast strains differed in their sensory impact on wine made from IPMP‐spiked juice for five aroma and four flavour attributes. Conclusions: HS‐SPME‐GC‐MS allows for sensitive measurement of IPMP that, for the first time, has demonstrated the capacity for wine yeast to affect IPMP concentration. Yeast strains demonstrate varying ability to mask green or ladybug taint characters in wine. Significance of the Study: This information should be useful in guiding selection of yeast strains for juices of high IPMP concentration, including those that are multicoloured Asian lady beetle‐affected, under‐ripe or from varieties with high methoxypyrazine loads such as Cabernet Sauvignon.     

Yeast and bacterial modulation of wine aroma and flavour

Wine is a highly complex mixture of compounds which largely define its appearance, aroma, flavour and mouth‐feel properties. The compounds responsible for those attributes have been derived in turn from three major sources, viz. grapes, microbes and, when used, wood (most commonly, oak). The grape‐derived compounds provide varietal distinction in addition to giving wine its basic structure. Thus, the floral monoterpenes largely define Muscat‐related wines and the fruity volatile thiols define Sauvignon‐related wines; the grape acids and tannins, together with alcohol, contribute the palate and mouth‐feel properties. Yeast fermentation of sugars not only produces ethanol and carbon dioxide but a range of minor but sensorially important volatile metabolites which gives wine its vinous character. These volatile metabolites, which comprise esters, higher alcohols, carbonyls, volatile fatty acids and sulfur compounds, are derived from sugar and amino acid metabolism. The malolactic fermentation, when needed, not only provides deacidification, but can enhance the flavour profile. The aroma and flavour profile of wine is the result of an almost infinite number of variations in production, whether in the vineyard or the winery. In addition to the obvious, such as the grapes selected, the winemaker employs a variety of techniques and tools to produce wines with specific flavour profiles. One of these tools is the choice of microorganism to conduct fermentation. During alcoholic fermentation, the wine yeast Saccharomyces cerevisiae brings forth the major changes between grape must and wine: modifying aroma, flavour, mouth‐feel, colour and chemical complexity. The wine bacterium Oenococcus oeni adds its contribution to wines that undergo malolactic fermentation. Thus flavour‐active yeasts and bacterial strains can produce desirable sensory results by helping to extract compounds from the solids in grape must, by modifying grape‐derived molecules and by producing flavour‐active metabolites. This article reviews some of the most important flavour compounds found in wine, and their microbiological origin.     

酿酒酵母对樱桃酒挥发性组分及感官品质的影响

鉴于酿酒酵母（Saccharomyces cerevisiae）对樱桃酒挥发性香气及感官品质的重要贡献,测定了5种商业化酿酒酵母的产香性能,以期从中挑选适用于樱桃酒酿造的优质发酵剂。结果表明,5种酵母发酵的樱桃酒基本理化指标无差异（P＞0.05）,但是挥发性组分含量却存在显著差异（P＜0.05）。Lalvin 2323与Lalvin 71B能够增加丁酸乙酯、己酸乙酯、苯甲醛、β-大马酮等多种挥发性物质的合成量,赋予樱桃酒更浓郁的果香和花香特征,且Lalvin2323的整体香气比Lalvin 71B更浓郁;Laffort B0123可以提高里那醇、异戊醇、乙酸异戊酯的含量,感官品质也较好;Laffort X16酿造的樱桃酒果香味寡淡,生青气味浓郁,评分较低;Laffort Cervisiae（AC）酿造的樱桃酒整体香气略显不足,评分最低。总体来看,酵母Lalvin2323发酵樱桃酒的感官品质优于其他酵母。     

The Influence of Yeast Strains on the Volatile Flavour Compounds of Chinese Rice Wine

In order to assess the influence of yeast strains on volatile flavour profiles of Chinese rice wine, small‐scale Chinese rice wine brewing was carried out with eight yeast strains from three different typical Chinese rice wine brewing regions. The volatile flavour compounds were extracted by headspace solid phase microextraction (HS‐SPME) and analyzed by gas chromatography‐mass spectrometry (GC‐MS). The volatile flavour profiles of the different Chinese rice wines showed statistically significant differences depending on the yeast strains used. Yeast strains from the Shaoxing region showed a higher capacity to produce the esters 2‐phenylethanol and 3‐methylthiopropanol, while yeast strains from the Shanghai region stood out for their production of branched‐chain higher alcohols. Chinese rice wine fermented with a yeast strain from the Jiangsu region had the highest levels of organic acids. Using principal component analysis of the Chinese rice wine volatile flavour compounds, the eight yeast strains could be classified into three groups according to their origins. This is the first report about the volatile flavour characteristics of Chinese rice wine yeast. The data obtained in this work shows that the yeast strains contributed significantly to the flavour differences of the Chinese rice wines from the different regions.     

Volatile composition and aromatic attributes of wine made with Vitisvinifera L.cv Cabernet Sauvignon grapes in the Xinjiang region of China: effect of different commercial yeasts

The Xinjiang region is a major grape- and wine-production area in China, but the region’s notably high temperatures in the summer and year-round intense sun exposure play negative roles in the aroma, complexity, and elegance of Cabernet Sauvignon wine. In this study, Cabernet Sauvignon grapes harvested in this region were fermented on an industrial scale using four commercial yeast strains (L2323, D254, RVA, and CECA) and spontaneous yeast (NF). The results showed that a total of 123 volatile compounds were detected and 15 volatile compounds significantly contributed their flavor notes to the wine’s overall aroma. The use of RVA and CECA strains resulted in wine with higher concentrations of higher alcohols, terpenes and norisoprenoids. However, the D254-fermented wine showed high level of esters and carbonyl compounds. Wine fermented with the L2323 and D254 strain possessed a stronger fruity aroma, whereas the RVA strain enhanced the herbaceous, chemical, and fatty aromas in wine. Principal component analysis revealed that a significant aromatic feature difference was observed in these wines after alcoholic and malolactic fermentation. The use of different commercial yeast strains altered the aromatic profile of Cabernet Sauvignon wine.     

Volatile profiles of Cabernet Gernischet wine under rain-shelter cultivation and open-field cultivation using solid-phase micro-extraction–gas chromatography/mass spectrometry

The volatile profiles of Vitis vinifera cv. Cabernet Gernischet wines in vintages 2010 and 2011 from rain-shelter cultivation and open-field cultivation were compared and detected by headspace solid phase micro-extraction with gas chromatography-mass spectrometry. The results showed that the number and concentration of volatile compounds quantified in wine were lower under rain-shelter cultivation compared with open-field cultivation. The strength of the fruity, fatty, caramel, and floral aromas of the 2010 vintage wines was lower under rain-shelter cultivation condition, and the compounds contributing to herbaceous aroma series were also lower with rain-shelter cultivation in the 2011 vintage wines. However, the strength of fruity, fatty, caramel, floral, and chemical aromas was higher with rain-shelter cultivation in vintage 2011. The cultivations in the two vintages could be clearly divided into three groups by principal component analysis. The difference between two treatments was significant in vintage 2010, whereas there was no significant difference in vintage 2011. The present work reveals the effects of rain-shelter cultivation on Cabernet Gernischet wine volatile compounds and explains that the technique is helpful in improving the wine quality in some rainy regions.     

香气活度值法结合PLSR用于梨酒特征香气物质筛选与鉴定

采用固相微萃取-气相色谱-质谱对市售3种梨酒香气物质进行分离鉴定,共检出43种挥发性成分,其中醇类16种、酯类15种、醛类4种、酮类2种、酚类1种、酸类3种和其他化合物2种。结合香气活度值(odor activity value,OAV)和偏最小二乘回归(partial least squares regression,PLSR)确定梨酒特征香气物质并推断其对梨酒香气的贡献程度。OAV结果表明:梨酒特征香气物质主要为异丁醇、1-辛醇、1-壬醇、苯乙醇、丁酸乙酯、3-甲基丁酸乙酯、乙酸异戊酯、己酸乙酯、辛酸乙酯、β-大马士酮、丁香酚。建立6个感官属性(发酵香、酸香、果香、花香、甜香、清香)与43种香气物质的PLSR模型表明,苯甲醇、正丁醇、丁二酸二乙酯的OAV小于1,但对梨酒的香气有贡献,经OAV确定的梨酒特征香气物质与发酵香和甜香属性具有很好的相关性,而在清香、酸香、果香和花香上的相关性不明显。     

不同酵母对赤霞珠桃红葡萄酒香气的影响

利用CY3079、Zymaflore X16、TXL和STR四种不同类型的商业酵母发酵赤霞珠新鲜桃红葡萄酒,采用顶空固相微萃取（HS-SPME）结合气相色谱质谱（GC-MS）联用技术,分别对酒精发酵结束和瓶储陈酿一年的葡萄酒样品进行香气物质的定性与定量分析。结果表明,4种酵母发酵的赤霞珠桃红葡萄酒中香气物质的种类相似,但其含量差异显著。酒精发酵结束阶段,CY3079和Zymaflore X16酵母发酵的桃红葡萄酒中脂肪酸乙酯的含量高于其他酵母发酵的酒样,使它们具有更加浓郁的果香、甜香和花香;而Zymaflore X16和STR酵母产生乙酸异戊酯和乙酸苯乙酯的能力较强。经过一年的瓶储陈酿,所有处理的桃红葡萄酒中脂肪酸乙酯和高级醇乙酸酯的含量显著下降,导致其果香的强度降低,同时减少了不同酵母发酵酒样之间的差异。     

The influence of yeast on the aroma of Sauvignon Blanc wine

The main objective of this study was to investigate the effect of different Saccharomyces cerevisiae wine yeast strains on the concentration of aroma-enhancing volatile thiols and fermentation metabolites in Sauvignon Blanc wine. Seven commercial wine yeast strains were selected based on their putative ability to modulate the concentrations of the fruity volatile thiols, 4-mercapto-4-methylpentan-2-one (4MMP), 3-mercapto-hexanol (3MH) and 3-mercapto-hexylacetate (3MHA). Each of these yeasts was used to produce Sauvignon Blanc wines under controlled conditions, in triplicate, in 20-L quantities. The levels of 4MMP, 3MH and 3MHA in these wines were quantified using the p-hydroxymercuribenzoate method. In addition, a total of 24 volatile yeast-derived fermentation aroma compounds were also quantified using headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME–GC–MS). Formal sensory analysis was conducted by 12 trained assessors and, additionally, a panel of 24 experienced wine industry professionals assessed the wines and ranked them in order of preference. The results indicated that the yeast strains varied significantly in terms of their capabilities to (i) produce volatile thiols and fermentation metabolites; and (ii) to modulate the varietal characters of Sauvignon Blanc wine. Yeast strains that produced the highest levels of volatile thiols were responsible for wines with the highest perceived intensity of fruitiness, and these wines were preferred by the tasting panels. While the ‘green’ characters in Sauvignon Blanc wines can be manipulated through vineyard management, the ‘tropical fruity’ characters appear to be largely dependent on the wine yeast strain used during fermentation. Therefore, the choice of yeast strain offers great potential to modulate wine aroma profiles to definable styles and predetermined consumer market specifications.     

Influence of locally-selected yeast on the chemical and sensorial properties of Albariño white wines

The use of selected yeast strains with improved or novel properties may promote wines with special and original quality attributes. In this paper, changes in the chemical composition (aroma compounds and polyphenols) and sensorial properties of Albariño white wines elaborated with the same must and selected yeast (named as 1, 2 and 3) have been studied in comparison with wines subjected to non-inoculated fermentation (control wine). The results indicated that yeast strain can significantly influence the aroma and polyphenol composition of the wines. Wines elaborated with strain 1 had a higher concentration of terpenes and norisoprenoids, which are compounds closely associated with the fruity and fresh character of Albariño white wines. These same wines had a lower concentration of flavan-3-ols, closely associated with the astringency and bitterness of the wine and the lowest browning potential. The formal sensory analysis conducted by 8 trained judges showed that wines elaborated with strain 1 were preferred by the tasting panel. Therefore, the selection of yeast strains could offer the possibility to modulate sensorial attributes related with the aroma and phenol composition in Albariño white wines.     

Engineering volatile thiol release in Saccharomyces cerevisiae for improved wine aroma

Volatile thiols, such as 4-mercapto-4-methylpentan-2-one (4MMP), 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA), are among the most potent aroma compounds found in wine and can have a significant effect on wine quality and consumer preferences. At optimal concentrations in wine, these compounds impart flavours of passionfruit, grapefruit, gooseberry, blackcurrant, lychee, guava and box hedge. The enzymatic release of aromatic thiols from grape-derived, non-volatile cysteinylated precursors (Cys-4MMP and Cys-3MH) and the further modification thereof (conversion of 3MH into 3MHA) during fermentation, enhance the varietal characters of wines such as Sauvignon Blanc. Wine yeast strains have limited and varying capacities to produce aroma-enhancing thiols from their non-volatile counterparts in grape juice. Even under optimal fermentation conditions, the most efficient thiol-releasing Saccharomyces cerevisiae wine strain known realizes less than 5% of the thiol-related flavour potential of grape juice. The objective of this study was to develop a wine yeast able to unleash the untapped thiol aromas in grape juice during winemaking. To achieve this goal, the Escherichia coli tnaA gene, encoding a tryptophanase with strong cysteine-beta-lyase activity, was cloned and overexpressed in a commercial wine yeast strain under the control of the regulatory sequences of the yeast phosphoglycerate kinase I gene (PGK1). This modified strain expressing carbon-sulphur lyase activity released up to 25 times more 4MMP and 3MH in model ferments than the control host strain. Wines produced with the engineered strain displayed an intense passionfruit aroma. This yeast offers the potential to enhance the varietal aromas of wines to predetermined market specifications.     

Yeast derivatives (extracts and autolysates) in winemaking: Release of volatile compounds and effects on wine aroma volatility

A qualitative study of volatile compounds in three commercial yeast extracts and autolysates was performed by solid-phase microextraction-gas chromatography with mass spectrometric and olfactometric detection; their addition to white wines and their effect on wine aroma composition were investigated by analytical, olfactometric and sensory evaluations. More than 160 volatile compounds were detected in the headspace of the commercial powders (some not previously reported in literature), and their olfactory characters were described. Yeast derivatives strongly modified wine aroma composition, either affecting the volatility of wine aroma compounds or by releasing exogenous volatiles. Dosage appeared to be fundamental: low amounts increased the volatility of some esters, giving more flowery and fruity notes to the wine; higher amounts increased fatty acid content in the wine headspace, producing yeasty, herbaceous and cheese-like smells. Sensory tests demonstrated that yeast derivatives would not be suitable for wines with a typical varietal aroma.