Enhancement of Aroma in White Wines Using a β-Glucosidase Preparation From Debaryomyces pseudopolymorphus (A-77)

The liberation of aromas in young wines is presently one of the most interesting subjects in enology. The hydrolysis of the glycosidic compounds (aroma precursors) of grape varieties from Castilla-La Mancha (Spain) has been studied, using an enzymatic preparation from Debaryomyces pseudopolymorphus (A-77) with high β-glucosidase activity. This preparation was added to the wines and its effect was observed at 6 and 12 days of incubation. Enzymatic activity was studied quantifying both the precursors that were not hydrolysed and those that liberated volatile compounds by gas chromatography/mass spectrometry.

The results were compared with a control wine (without enzyme) and also with a wine treated with a commercial fungal enzyme preparation specifically recommended for the liberation of aromas in wines. It was observed that the enzymatic extracts from D. pseudopolymorphus were adequate and that they could compete with the commercial preparations since the volatiles liberated were more controlled and it took less time to get the same results. To complete the study, the results obtained in regards to the liberation of volatiles were corroborated by sensory analysis.     

Effect of skin contact on bound aroma and free volatiles of Listán blanco wine

Listán blanco is the major grape variety of the Canary Islands. Aroma precursors in musts and free volatiles in wines and their variations due to the skin contact process (10 °C and 0–12 h of maceration) were determined in samples of the Listán blanco grape variety. Aroma precursors of must were isolated by absorption on XAD-2 resin and the aglycone liberated by means of acid hydrolysis. Free volatiles from wines and from aroma precursors were extracted with dichloromethane and then analysed by GC-MS. The results of two consecutive vintages show that only aroma precursors of some terpenes and phenols may affect the final wine aroma. However, the majority of the free compounds of the wines did not present differences in content that could be related to the skin contact process.     

Influence of several enzymatic treatments on aromatic composition of white wines

Albariño wines were treated enzymatically at industrial scale, and the effect of both aromatic extracting and clarifying enzymes on the aroma were evaluated and compared. A commercial enzyme (Endozym cultivar) was added during maceration to two musts; clarification enzyme (Depectil clarification) was added to other two wines after fermentation (control wines), and in other four wines were applied the both commercial enzymatic treatments (Endozym cultivar and Depectil clarification, or Rapidase Xpress and Depectil clarification). Volatile compounds were analysed by gas-chromatography (FID and mass spectrometric detection) and by sensory analysis. All the wines, independently of the type of enzyme, presented different aromatic characteristics in comparison to the control wines, above all the wines obtained from the enzyme applied during maceration which showed the highest contents in varietal compounds and in other desirable compounds, such as benzene derivatives, ethyl esters or phenylethyl acetate. The employ of maceration and clarification enzymes as a whole seemed not be suitable because this combination could be cancel the released aromas by the glycosidase enzyme during the pellicular contact. Principal component analysis of chemical data corroborated these effects, because a very clear and good differentiation was achieved between the wines treated only with the maceration enzymes (glycosidase activity) opposite to the wines subjected to the other enzymatic treatments. These results are also closely related to the sensory analysis, which indicated that the glycosidase enzymatic treatment seemed to be effective for the improvement of the aroma of Albariño 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.     

Bound aroma compounds of Marmajuelo and Malvasía grape varieties and their influence on the elaborated wines

Marmajuelo and Malvasía are two white grape varieties grown in Spain (Canary Islands), the former only in the Canary Islands, while the latter is a variety widely spread throughout the world. At the present time, the oenological potential of these varieties grown in the Canaries has not yet been studied. Aroma precursors in musts and skins, and free volatiles in wines were determined in samples of both varieties. Aroma precursors of must and skins were isolated by absorption on XAD-2 resin, and the aglycone liberated by means of acid hydrolysis. Free volatiles from wines and from aroma precursors were extracted with dichloromethane and then analysed by GC–MS. The analysis of glycosidic aroma precursors showed that Malvasía variety presented higher contents of terpenes in grapes than those of Marmajuelo variety. In addition, some precursors of benzenic compounds presented higher contents in the musts of Malvasía with respect to those in the musts of Marmajuelo. The main difference in wine volatile composition was that cis-3-hexen-1-ol, ethyl acetate and γ-nonalactone compounds showed a significantly higher mean content in Malvasía wines than in Marmajuelo wines. Among the aroma precursors analysed, only α-terpineol, linalool oxides, 4-allyl-2,6-dimethoxyphenol, 2-methoxy-4-vinylphenol, 4-hydroxybenzaldehyde, vanillin and benzyl alcohol showed contents in grapes comparable to the levels observed in wine volatile compounds.     

Bound aroma compounds of Gual and Listán blanco grape varieties and their influence in the elaborated wines

Listán blanco and Gual are two white grape varieties grown in Spain (Canary Islands) and Gual is also grown in Portugal (Madeira Island). Wine quality could be improved by exploiting the varietal characteristics present in grapes as aroma precursors. At the present time, the enologic potential of these varieties has not yet been studied. Aroma precursors in musts and skins, and free volatiles in wines were determined in samples of both varieties. Aroma precursors of must and skins were isolated by absorption on XAD-2 resin and the aglycone liberated by means of acid hydrolysis. Free volatiles from wines and from aroma precursors were extracted with dichloromethane and then analysed by gas chromatography-mass spectrometry (GC–MS). Among the aroma precursors analysed, only α-terpineol, linalool and linalool oxides, 4-allyl-2,6-dimethoxyphenol, 2-methoxy-4-vinylphenol, 4-hydroxybenzaldehyde, vanillin and benzyl alcohol showed contents in grapes comparable to the levels observed in wine volatile compounds.     

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     

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。     

Effects of Different β‐D‐Glycosidases on Bound Aroma Compounds in Muscat Grape Determined by HS‐SPME and GC‐MS

Important “floral” aromas naturally occur in grapes predominantly as flavourless glycoconjugate precursors. Since these aroma compounds can be released by hydrolysis, different glycosidase enzymes can potentially contribute different aromas to wines. In this paper, we first established a procedure for profiling the free and bound volatile compounds in grape using GC‐MS combined with headspace solid‐phase microextraction (HS‐SPME). Comparison of the free and bound aroma compounds revealed that non‐volatile glycosides, known as aroma precursors, occur in high concentrations in musts. Among all compounds identified, 11 were fully quantified according to established standard calibration curves, while others were semi‐quantified. Using three different glycosidase enzymes, a total of 38 bound volatile compounds were identified in Muscat grape, including terpenes, higher alcohols, C‐6 compounds, and phenols, among others. The different enzymes had significant effects on the varietal aroma. Principal component analysis indicated that the characteristic aroma hydrolyzed by the commercial enzyme AR2000 was clearly different from that produced by other enzymes.     

Assessing the Potential Content of Ethyl Carbamate in White,Red, and Rosé Wines as a Key Factor for Pursuing Urea Degradation by Purified Acid Urease

The ethyl carbamate (EC) content of a wine after a given temperature‐time storage was theoretically predicted from the potential concentration of ethyl carbamate (PEC), as determined via an accelerated EC formation test. Such information was used to decide whether an enzymatic treatment was needed to reduce the wine urea level before bottling/aging. To this end, 6 white, red, and rosé wines, manufactured in Italy as such or enriched with urea, were tested for their PEC content either before or after enzymatic treatment using a purified acid urease preparation derived from Lactobacillus fermentum. The treatment was severely affected by the total phenolic content (TP) of the wine, the estimated pseudo‐first‐order kinetic rate constant for NH₃ formation reducing by a factor of approximately 2000 as the TP increased from 0 to 1.64 g L^‐1. Such a sensitivity to TP was by far greater than that pertaining to a killed cell‐based enzyme preparation used previously. Urea hydrolysis was successful at reducing EC concentration in wines with low levels of TP and other EC precursors.     

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.     

Volatile aroma and sensory analysis of black raspberry wines fermented by different yeast strains

Robus coreanus Miquel is a small berry fruit used for Korean black raspberry (KBR) wine‐making. Twelve different yeast strains were investigated by laboratory‐scale fermentation to develop a wine with a high flavour quality. Volatile aroma compounds from the wines were analysed using headspace–solid phase microextraction–gas chromatography–mass spectrometry and sensory evaluation was performed to evaluate the flavour characteristics. The volatile aroma compounds that mostly contributed to the flavour of KBR wines were those related to fruity (esters) and floral (terpenes) aromas. Fifteen out of the 67 identified volatile compounds showed higher odour activity values than other compounds in the wines, and these compounds were considered as important contributors to the final aromas of the wine. Additionally, the KBR wine fermented by the M1 yeast strain had the highest sensory preference because of higher fruity and floral aroma characters compared with other wines. In addition to the M1 strain, the other yeast strains that produced favourable sensory characteristics included Enoferm CSM, Uvaferm VRB, Lalvin ICV GRE, Lalvin ICV Opale and LevureSeche Active. Of these strains, the M1 strain produced a particularly excellent black raspberry wine, and thus could be applied for further large‐scale production of black raspberry wines. It is also expected that this work will expedite research on the production of high‐quality black raspberry wines with beneficial physicochemical properties, functionality and good sensory characteristics. Copyright © 2015 The Institute of Brewing & Distilling     

Micro-oxygenation and oak chip treatments of red wines: Effects on colour-related phenolics,volatile composition and sensory characteristics. Part I: Petit Verdot wines

In this paper, the effects of micro-oxygenation before malolactic fermentation and oak chip treatments on Petit Verdot red wines have been evaluated. Our attention was focused on the colour characteristics, the phenolic compounds related to the colour of red wine, the volatile compounds, and the sensory characteristics of the wines. The micro-oxygenation treatment promoted the stabilisation of red wine colour by increasing the formation of colour-related phenolic compounds (higher concentrations of pyranoanthocyanins and anthocyanin-ethyl-flavan-3-ol adducts). Red wine aroma quality was improved with the addition of oak chips (eugenol and 4-vinyl-guaiacol concentration increased). Micro-oxygenation treatment resulted in higher scores for the plum/currant and spicy attributes, as well as the appearance of tobacco and nutty notes which were absent in the non-treated wines. Nevertheless, the typical oak chip aromas (vanilla and woody) were observed to a lesser extent in wines obtained by micro-oxygenation.     

蛇龙珠营养系干红葡萄酒中的挥发性风味物质

确定蛇龙珠不同营养系葡萄酒中挥发性风味物质的差异及对其感官品质的影响。利用顶空固相微萃取和气相色谱-质谱联用技术对8 个蛇龙珠营养系干红葡萄酒中50 种主要挥发性成分进行定性和定量检测,采用香气活性值（odor activity value,OAV）、单因素方差分析和主成分分析对测定数据进行处理分析。结果显示：在蛇龙珠干红葡萄酒中β-大马酮等24 种化合物OAV不小于1,对葡萄酒香气具有贡献。乙酸乙酯等12 种化合物可较好实现对8 个蛇龙珠营养系干红葡萄酒的判别分类,E-01、E-02、E-04、E-05营养系间存在明显差异,而E-06、E-07和E-08之间差异很小。结合感官品评结果发现,γ-壬内酯和里哪醇对提高蛇龙珠干红葡萄酒感官品质具有较大贡献,但含量需控制在一定范围内;而壬醛和4-乙基苯酚含量较高会显著降低葡萄酒感官品质,此外,β-大马酮、乙酸乙酯、癸酸乙酯等含量较高也会对葡萄酒的感官品质带来负面影响。蛇龙珠干红葡萄酒的香气特点不是由某个或某类香气成分产生的,是各种香气成分平衡作用的结果。     

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.     

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.     

Characterization of Volatile Flavor Compounds in Chinese Rice Wine Fermented from Enzymatic Extruded Rice

Enzymatic extrusion, instead of traditional steam cooking, to treat rice is an efficient and alternative pretreatment for Chinese rice wine fermentation. In order to determine the formation of volatiles in enzymatic extrusion‐processed rice wine (EE), and to confirm its characteristic flavor compounds, headspace solid‐phase micro‐extraction followed by GC–MS was used. A total of 66 volatile compounds were identified in EE. During fermentation, most volatiles generated from enzymatic extruded rice had the similar trends with those from steam‐cooked rice, but the differences in the concentration of volatiles indicated a changed balance of flavors release caused by enzymatic extrusion. Besides, the concentrations and sorts of volatiles in EEs fermented from different rice particle sizes, were not dramatically different. By principal component analysis, EE could be distinctly separated from other traditional Chinese rice wines according to its characteristic volatiles, namely, 2‐heptanol, 1‐octen‐3‐ol, ethyl 4‐hydroxybenzoate, methylpentyl 2‐propenoate, γ‐hexalactone, and 4‐vinylguaiacol.     

The impact of over‐maturation on the sensory and nutritional quality of Gouqi (Chinese wolfberry) wine

This study compared the nutritional quality and sensory attributes of wine made from dried Gouqi berries that were mature (NDG), mildly over‐matured (MDG) and severely over‐matured (SDG). Whilst these wines had the similar physicochemical properties, the MDG wine possessed higher polysaccharide levels, whereas the highest total flavonoids were found in the NDG wine. A slight difference in the amino acid composition was observed in these wines, whereas they exhibited the same biogenic amines composition. The MDG and SDG wines exhibited weaker fruity, floral and caramel aromas compared with the NDG wine. However, these wines showed similar chemical and fatty aromas. Sensory evaluation revealed that these wines could be distinguished by panelists, and the NDG wine was preferred by most tasters, followed by the MDG and SDG wines. These results suggest that the Gouqi wine made from mature berries exhibits the best nutritional and organoleptic quality. However, the over‐matured and severely over‐matured berries could also be useful for Gouqi berry wine production but with different nutritional and sensory properties. Copyright © 2017 The Institute of Brewing & Distilling