Use of unripe grapes harvested during cluster thinning as a method for reducing alcohol content and pH of wine

Background and Aims: Deep red full‐bodied wines can only be obtained from grapes with complete phenolic maturity, which frequently produce wines with high pH and alcohol content. The present study focuses on a new procedure for simultaneously reducing pH and ethanol content. Methods and Results: Grapes from cluster thinning were used to produce a very acidic low‐alcohol wine. The wine was treated with high doses of charcoal and bentonite. This odourless and colourless wine was used to reduce pH and ethanol content of wine produced from grapes, which had reached complete phenolic maturity. The anthocyanin and proanthocyanidin concentrations, the mean degree of polymerisation and the monomeric composition of proanthocyanidin of reduced‐alcohol wines were similar to those of their corresponding controls. Since the pH was lower, the colour of the reduced‐alcohol wines was more intense. No significant differences were found between reduced‐alcohol wines and their controls by triangle sensory tests using dark glasses for two of the three studied cultivars. Conclusion: The procedure described allowed production of wines with reduced alcohol content and pH, while retaining similar phenolic content and sensory properties. Significance of the Study: The proposed procedure is easy to apply, does not require specific equipment and offers a means of addressing the problem of wines developing high ethanol and low pH as a result of over‐ripening of grapes.     

Changes in volatile composition and sensory attributes of wines during alcohol content reduction

A desirable sensory profile is a major consumer driver for wine acceptability and should be considered during the production of reduced‐alcohol wines. Although various viticultural practices and microbiological approaches show promising results, separation technologies such as membrane filtration, in particular reverse osmosis and evaporative perstraction, in addition to vacuum distillation, represent the most common commercial methods used to produce reduced‐alcohol wine. However, ethanol removal from wine can result in a significant loss of volatile compounds such as esters (ethyl octanoate, ethyl acetate, isoamyl acetate) that contribute positively to the overall perceived aroma. These losses can potentially reduce the acceptability of the wine to consumers and decrease their willingness to purchase wines that have had their alcohol level reduced. The change in aroma as a result of the ethanol removal processes is influenced by a number of factors: the type of alcohol reduction process; the chemical‐physical properties (volatility, hydrophobicity, steric hindrance) of the aroma compounds; the retention properties of the wine non‐volatile matrix; and the ethanol level. This review identifies and summarises possible deleterious influences of the dealcoholisation process and describes best practice strategies to maintain the original wine composition. © 2016 Society of Chemical Industry     

自选酵母菌株草莓酒发酵特性比较

从草莓自然发酵液中分离筛选出酵母菌株D、E、H,以酿酒酵母A 为对照,采用气相色谱法分析不同酵母发酵草莓酒的主要香气成分,并通过降糖速率、产酒精能力、产酸量及感官质量评价,比较不同菌株的发酵特性。结果表明,菌株A 产酒精能力较强,菌株H 和菌株D 产香效果较好,菌株E 各项指标均较差。其中菌株H 发酵性能优良,还原糖含量可降至18.3g/L,酒精体积分数可达到12.92%,异丁醇、异戊醇、乳酸乙酯和β- 苯乙醇等香气成分均明显高于其他菌株,且酒体色泽澄清透亮,口味纯正,具有草莓酒的典型风味。     

Temporal Check‐All‐That‐Apply Characterization of Syrah Wine

Temporal Check‐All‐That‐Apply (TCATA) is a new dynamic sensory method for which analysis techniques are still being developed and optimized. In this study, TCATA methodology was applied for the evaluation of wine finish by trained panelists (n = 13) on Syrah wines with different ethanol concentrations (10.5% v/v and 15.5% v/v). Raw data were time standardized to create a percentage of finish duration, subsequently segmented into thirds (beginning, middle, and end) to capture panel perception. Results indicated the finish of the high ethanol treatments lasted longer (approximately 12 s longer) than the low ethanol treatment (P ≤ 0.05). Within each finish segment, Cochran's Q was conducted on each attribute and differences were detected amongst treatments (P ≤ 0.05). Pairwise tests showed the high ethanol treatments were more described by astringency, heat/ethanol burn, bitterness, dark fruit, and spices, whereas the low ethanol treatment was more characterized by sourness, red fruit, and green flavors (P ≤ 0.05). This study demonstrated techniques for dealing with the data generated by TCATA. Furthermore, this study further characterized the influence of ethanol on wine finish, and by extension wine quality, with implications to winemakers responsible for wine processing decisions involving alcohol management.     

果酒研究进展

果酒具有水果的天然香味,富含多种维生素和氨基酸,极具保健功能,适量饮用对心血管病、衰老引起的脑机能退化以及某些癌症有益,因此具有较高的研究价值。现代育种手段进行果酒酵母的选育方法有诱变育种、杂交育种、原生质体融合、基因克隆和转化等技术。对果酒香气成分的研究分析方法有直接注入法、静态顶隙气相色谱法、动态顶隙气相色谱法、高效液相色谱法、气相色谱一质谱联用法（GC／MS）等。从物理特征、化学特征、生物化学特征对果酒的稳定性进行研究。果酒酿造的新工艺、新技术有冷冻浓缩技术、果酒与啤酒工艺结合、蒸馏酒浸泡酒工艺与果酒发酵工艺相结合、固定化酵母技术、无醇果酒生产工艺等。采用PCR技术对发酵过程的特定菌进行检验和鉴定。     

The effects of ethanol and glycerol on the body and other sensory characteristics of Riesling wines

The effect of ethanol and glycerol concentration on the body, sweetness, acidity, aroma and flavour intensity, and perceived viscosity and hotness of three Riesling wines was assessed. The ethanol and glycerol contents of the wines were adjusted by addition to give three realistic levels (5.2, 7.2, 10.2 g/L glycerol and 11.6, 12.6 and 13.6 v/v ethanol). The nine treatment combinations (3 glycerol × 3 ethanol) were rated on the above attributes by a panel of trained tasters. Increased alcohol levels resulted in increased perceived hotness in all wines, and in higher body and perceived viscosity in two of the three wines. The effect of increasing glycerol content was less consistent with only one of each of the three wines showing increased viscosity and body. However, the mean viscosity ratings given to wines with 10 g/L glycerol was higher than at 5 g/L at all alcohol levels and for all wines, suggesting that differences in glycerol concentration typically displayed between dry white table wines can affect their perceived viscosity. Neither alcohol nor glycerol consistently affected sweetness, acidity, aroma or flavour intensity. Higher ratings of the abstract term 'body' were most commonly associated with higher ratings of flavour and/or perceived viscosity, suggesting that for the majority of tasters, these two attributes contributed to their interpretation of the term 'body'. Perceived hotness was not an important component of body, while the role of acidity in body perception was taster dependent.     

葡萄酒中香气物质研究进展

香气是葡萄酒感官评价的重要指标,也是影响葡萄酒质量风格和消费者导向的重要因素。各种风格特色的葡萄酒中具有的香气成分复杂多样,葡萄品种、发酵工艺、陈酿条件等因素均会影响其最终香气。保持品种典型性、提高发酵香气并改善陈酿风味一直是葡萄酒风味研究追求的目标,因此,全面分析葡萄酒中香气物质的形成途径和呈香机制至关重要。从发酵调控角度重点论述了品种和发酵香气成分的生成规律及酿造工艺对葡萄酒香气物质生成的调控机制,深入介绍相关风味酶和香气前体物质同香气物质的关系;探讨陈酿香气的生成路径并总结不同橡木制品和陈酿技术对葡萄酒陈酿香气特征的影响机理;简要阐述了香气物质的检测技术和香气物质间感知协同作用的研究方法,分析关键香气物质相互作用及基质效应对葡萄酒风味感知的影响。最后对未来研究方向和趋势提出展望,以期为建立以风味导向为基础的葡萄酒工艺调控手段提供理论依据和技术支持。     

The Production of Low-Alcohol Wines by Aerobic Yeasts

Aerobic yeasts of the genera Pichia and Williopis are commonly regarded as spoilage yeasts of beer and wine by causing turbidity, a surface film of yeast growth and often an excessive estery flavour. However, their ability to utilise sugars oxidatively for cell growth with the production of estery and other flavours of wine with only minimal production of ethanol suggests a method for the production of low-alcohol wines of pleasant “fermented” flavour without the need for additional equipment to remove alcohol by dialysis, reverse osmosis or distillation, or without the excessive sweetness remaining from arrested fermentation. Three strains of Pichia and one of Williopsis were examined for their ability to produce approximately 3%(v/v) ethanol and a good estery and fruity flavour. With normal anaerobic fermentation conditions, or with gentle stirring to prevent formation of a surface film, excessive amounts of alcohol were produced from grape juice of 15% or 20% (w/v) initial sugar concentration. However, an acceptably flavoured wine of alcohol content < 3% was produced by agitation and aeration during fermentation. The ethanol formed in the early stages of culture was oxidised to a final level < 3%, with the production of cell mass and an acceptable flavour.     

三种猕猴桃酒发酵过程中挥发性香气成分的变化

目的:分析不同的果实品种和发酵时间对猕猴桃发酵酒挥发性香气成分的影响。方法:采用顶空固相微萃取/气相色谱-质谱联用技术分析\     

Impact of chemical profile on sensory evaluation of tropical red wines

This study evaluated the correlation between the chemical composition of red wines and the sensory perception of the products. The visual, gustatory and flavour attributes of eight samples of tropical red wines were characterised by semi-trained panellists using the check-all-that-apply methodology. Titratable and volatile acidity, pH, contents of ethanol, total polyphenols and anthocyanins, and the chromatic parameters of the red wine samples were determined. The analysis of the correlations between visual attributes and sensory perception indicated that the evaluation of the wine colour attributes can predict other sensory characteristics related to aromas and flavours. This enabled the wine tasters to distinguish subtle variations in the visual attributes of the product. The results of this study indicated that panellists who underwent short-term training can sensorially perceive the influence of physicochemical variables on wine quality. Additionally, the correlation analysis enabled the identification of production adjustments and the understanding of the consumer perception of a complex product.     

乙醇传感器法测定葡萄酒和黄酒中乙醇的含量

建立了生物传感器法测定葡萄酒和黄酒中乙醇含量的分析方法。结果表明:乙醇含量在2~80μL/100mL浓度范围内线性关系良好,相关系数为0.9997;加标回收率(n=3)在99.22%~101.59%之间;精密度和重复性(n=4)的RSD%低于1%。与国标酒精计法测定结果对比,两种方法无显著差异。该法具有无需样品前处理、特异性好、灵敏度高、测定速度快等优点,适用于企业对发酵过程控制和产品的质量检测。      

Influence of pH and ethanol on malolactic fermentation and volatile aroma compound composition in white wines

The present study investigated the influences of pH and ethanol on malolactic fermentation (MLF) and the volatile aroma profile of the subsequent white wines from Riesling and Chardonnay inoculated with two different Oenococcus oeni strains. In all cases MLF was induced after completion of alcoholic fermentation (AF). Partial MLF occurred under low pH 3.2 and high alcohol (118.3 g/L) conditions. In the cases with complete MLF, the time required for each strain varied from 13 to 61 days and was dependent on bacterial culture, cultivar and wine parameter. Chemical properties of each wine were determined after AF, complete and partial MLF. The wines showed significant differences in total higher alcohols, esters and acids that are important for the sensory profile and quality of wine. This work demonstrated that the wine matrix as well as the pH and alcohol concentration affects MLF and the final volatile aroma profile. Results indicate that changes in volatile aroma composition are not necessarily related to complete MLF and that partial MLF already has distinct influences on the wine aroma profile of white wines.     

Membrane separation technology for the reduction of alcoholic degree of a white model wine

The reduction of the alcoholic degree of a white model wine by means of membrane separation technology was studied in this work. Reverse osmosis and nanofiltration are the most promising processes for the production of wines with low alcohol content, because they can operate at low temperature and thereby preserve the aromatic profile of wine. Assuming that the rejection of the main wine compounds (i.e. acids, sugars and tannins) is very high, the aim of this research was to study the permeation of several characteristic aroma compounds in the white model wine. Permeation was conducted in batch retentate-recycling mode with two reverse osmosis and one nanofiltration membranes previously conditioned with a 12 ml/100 ml aqueous ethanol solution. Aroma compounds were identified by gas chromatography coupled to quadrupolar mass selective spectrometry. A mathematical model allowed calculation of the aroma compound concentrations in the retentate and permeate streams as a function of permeate volume and the concentration of solutes in the diluted final wine at 8 ml/100 ml ethanol concentration.     

Wine is Bactericidal to Foodborne Pathogens

ABSTRACT: Red and white wines without added sulfite were tested for antibacterial activity against stationary-phase grown cells of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella Typhimurium, and Staphylococcus aureus . The wines had bactericidal activity against all strains, with the red wine being most potent. S . Typhimurium was most sensitive, with 6 log reduction after 10 min exposure to wine, whereas S. aureus appeared least sensitive to the wines. Mutants having the gene encoding the alternative sigma factor disrupted were generally more sensitive to wine than their wild-type counterparts. When different combinations of ethanol, organic acids, and acidity were tested against the pathogens, it was found that a composition of 0.15% malic acid, 0.6% tartaric acid, 15% ethanol, and pH 3.0 had a strong bactericidal effect. The compounds in the mixture seemed to act synergistically against the pathogens. The pathogens grew in 25% to 40% white wine diluted in brain hearth infusion broth, with S. aureus being able to grow at the highest concentration of wine. Preincubation of the bacteria in sublethal concentrations of wine and ethanol and pH 4.5 did not increase their tolerance against wine or against the mixture of organic acids and ethanol. In conclusion, wine had an antibacterial effect against the pathogens tested. The synergistic effect of organic acids, ethanol, and low pH seems to be responsible for a major part of the antibacterial effect of wine. The alternative sigma factors seemed to be involved in protection of the bacteria against wine.     

Exogenous Lipids and Ethanol Influences on the Foam Behavior of Sparkling Base Wines

The influence of added lipids (which mimic the endogeneous lipid pool of wine) on the foam behavior of sparkling base wines at various ethanol concentrations was investigated by measuring the foam expansion, foam stability and the Bikerman coefficient. Depending on their physical state, molecularly dissolved or aggregated, the lipids were only active at low alcohol concentration. At high alcochol content foam behavior was mainly governed by ethanol concentration. Bikerman coefficient variations were correlated with the surface tension variation.     

An assessment of the effects of wine volatiles on the perception of taste and astringency in wine

The objective of this work is measuring the effect of different volatile extract compositions on the perception of taste, astringency, global intensity and persistence of wine. Six Spanish wines, two from Chardonnay and four from Tempranillo grapes, all of them showing different chemical and sensory characteristics, were selected. Wines were separated into volatile and non-volatile fractions by solid phase extraction and lyophilisation and further liquid extraction, respectively. Eighteen “reconstituted wines” were prepared, combining different volatile extracts and different non-volatile matrices and adjusting ethanol content to 12% (v/v), and were further described by a specifically trained sensory panel. Taste attributes (sweetness, acidity, bitterness), astringency, aroma intensity, global intensity and persistence were assessed in both, original and “reconstituted” wines by using a numerical category scale. The sensory properties of the original wines were retained by their corresponding “reconstituted samples”. The sensory assessment of the “reconstituted wines” showed that the addition of volatile fruity extracts from white wines brought about a decrease in astringency and bitterness and an increase in sweet perception in all cases. While global intensity and persistence of white wine matrices were also increased, they did not change in red wine matrices, which suggests that the volatile fraction plays only a secondary role in these attributes of red wines. Similarly, the effects of replacing the volatile fraction of a red wine by volatile extracts from other red wines were small and inconsistent, which confirms that taste and astringency are primarily driven by non-volatile molecules in these wines.     

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.