Loss and formation of malodorous volatile sulfhydryl compounds during wine storage

Volatile sulfur compounds (VSCs), particularly low molecular weight sulfhydryls like hydrogen sulfide (H₂S) and methanethiol (MeSH), are often observed in wines with sulfurous off-aromas. Recent work has shown both H₂S and MeSH can increase up to a few µM (> 40 µg/L) during anoxic storage, but the identity of the latent sources of these sulfhydryls is still disputed. This review critically evaluates the latent precursors and pathways likely to be responsible for the loss and formation of these sulfhydryls during wine storage based on the existing enology literature as well as studies from food chemistry, geochemistry, biochemistry, and synthetic chemistry. We propose that three precursor classes have sufficient concentration and metastability to serve as latent sulfhydryl precursors in wine: 1) transition metal-sulfhydryl complexes, particularly those formed following Cu(II) addition, which are released under anoxic conditions through an unknown mechanism; 2) asymmetric disulfides, polysulfanes, and (di)organopolysulfanes formed through transition-metal mediated oxidation (e.g., Cu(II)) of sulfhydryls or pesticide degradation, and released through sulfitolysis, metal-catalyzed thiol-disulfide exchange or related reactions; 3) S-alkylthioacetates, primarily formed during fermentation, and releasable hydrolytically. Some evidence also exists for S-amino acids serving as precursors. Based on these findings, we propose a “decision tree” approach to choosing appropriate strategies for managing wines with sulfurous off-aromas.     

Changes in phenolic composition and antioxidant activity of white wine during bottle storage: Accelerated browning test versus bottle storage

Polyphenol content, antioxidant activity, reducing power, colour and changes during storage over nine months in bottles and after accelerated browning were studied in selected Hellenic varietal white wines. The following phenolic compounds were identified in the wines: Caftaric, coutaric, fertaric, ferulic, caffeic, p-coumaric and gallic acids, (+)-catechin and (−)-epicatechin. The results showed that the contents of most of the phenols diminished with time, with the exception of caffeic, ferulic and p-coumaric acids. Antioxidant activity increased with storage whereas reducing power remained significantly unaffected. Accelerated browning did not significantly alter the concentrations of tartaric acid esters but it increased the concentrations of the hydroxycinnamic and gallic acids. (+)-Catechin concentration was not affected while (−)-epicatechin decreased. Antioxidant activity did not show any significant change but reducing power was reduced after the end of the browning test. As for the absorbance at 420 nm, it remained unchanged during storage, but it was significantly increased after accelerated browning.     

干白葡萄酒瓶储过程香气物质变化及其与感官品质演变的相关性

为探究不同酿酒单宁对葡萄酒颜色和花色苷含量的影响,以赤霞珠葡萄为原料,使用五种不同的酿酒单宁进行葡萄酒酿造及120 d的陈酿。在发酵完成以及陈酿过程中对葡萄酒总酚、总花色苷、总黄烷醇、单体花色苷含量、色度以及感官评价进行分析。结果表明,酒精发酵前添加单宁可以提高葡萄酒总酚含量、影响葡萄酒颜色以及提高葡萄酒感官品质。BSO组（橡木单宁）总酚含量的提升最明显,最高峰值达到1850.13 mg/L。陈酿120 d后,BRE组（绿茶单宁）b^*（黄色调）明显高于其他实验组,颜色偏黄褐色。陈酿120 d后,PTZ组（葡萄籽单宁）和ECA组（栗木单宁）a^*（红色调）比陈酿后的对照组（不使用单宁）分别提升了38.19%、27.76%,颜色更加稳定,颜色偏紫红色调。由相关性共线网络分析可知,葡萄酒的红色与大多数单体花色苷呈正相关（P<0.05,|r|>0.6）,与部分乙酰化花色（乙酰化二甲基花翠素-3-O-葡萄糖苷、花翠素-3-O-乙酰化葡萄糖苷、香豆酰化3'-甲基花翠素-3-O-葡萄糖苷）呈负相关（P<0.05,|r|>0.6）。综上所述,发酵前添加酿酒单宁更有利于提高红葡萄酒的品质,来自葡萄籽的缩合单宁具有最优质的辅色效果。

     

PET瓶储条件对蓝莓酒颜色和酚类物质含量的影响

以在聚对苯甲酸乙二醇酯(polyethylene terephthalate,PET)瓶内贮存的发酵结束后的蓝莓酒为研究对象,探究不同储存条件对其酚类物质和颜色的影响。结果表明:与室温有光和室温避光条件相比,酒窖储存的酒样,总酚和总花色苷含量下降速度较慢,且对游离花色苷的降解和聚合花色苷的上升有更好的抑制效果,保护了蓝莓酒的红色色调,减缓了酒颜色向砖红色转变的速度。相关性分析发现,酚类物质影响酒样的颜色参数,总酚、总花色苷、游离花色苷及辅色花色苷与红色色调显著正相关,总类黄酮及聚合花色苷与黄色色调显著正相关。主成分分析结果显示,酒窖储存酒样的品质与其他两种条件有显著差异;在瓶储6个月内,室温避光和室温有光组酒样之间差异不显著(p<0.05),说明温度是决定蓝莓酒PET瓶储期内酚类物质和颜色参数的因素。      

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.     

罐罐肉加工与贮藏过程中挥发性物质变化的研究

为了探明雅安罐罐肉挥发性物质的变化规律,本研究以不同加工与贮藏阶段的罐罐肉为对象,用同时蒸馏萃取结合气相色谱/质谱法对挥发性化合物进行分析。结果显示,罐罐肉在加工与贮藏过程中共检测出120种挥发性物质,醇、醛、酮、烃、酰胺、酯是主要成分,其中以己醛和2,4-癸二烯醛为主的醛类物质相对含量最高（最高达64.42%）。在加工过程中醛、酮、酯显著增加,并检测出酰胺类物质。在贮藏过程中醇、醛、酮的相对含量整体呈现下降趋势,烃类、酰胺类、酯类和其他化合物的相对含量整体呈上升趋势,并新产生了（2E）-2-十一碳烯醛、甲酸己酯、（Z）-9-十八烯酸酰胺和2-戊基呋喃等物质。      

Binding of oak volatile compounds by wine lees during simulation of wine ageing

The retention of wine volatile compounds by wine lees could have an influence on the quality of the product. The aim of this work was to study the binding of wine volatile compounds from oak wood by the wine lees during simulation of wine ageing. The compounds with the most affinity for the lees were eugenol, 4-propylguaiacol, 4-methylguaiacol, furfural and 5-methylfurfural. Lees also bound other compounds important for aroma in aged wine such as oak lactones, although to a lesser degree. Guaiacol and γ-nonalactone were the only compounds studied that were not bound by the lees. Because the lees bind important compounds to wine aroma, ageing red wine in oak barrel in presence of lees could diminish the impact of the aromatic compounds from oak wood on wine aroma.     

瓶装黄酒杀菌条件与风味关系研究

对瓶装黄酒杀菌温度、时间等对酒质、风味的影响作了系统的研究和分析。实验表明：杀菌温度在60℃-65℃，随杀菌时间延长酒质得到改善；当杀菌温度超过70℃时，杀菌时间应控制在1h以内；当75℃时杀菌超过30min，黄酒风味有下降的趋势；80％以上，黄酒风味随杀菌时间延长而变劣。     

刺葡萄利口酒的香气轮廊及其在瓶储过程的变化

采用顶空固相微萃取(HS-SPME)与气相色谱-质谱联用(GC-MS)技术分析了刺葡萄利口基酒、蒸馏酒(强化酒精)及两者调配而成的4个不同酒精度的刺葡萄利口酒中的香气物质,并跟踪其在瓶储过程中的变化。结果表明,刺葡萄利口基酒和蒸馏酒中的香气物质均以酯类和醇类为主,且大部分物质的含量在后者中均显著高于前者(P<0.05)。在刺葡萄利口酒中共检测到48种香气物质,主要包括酯类、醇类和酸类,且大部分物质的含量随酒精度增加而升高。根据香气组分的气味活性值(OAV)判断,乙酸乙酯、丁酸乙酯、己酸乙酯等13种物质是刺葡萄利口酒的主要呈香组分。K-means聚类分析结果表明,多数醇类和酯类物质的含量在瓶储期间逐渐下降,而挥发性酸类物质的含量逐渐上升。瓶储期间原来较强的果香气味逐渐减弱,而原来较弱的薰衣草气味逐渐增强。     

刺葡萄利口酒的香气轮廊及其在瓶储过程的变化

采用顶空固相微萃取（HS-SPME）与气相色谱-质谱联用（GC-MS）技术分析了刺葡萄利口基酒、蒸馏酒（强化酒精）及两者调配而成的4个不同酒精度的刺葡萄利口酒中的香气物质,并跟踪其在瓶储过程中的变化。结果表明,刺葡萄利口基酒和蒸馏酒中的香气物质均以酯类和醇类为主,且大部分物质的含量在后者中均显著高于前者（P＜0.05）。在刺葡萄利口酒中共检测到48种香气物质,主要包括酯类、醇类和酸类,且大部分物质的含量随酒精度增加而升高。根据香气组分的气味活性值（OAV）判断,乙酸乙酯、丁酸乙酯、己酸乙酯等13种物质是刺葡萄利口酒的主要呈香组分。K-means聚类分析结果表明,多数醇类和酯类物质的含量在瓶储期间逐渐下降,而挥发性酸类物质的含量逐渐上升。瓶储期间原来较强的果香气味逐渐减弱,而原来较弱的薰衣草气味逐渐增强。     

Evolution of volatile compounds in papaya wine fermented with three Williopsis saturnus yeasts

The changes in volatile compounds during papaya juice fermentation with three Williopsis saturnus yeasts were investigated in this study. Time‐course papaya juice fermentations were carried out using three Williopsis saturnus yeasts: W. saturnus var. mrakii NCYC2251, W. saturnus var. saturnus NCYC22 and W. saturnus var. sargentensis NCYC2727. Changes in yeast cell population, Brix and pH were similar among the three yeasts, which preferentially utilised glucose over fructose while partially degrading l ‐malic acid. A range of volatile compounds were produced during fermentation including fatty acids, alcohols and esters with esters being the most abundant volatile compounds produced. Benzyl isothiocyanate, butyric acid, 2‐ethylhexanol, benzaldehyde and β‐damascenone present in the papaya juice were metabolised to trace levels during fermentation. There were significant variations among the three yeasts in their ability to produce and metabolise volatile compounds during fermentation. The study suggests that papaya juice fermentation with W. saturnus yeasts is able to result in the formation of a more complex aroma compounds.     

Chemistry of copper in white wine: a review

Copper is one element in wine that has considerable notoriety. While current winemaking practice tends to minimise the amount of copper that results from vineyard and winery sources, the addition of copper(II), either as its sulfate or citrate, to remove sulfidic off‐odours may result in an elevated concentration in the finished (bottled) wine. Residual copper in white wine has been linked to oxidative and reductive spoilage processes, although the mechanisms are at times speculative. The presence of copper has been implicated in haze formation (copper casse) and linked to protein instability. More recent concerns include the coexistence of residual copper and hydrogen sulfide in wine stored under low oxygen conditions. The chemistry of copper is important in both white and red wine. While there are some overlapping issues, especially with respect to sulfidic off‐odours, both white and red wine display their own unique chemistry. Thus, this review describes the state of knowledge of copper in white wine, differentiating between evidence‐based claims and speculation. It also identifies areas of research that will provide a much clearer understanding of the role of copper in wine spoilage.     

低温储藏条件下氧化状态对牦牛肝中挥发性化合物的影响

为了研究低温储藏条件下氧化状态对牦牛肝中挥发性化合物的影响,选取成年牦牛肝为研究对象,在低温条件下进行储藏,测定储藏前后的过氧化氢值（POV）、硫代苯巴比妥酸反应底物值（TBARS）以及挥发性化合物。结果表明,相比于储藏前,储藏后的POV和TBARS分别增加了135.96%和197.28%。储藏前后共检出31种挥发性化合物,其中苯乙醛、反-2-癸烯醛、2-庚酮等10种物质仅在储藏后检出。经储藏后,醛类物质含量增加了17.38%,其中己醛、庚醛、辛醛3种直链脂肪醛分别增加了8.95%、3.42%、1.17%,而异戊醛减少了1.58%。经过储藏酮类减少了10.40%,丙酮下降了12.45%,而2-丁酮、2-庚酮等甲基酮含量均提高。杂环类化合物在储藏前后差异不显著,但苯并噻唑却极显著地降低了1.71%（p<0.01）。结果表明,在低温储藏条件下氧化程度的升高,增加了直链脂肪醛和甲基酮等脂质氧化产物,而减少了异戊醛、苯并噻唑等美拉德反应产物。      

Foam aptitude of Bobal variety in white sparkling wine elaboration and study of volatile compounds

Fining agents can also have an effect on the flavor components of the must, and other compounds which are important for the sensory characteristics and in the case of sparkling wine, the foam quality. The influence of fining agents and tirage solution, on volatile compounds, and foam characteristics of sparkling wines made from grapes of the Bobal variety was studied. The data obtained show how the fining agent affects the foam properties and the final volatile composition of sparkling wines. In this study, it was bentonite with gelatine that produced amounts of acetates and esters. The use of Colle 2P in the tirage solution means that more aromatic sparkling wines with better foam characteristics can be obtained.     

Effect of storage on the phenolic content,volatile composition and colour of white wines from the varieties Zalema and Colombard

Different quality attributes and chemical components of wines change during storage as a function of a series of factors. Thus, in young white wines, changes in phenolics, that lead to modifications of their colour as a result of oxidation processes, are well-known. These reactions can also alter their volatile profile giving rise to the appearance of new aromas, which in some cases are undesirable. In this study we have carried out a thorough evaluation of the changes in the colour, volatiles and phenolics of Zalema and Colombard wines during 1 year of storage under different conditions of temperature and position. The phenolics and colour were more affected than was the volatiles profile and wines kept in the cold could be clearly distinguished from the others, whilst the position of the bottles onlt slightly affected the wines during storage. Results showed that the blending of Zalema wines with Colombard wines may be an appropriate means of enhancing the acidity of the former without dramatically affecting its character.     

The role of light,temperature and wine bottle colour on pigment enhancement in white wine

Pigmentation enhancement in a Chardonnay wine with high flavan-3-ol concentration was examined by irradiating the wine under controlled conditions. Heating the wine in darkness required temperatures in excess of 50 °C before enhanced pigmentation became apparent. It was found that ultraviolet and, to a lesser extent, low wavelength visible light contributed to pigment production. The development of pigmentation depended on wine bottle glass colour: Flint > Arctic Blue > French Green > Antique Green. This is in agreement with the transmission characteristics of the bottles with even the darkest (Antique Green) allowing the transmission of some ultraviolet light. Riboflavin, when added to the wine, degraded rapidly when exposed to radiation <400 nm. The degradation of riboflavin and the onset of colour development depended on the actual amounts as well as the ratio of riboflavin to flavan-3-ol, suggesting that a complex series of reactions are occurring. A degradation product of riboflavin may be contributing to the increase in absorbance in the visible region observed during light exposure.     

干型黄酒贮存过程中品质变化的初探

新酒经贮存一段时间品质明显改变,通过比色法、气相色谱及感官品尝对湖州干型黄酒当年新酒和贮存1～5年陈酒的颜色、主要芳香性成分及口感等品质因素进行测试比较.结果表明,黄酒在贮存老熟过程中氨基、羰基缓慢反应,酒体颜色逐渐加深,随着贮存期延长,黄酒中主要芳香性成分互相转化,酯含量增加,醇含量减少,最后达到一种平衡,得到香气浓郁、醇和爽适的黄酒.通过对黄酒贮存老熟过程中色、香、味等品质因素变化规律及对产生变化的原因进行初步分析和探讨,提出一个陈化因子--微氧含量,同时为黄酒贮存提出一些科学的建议.