Degradation of white wine haze proteins by Aspergillopepsin I and II during juice flash pasteurization

Bentonite is commonly used to remove grape proteins responsible for haze formation in white wines. Proteases potentially represent an alternative to bentonite, but so far none has shown satisfactory activity under winemaking conditions. A promising candidate is AGP, a mixture of Aspergillopepsins I and II.; a food grade, well characterized and inexpensive protease, active at wine pH and at high temperatures (60-80°C). AGP was added to two clarified grape juices with and without heat treatments (75°C, 1min) prior to fermentation. AGP showed some activity at fermentation temperatures (≈20% total protein reduction compared to control wine) and excellent activity when combined with juice heating (≈90% total protein reduction). The more heat stable grape proteins, i.e. those not contributing to wine hazing, were not affected by the treatments and therefore accounted for the remaining 10% of protein still in solution after the treatments. The main physicochemical parameters and sensorial characteristics of wines produced with AGP were not different from controls.     

Protein evolution during the early stages of white winemaking and its relations with wine stability

Background and Aims: Grape proteins are responsible for the appearance of haziness in white wines during storage after bottling. However, only a few studies have approached the analysis of the fate of must proteins throughout the alcoholic fermentation. This study aimed to systematically investigate the daily variations in protein type and content during the fermentation in order to understand its influence on hazing potential and to attain some basic information to improve the practical management of grape proteins involved in the hazing of white wines. Methods and Results: The evolution of total soluble protein and individual protein fractions was studied in samples taken before, during and after alcoholic fermentation of a white grape must. The results were then related to variations in protein instability as measured by the heat test. Both the quantity of soluble protein and the protein instability increased during fermentation and then decreased after 1‐month storage of the wine. Protein composition did not vary during fermentation as assessed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and anion exchange chromatography (AEC). However, variations in the relative proportions of the six protein fractions obtainable by AEC were noted in the different samples. The contribution of each AEC protein fraction to wine instability was determined by considering both the intrinsic instability and the relative quantity of each of the individual protein fractions in the wine. It was demonstrated that the grape thaumatin‐like protein VVTL1, as identified by mass spectrometry, showed the largest increase during fermentation and accounted for almost 40% of the heat‐induced haze of the final wine. Moreover, the decreased protein instability noted after one month storage of the wine could be attributed to the stabilizing effect of polysaccharides released by the yeast cells. Conclusions: The quantity and relative proportion of soluble proteins vary during and after the alcoholic fermentation, as does their heat instability in wine. Grape VVTL1, constituting a large proportion of the total proteins in wine, seems to play a major role in protein haze formation. The release of yeast polysaccharides is related to an increased heat stability of total wine protein, despite the increase in the relative proportion of their most unstable component VVTL1. Therefore, the hazing potential of a white wine seems to be affected by variations in the relative proportions of its macromolecular components occurring in the early stages of winemaking. Significance of the Study: This study addressed for the first time the issue of the protein changing during the fermentation of white wine. The results obtained here offer useful information to aid understanding of the contribution of individual proteins to white wine instability, which can be applied for the improvement of the winemaking process.     

Preventing protein haze in bottled white wine

Slow denaturation of wine proteins is thought to lead to protein aggregation, flocculation into a hazy suspension and formation of precipitates. The majority of wine proteins responsible for haze are grape‐derived, have low isoelectric points and molecular weight. They are grape pathogenesis‐related (PR) proteins that are expressed throughout the ripening period post véraison, and are highly resistant to low pH and enzymatic or non‐enzymatic proteolysis. Protein levels in un‐fined white wine differ by variety and range up to 300 mg/L. Infection with some common grapevine pathogens or skin contact, such as occurs during transport of mechanically harvested fruit, results in enhanced concentrations of some PR proteins in juice and wine. Oenological control of protein instability is achieved through adsorption of wine proteins onto bentonite. The adsorption of proteins onto bentonite occurs within several minutes, suggesting that a continuous contacting process could be developed. The addition of proteolytic enzyme during short term heat exposure, to induce PR protein denaturation, showed promise as an alternative to bentonite fining. The addition of haze‐protective factors, yeast mannoproteins, to wines results in decreased particle size of haze, probably by competition with wine proteins for other non‐proteinaceous wine components required for the formation of large insoluble aggregations of protein. Other wine components likely to influence haze formation are ethanol concentration, pH, metal ions and phenolic compounds.     

Protein stabilisation of white wines using zirconium dioxide enclosed in a metallic cage

Backgrounds and Aims: White wines are stabilised by removing the heat unstable proteins through adsorption by bentonite. Bentonite fining is not an efficient wine processing step and can also remove other wine components. Alternative absorbents are thus sought; zirconium dioxide (zirconia) is recognised as a promising candidate. The aim of this work was to assess the viability of zirconia treatments to stabilise white wines, with particular attention on process development. Methods and Results: Effective treatment was achieved by enclosing zirconia pellets into a metallic cage submerged in the wine. With this method, the wine could be treated with the adsorbent for the time required for protein stabilisation, and then removed without further manipulation. Zirconia treatments of three unstable wines partially or fully stabilised them without detectable modifications of their physicochemical parameters and colours, apart from the removal of metals and some acids, particularly when wines were treated for long times and with high dosages of the adsorbent. A simple and inexpensive zirconia regeneration method was also developed. Conclusions: The zirconia application to wine was very effective in removing proteins, and the proposed regeneration procedure could facilitate the uptake and development of zirconia‐based solutions for the wine industry. Significance of the Study: This study confirmed the effectiveness of zirconia in removing wine proteins and demonstrated that the proposed method of application has the potential to become a viable alternative to bentonite.     

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.     

苹果酸-乳酸发酵对葡萄酒中活性成分的影响

苹果酸-乳酸发酵是优质红葡萄酒酿造中必不可少的工艺之一,经过苹果酸-乳酸发酵,不但能有效降低葡萄酒的酸度,而且活性成分的含量或种类也会增加,从而提高葡萄酒对人体健康的正面影响。本文综述了经苹果酸-乳酸发酵的葡萄酒中氨基酸、益生菌、有机酸、多酚类物质、高级醇和酯类的变化,并简要介绍其抗癌、抗氧化、抗心血管疾病及抗菌消炎的功效,另外,还发现了一些活性成分如维生素、矿物质等在苹果酸-乳酸发酵前后的变化情况罕有报道,可作为进一步的研究方向。本文以期为研究利用中国野生葡萄种质资源、酿造优质中国野生葡萄酒提供参考。     

果胶酶对红葡萄酒主要成分的影响

以赤霞珠和蛇龙珠葡萄为原料，在葡萄破碎除梗后加入不同浓度的葡萄酒专用果胶酶，分析其对葡萄汁成分、葡萄酒发酵参数及原酒主要成分的影响。结果表明，加入果胶酶对葡萄汁的糖酸含量几乎无影响，但可降低汁液的粘度，利于色素的溶出，颜色较深；加入果胶酶的样品比未加果胶酶的样品发酵剧烈迅速，可降低挥发酸的生成量；可使原酒干浸出物含量和总酚含量增加，提高葡萄酒质量；残糖略有上升，但均在4g／L以下，不影响葡萄酒质量。     

Implications of nitrogen nutrition for grapes, fermentation and wine

This review discusses the impacts of nitrogen addition in the vineyard and winery, and establishes the effects that nitrogen has on grape berry and wine composition and the sensory attributes of wine. Nitrogen is the most abundant soil‐derived macronutrient in a grapevine, and plays a major role in many of the biological functions and processes of both grapevine and fermentative microorganisms. Manipulation of grapevine nitrogen nutrition has the potential to influence quality components in the grape and, ultimately, the wine. In addition, fermentation kinetics and formation of flavour‐active metabolites are also affected by the nitrogen status of the must, which can be further manipulated by addition of nitrogen in the winery. The only consistent effect of nitrogen application in the vineyard on grape berry quality components is an increase in the concentration of the major nitrogenous compounds, such as total nitrogen, total amino acids, arginine, proline and ammonium, and consequently yeast‐assimilable nitrogen (YAN). Both the form and amount of YAN have significant implications for wine quality. Low must YAN leads to low yeast populations and poor fermentation vigour, increased risk of sluggish/stuck/slow fermentations, increased production of undesirable thiols (e.g. hydrogen sulfide) and higher alcohols, and low production of esters and long chain volatile fatty acids. High must YAN leads to increased biomass and higher maximum heat output due to greater fermentation vigour, and increased formation of ethyl acetate, acetic acid and volatile acidity. Increased concentrations of haze‐causing proteins, urea and ethyl carbamate and biogenic amines are also associated with high YAN musts. The risk of microbial instability, potential taint from Botrytis‐infected fruit and possibly atypical ageing character is also increased. Intermediate must YAN favours the best balance between desirable and undesirable chemical and sensory wine attributes. ‘Macro tuning’, of berry nitrogen status can be achieved in the vineyard, given genetic constraints, but the final ‘micro tuning’ can be more readily achieved in the winery by the use of nitrogen supplements, such as diammonium phosphate (DAP) and the choice of fermentation conditions. This point highlights the need to monitor nitrogen not only in the vineyard but also in the must immediately before fermentation, so that appropriate additions can be made when required. Overall, optimisation of vineyard and fermentation nitrogen can contribute to quality factors in wine and hence affect its value. However, a better understanding of the effect of nitrogen on grape secondary metabolites and different types of nitrogen sources on yeast flavour metabolism and wine sensory properties is still required.     

发展冰酒要走科学规范化之路

冰酒是葡萄酒家族中的高贵品种,具有独特的果香、口味和色泽。冰酒的生产对原料的品种、质量和发酵贮存条件都有严格要求。我国的冰酒生产还处于发展阶段,并显示了无限的商机。目前冰酒生产仍然存在原料不符合规范要求、采用人工冷冻处理原料、补加糖分和用浓缩葡萄汁稀释等弊端。因此,应规范生产,加强监管,制定冰酒标准,实施原产地域保护等措施;为冰酒发展提供一个良好的发展环境。（孙悟）     

酶膜分离法果汁澄清工艺

运用果胶酶，淀粉酶等澄清剂，结合膜分离技术，分析得出适合沙棘，柠檬汁，梨汁，猕猴桃汁，葡萄汁，梨汁，猕猴桃汁，葡萄汁，山渣汁，枣汁等果汁的澄清工艺。能有效去除果汁饮料中的果胶，蛋白和高级棕榈酸酯絮状物等造成沉淀的物质。     

玛卡发酵型葡萄酒的酿造工艺研究

以玛卡和赤霞珠葡萄为主要发酵原料,通过酿酒酵母SC203进行发酵生产出具有保健功能的玛卡发酵型葡萄酒。在单因素试验基础上结合正交试验对玛卡发酵型葡萄酒酿造工艺进行优化研究,确定发酵工艺最佳条件为发酵温度30 ℃、玛卡粉添加量4%、SO2添加量90 mg/L,并添加壳聚糖0.05%进行澄清,在此最优条件下研制的玛卡发酵型葡萄酒感官评分为95分,酒精度为12.4%vol,酒体澄清有光泽,具有独特玛卡的风味。     

沙糖桔葡萄复合果酒酿造工艺研究

以沙糖桔、巨峰葡萄为原料,研究其混合发酵工艺对复合果酒的苦味以及澄清度的影响,采用单因素及正交试验对复合果酒的酿造工艺进行优化。结果表明,复合果酒最佳砂糖桔汁和葡萄汁添加量分别为40%和60%;最佳发酵工艺参数为酵母接种量为0.1 g/kg,初始糖度为24 °Bx,发酵温度24 ℃,主发酵时间为8 d。在此最佳发酵工艺条件下,复合果酒感官评分为82.8分,酒精度为11.88%vol。最佳脱苦工艺为柚苷酶添加量0.03%,酶解温度50 ℃,酶解时间为90 min。在此最佳脱苦工艺条件下,复合果酒感官评分为7.5分。加入0.06%的果胶酶和0.02%聚乙烯聚吡咯烷酮（PVPP）时,透光率为90.6%。沙糖桔葡萄复合果酒酒体清澈透亮、色泽诱人,口感柔和、爽口,香气浓郁。     

桃红葡萄酒酿造工艺优化研究

研究利用浸渍巨峰葡萄果浆酿制桃红葡萄酒。分析果浆处理和工艺对桃红葡萄酒品质的影响。结果表明,控制果浆色度在2.5~3.0作浸渍过程终点,浸渍结束后分离不超过30%果浆量,调整含糖量为26%并加入酵母进行主发酵。按常规经后发酵、澄清、过滤与检测合格后酿造出桃红色、清亮透明、怡悦和谐的果香与酒香并具有恰当收敛性与酒体完整的桃红葡萄酒。     

前体氨基酸对赤霞珠干红葡萄酒中生物胺含量的影响

以新疆地产赤霞珠果实为原料,在葡萄汁中分别加入不同浓度的7种前体氨基酸,进行酒精发酵与苹果酸-乳酸发酵。通过高效液相色谱法的分析检测,了解前体氨基酸对葡萄酒中8种生物胺含量的影响。结果表明,前体氨基酸对葡萄酒中生物胺的含量产生一定的影响,当加入质量浓度为40 mg/L和100 mg/L的组氨酸时,组胺含量由1.04 mg/L减少为0.20 mg/L和0.35 mg/L;而当加入色氨酸、精氨酸和鸟氨酸时,会使色胺和腐胺的含量有所降低,当加入300 mg/L质量浓度的精氨酸时,腐胺含量由1.45 mg/L减少至0.63 mg/L。当葡萄酒中加入同一种氨基酸时,对葡萄酒中不同的生物胺含量的影响也不尽相同。     

Effect of the Prefermentative Addition of Five Enological Tannins on Anthocyanins and Color in Red Wines

Abstract: The effects of prefermentation addition of 5 exogenous tannins with different‐origin anthocyanins and color characteristics were investigated in “Cabernet Sauvignon wines” at the end of alcoholic fermentation and the end of malolactic fermentation, and after 6 mo and 9 mo of bottle aging, respectively. The results showed that the application of GSKT2 could significantly retard the degradation of most anthocyanins in the process of alcoholic fermentation and the decrease of some pyranoanthocyanins during the subsequent 3 stages, thus causing more yellowness of wine in comparison with the control. Three other condensed tannins, GSKT1, QUET, and GSET, had a positive impact only on several anthocyanin components. Four condensed tannins all contributed to more redness, suggesting that the action mechanism might be to protect wine against oxidation or contribute to form copigmented anthocyanidins, or polymeric pigments. The application of FOLT (hydrolysable tannin) did not produce any influence on wine redness even after 9 mo of bottle aging. This work provides some reasons for the reasonable application of tannin additives. Practical Application: The prefermentative application of condensed tannins overall could protect some pigment components from degradation and enhance wine redness. Tannin additives with different origins have different effectiveness. The tannin additive obtained from grape skins, like GSKT2, could produce significant promotion on both redness and yellowness in wine. The prefermentation addition of hydroxylase tannin like FOLT seems not to have a significant effect on wine color.     

Effects of the proteins of indica rice and indica waxy rice on the formation of volatiles of sweet rice wine

The proteins in the raw materials affect the formation of flavour during fermentation. Among all the fermentation broth of protein fraction in the study, the rice prolamin and albumin effectively promoted floral, honey and fruity characteristics in fermentation with higher level of β-phenylethyl alcohol, 2,4-dimethyl-benzaldehyde and ethyl hexadecanoate than those in the fermentation of globulin and glutelin; albumin is with higher level of higher alcohols, but higher alcohols are not good for health because of their acute toxicity and neurotoxic effects. In a further fermentation experiment of addition of prolamin, extra prolamin significantly promoted the formation of aroma volatiles, especially medium and long fatty acid esters and β-phenylethyl alcohol and its acetate, and the content of β-phenethyl acetate in sweet rice wine with added prolamin was more than twice that of single sweet rice wine. This study demonstrates that the different rice protein components significantly affect the volatiles generated by microorganism metabolism to impact the flavour of sweet rice wine, and the flavour quality of sweet rice wine can be enhanced by increasing the prolamin content.     

The Effect of Proanthocyanidins on Growth and Alcoholic Fermentation of Wine Yeast under Copper Stress

Proanthocyanidins (PAs) derived from the grape skin, as well as from grape seeds, grape stems, are an important group of polyphenols in wine. The aim of this study was to understand the effect of PAs (0.1, 1.0 g/L) on growth and alcoholic fermentation of 2 strains of Saccharomyces cerevisiae (commercial strain FREDDO and newly selected strain BH8) during copper‐stress fermentation, using a simple model fermentation system. Our results showed that both PAs and Cu²⁺ could pose significant inhibition effects on the growth of yeast cells, CO₂ release, sugar consumption, and ethanol production during the initial phase of the fermentation. Compared to PAs, Cu²⁺ performed more obvious inhibition on the yeast growth and fermentation. However, adding 1.0 g/L PAs increased in the vitality and metabolism activity of yeast cells at the mid‐exponential phase of fermentation in the mediums with no copper and 0.1 mM Cu²⁺ added, shortened the period of wine fermentation, and decreased the copper residues. It indicated that PAs could improve the ability of wine yeast to resist detrimental effects under copper‐stress fermentation condition, maintaining cells metabolic activity, and fermentation could be controlled by manipulating PAs supplementation.     

红提和糯米复合发酵葡萄酒工艺优化及香气成分分析

目的：通过添加天然外源糖提升鲜食葡萄酒品质。方法：以红提为原料,糯米糖化液为外源糖,进行复合发酵红提葡萄酒工艺优化并分析鉴定葡萄酒中香气成分。以发酵温度、糯米糖化液和红提体积比、酵母接种量、SO2添加量为单因素,以乙醇体积分数和花色苷为指标研究红提葡萄酒发酵工艺;在单因素试验基础上进行3因素3水平响应面试验优化最佳发酵工艺。结果：单因素试验表明SO2添加量80?mg/L、发酵温度20?℃、酵母菌接种量1?g/L、糯米糖化液和红提体积比1∶4为最适发酵条件;响应面法优化红提果酒最佳发酵工艺为发酵温度21?℃、酵母接种量1.2?g/L、SO2添加量84?mg/L、体积比1∶4,发酵7?d得到体积分数为12.7%的红提葡萄酒。气相色谱-质谱联用仪共鉴定出39?种挥发性化合物,其中醇类15?种、酯类15?种、酸类5?种、萜类2?种。香气活性值（odor activity value,OAV）分析表明,共有12 种香气物质的OAV较高,主要为β-大马士酮、己酸乙酯、辛酸乙酯、乙酸异戊酯、癸酸乙酯。结论：以糯米糖化液为外源糖,可提升红提葡萄酒的乙醇体积分数,同时该葡萄酒具备良好的口感及典型的葡萄酒风味。     

Aroma release of a model wine solution as influenced by the presence of non-volatile components. Effect of commercial tannin extracts, polysaccharides and artificial saliva

The effect of commercial tannin extracts, extracted either from grape seeds or grape skins, a natural wine polysaccharide extract, pectin and arabinogalactan on the headspace release of selected aroma compounds from a “model wine” solution was investigated. Changes in the volatility of the aroma compounds were studied using headspace solid-phase microextraction combined with GC/FID. The performance of four commercially available fibre coatings was checked and the 50/30 ??m DVB/CAR/PDMS one was proved to be the most effective. A short sampling time (1 min) was used to determine the “true” headspace concentration at equilibrium between the headspace and the sample. In general, the volatility of the studied aroma compounds appeared to be correlated to increasing tannin levels as well as to their origin. The volatility of esters was generally increased upon tannin addition at low concentrations, while at higher addition levels the two extracts exhibited dissimilar behaviour attributed to their different composition. Both arabinogalactan and pectin addition at low concentrations increased the volatility of the studied aroma compounds, while at higher concentrations pectin exhibited a different behaviour by salting out hydrophobic compounds in the vapour phase. In addition, grape skin and seed tannin extracts in admixture with polysaccharides either prevented the macromolecular chains to associate with volatile molecules or led to additional flavour retention depending on the aroma compound and the addition level. Saliva addition enhanced the volatility of the most hydrophobic compounds whereas the hydrophilic compounds were retained into the matrix.     

下胶材料对低醇葡萄酒质量的影响

以牛血清蛋白、明胶及皂土为下胶材料,对赤霞珠和佳丽酿为原料酿造的低醇葡萄酒进行下胶实验。结果表明,牛血清蛋白澄清效果最不明显,加入量超过0．05g/L时可使酒中的蛋白质含量和总酚含量增加,吸光值稍微降低；加入明胶和皂土后,葡萄酒的澄清速度较快,蛋白质和总酚含量及吸光值均降低,且随着加入量的增加,降低幅度逐渐增大。三种下胶材料中,皂土的澄清效果最明显,但使酒的口味变淡,颜色变浅,在生产上应慎用；明胶可以优先考虑,因为它的澄清效果较好,颜色变化较小,但易下胶过量,应结合单宁一起使用,效果更佳。