壳聚糖树脂对玫瑰香白葡萄酒稳定性的作用

以壳聚糖、皂土、硝酸铈铵为主要原料,采用反相悬浮交联法制备了壳聚糖树脂(CM)、壳聚糖包埋皂土微球(CMB)、壳聚糖铈树脂(RCCM),比较3种树脂以及皂土对玫瑰香白葡萄酒稳定性效果。实验表明,静态稳定处理的最佳条件为:树脂使用量为20.0 g/L,皂土悬浮液使用量为0.30 g/L,温度15.0℃,磁力搅拌48 h,浊度差都稳定在0.50EBC以下,此时的葡萄酒比较稳定。3种树脂稳定效果比皂土好,主要表现在澄清速度快,对蛋白和多酚具有较强的吸附,对Cu2+的吸附比对Fe2+的吸附效果显著,特征有机酸影响不显著。动态处理比静态处理效果好。动态处理中,用CM-Column处理的效果较好。实验表明,CM为最佳的澄清剂,最佳澄清方式为CM-Column澄清。     

白葡萄酒蛋白质稳定的新展望--酶解法

白葡萄酒易出现蛋白质沉淀，而传统除去蛋白质的方法无非是在葡萄酒中加入明胶或膨润土将葡萄酒中的蛋白质除掉。当然这是保持了葡萄酒的稳定性，但另一方面将葡萄酒中稳定性蛋白质也除掉了，这就降低了葡萄酒的营养价值。使用蛋白质酶解法可将葡萄酒中蛋白质水解成小肽，这样既可使得葡萄酒具有很好的稳定性，又可以提高葡萄酒的营养价值。     

酶法提高白葡萄酒质量稳定性的研究

利用木瓜蛋白酶水解白葡萄酒中非稳定蛋白,通过大量试验,确定了酶反应最佳条件为：加酶量为0．6％（w／v）,酶反应pH6．5,在45℃反应38h。此条件下,白葡萄酒中的蛋白含量降低为0．31g／L,氨基酸含量升高至6．7mg／L。     

壳聚糖在白葡萄酒澄清中的应用研究

研究了壳聚糖在白葡萄酒澄清处理中的作用机理、应用条件、作用剂量及澄清效果，壳聚糖的应用有效地提高了白葡萄酒的澄清度、稳定性及光学效果。实验证明，壳聚糖对白葡萄酒的澄清作用效果明显优于明胶、皂土等常用的葡萄酒澄清剂。     

壳聚糖、皂土澄清剂对发酵酒澄清作用的研究

对壳聚糖、皂土对刺梨发酵酒的澄清作用进行了研究，结果表明：壳聚糖、皂土澄清效果优于明胶、果胶酶，其中壳聚糖澄清效果最佳，产品风味、品质好。实验还发现，壳聚糖、皂土联用，效果优于单一澄清剂，澄清后酒体清亮透明、风味好、具有良好的贮藏稳定性。     

皂土和壳聚糖对青梅发酵酒澄清效果的比较研究

研究了皂土和壳聚糖对青梅发酵酒的澄清效果,并通过正交试验及综合评比分析,结果表明壳聚糖的澄清效果明显好于皂土,经壳聚糖处理的青梅发酵酒透光率达98.5%,确定了最佳澄清工艺条件：壳聚糖用量0.5g/L,pH为3.2,温度26℃,澄清时间24h。澄清后的发酵酒澄清透明,稳定性增加。     

壳聚糖、皂土对枸杞酒澄清效果和稳定作用研究

通过正交试验确定了壳聚糖、皂土混合使用的最优澄清条件,即壳聚糖添加量4 %,皂土添加量0.15 %,澄清时间2.5 h.以此条件对枸杞酒作澄清处理,其透光率可达98.26 %,降酚、降蛋白率分别达到96.44 %和85.2 %.同时,枸杞酒中的蛋白质、酒石酸氢钾、铁、铜以及氧化稳定性试验结果均呈阴性,表明壳聚糖、皂土混合澄清剂对枸杞酒具有较好的澄清效果和稳定作用,并优于壳聚糖或皂土单独使用.     

菠萝蛋白酶对干白葡萄酒蛋白质稳定性的影响

研究菠萝蛋白酶对干白葡萄酒蛋白质稳定性的影响,以新鲜干白葡萄酒为试验材料,添加菠萝蛋白酶,通过测定葡萄酒的浊度、蛋白质稳定性、蛋白质含量,确定其最适添加量、作用温度和作用时间。结果表明,菠萝蛋白酶对两款酒样澄清的最佳添加量分别为2.0 mg/L、2.5 mg/L,温度均为22 ℃,作用时间为24 h。菠萝蛋白酶可澄清干白葡萄酒,明显提高其蛋白质稳定性。     

白葡萄酒中不稳定蛋白的研究进展

白葡萄酒中的蛋白质不稳定是仅次于酒石酸不稳定的问题。主要阐述了白葡萄酒中不稳定蛋白的来源,蛋白质对白葡萄酒的影响及不稳定蛋白检测的方法;总结了近年来提高白葡萄酒中蛋白稳定的方法,并进一步进行了展望。以期为白葡萄酒品质的提高提供有效的技术指导。     

白葡萄酒中蛋白质含量的测定—考马斯亮蓝G—250法

蛋白质以及它的化合物是葡萄酒中的重要成份之一，在酒中它和多肽类参与了产品感观特性和物理特性的构成，但白葡萄酒中过多的蛋白质，会引起葡萄酒的混浊和沉淀。因此在研究和解决葡萄酒的蛋白稳定性问题时，蛋白质的定量测定是很重要的方面。而目前多测定粗蛋白含量，即...     

Effect of using bentonite during fermentation on protein stabilisation and sensory properties of white wine

The bentonite use to remove proteins from white wine is a widespread practice that prevents protein haze formation after bottling. However, an excess of bentonite can have negative effects on both the aromatic profile of young white wines and the quality of the foam of sparkling wines. Therefore, the optimisation of bentonite amount to be used and the moment of its application during winemaking to minimise wine quality losses are of great interest for winemakers. This paper analyses how applying an equal bentonite dose at different stages (must clarification; beginning, middle and end of fermentation) on two scales (industrial and pilot) affects the protein content and stability, physical–chemical characteristics, aromatic profile and foam quality of the obtained wines. No important differences in the oenological parameters were observed between industrial and pilot scales, whereas the scale of the experimental treatments affected protein stability, aroma composition and foam quality of the wines.     

The effect of bentonite fining at different stages of white winemaking on protein stability

Background and Aims: Bentonite fining to remove protein is the most widely used treatment to prevent protein haze in white wines. Bentonite can be added at different stages during winemaking. This study aimed to determine the best time to add bentonite. Methods and Results: Unstable juices were vinified after bentonite fining of juice, or with bentonite added either early or late in fermentation. Different addition rates of bentonite were used and bentonite was either added in one or two additions. Fermentation rates were observed and protein stability and bentonite fining rates of the resultant wines were determined. Conclusions: Adding bentonite during fermentation or fining finished wines was the most efficient option in terms of amounts of bentonite required. Fermenting with bentonite present also may increase fermentation rates. Significance of the Study: Using the least bentonite necessary for heat stability is important for winemakers for quality, cost and environmental reasons. This study describes ways in which bentonite addition rates can be minimised.     

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.     

Proteins in white wine, I: Procyanidin occurrence in soluble proteins and insoluble protein hazes and its relationship to protein instability

The presence of procyanidins in wine protein fractions was established by a chemical assay and by pyrolysis DI-EI MS/MS of proteins. The chemical assay, involving acid-catalysed oxidative degradation of the procyanidins, gave cyanidin which was specifically quantified by HPLC. The assay was calibrated with purified grape seed tannin (GST); procyanidin was expressed in μg GST. Cyanidin yields were little altered by the presence of a large excess of protein. The limit of detection of the assay was 1 μg GST and the limit of quantification 3.5 μg GST. Both heat-induced and natural hazes isolated from various white wines were all shown to contain procyanidins, with a content ranging from < 0.02 to 4.9% (w/w). Although a crude soluble protein isolate from white wine contained a detectable amount of procyanidins, none were found in fractions separated chromatographically from this isolate. This observation, and the absence of procyanidins in resolubilised heat-induced haze, demonstrated that procyanidins are only weakly associated with both heat-induced hazes and soluble wine proteins. Nevertheless, procyanidins appear to be implicated in the formation of protein hazes in wine, because many soluble wine proteins that had been rendered free of procyanidins would precipitate to give haze in wine but not in model wine which was devoid of phenolic compounds.