Effects of fining with different bentonite labels and doses on colloidal stability and colour of a Valpolicella red wine

This study addressed four different labels of activated sodium bentonite during the fining of a young Valpolicella red wine. Preliminary tests determined the bentonite dose (0.15, 0.30 or 0.50 g L^?1) that would achieve colloidal stability, and this dose was further applied during laboratory‐scale trials. The bentonites were characterised by physico‐chemical parameters, and the effects of the label and dose on the wine colloidal stability, proteins, colour indices and phenolic compounds were measured. The results demonstrated that 0.50 g L^?1 for every bentonite label provided colloidal stabilisation without harshly affecting the colour. Unlike to what happens in white wines the least charged bentonite labels were effective at stabilising the red wine colloidal state by partially reducing its protein content. Simultaneously, the most negatively charged clay samples determined the largest depletions on the total polyphenols, anthocyanins, tannins and polymeric pigments. The differentiated action of clays with different surface charge density among white and red wines may be explained by the interaction mediated by positively charged anthocyanins towards either protein or tannin depletion. Although pioneering, these results may move towards the definition of a safe, allergen‐free, and effective adjuvant for colloidal stabilisation targeted to wine type.     

In-line dosing for bentonite fining of wine or juice: Contact time, clarification, product recovery and sensory effects

Field tests to evaluate in-line dosing with bentonite followed by centrifugation as an alternative to batch fining for protein haze control in white wine or juice were undertaken. The tests were performed at a commercial winery with a Sultana wine and Gordo (Muscat of Alexandria) juice and using two types of bentonite: Vitiben and SIHA-Active-Bentonite G. Fining performance was monitored by heat testing and quantification of heat unstable protein by HPLC. Heat test turbidity and heat unstable protein concentration decreased to stable values between 30 s and 2 min after bentonite injection. Sensory evaluation of Sultana wine fined with Vitiben by balanced reference duo-trio difference tests detected no difference between untreated, in-line dosed, and batch fined wine. Furthermore the volume of wine or juice occluded in lees can be substantially reduced by centrifugal compaction. However, incomplete separation of bentonite from wine or juice during centrifugation produced a carryover of 30% of the added bentonite into the clarified wine. This carryover problem may be mitigated, inter alia, by reducing operating flowrate through the centrifuge or using multiple centrifugation steps (in parallel or series). Therefore, inline dosing followed by centrifugation provides a rapid processing method for protein haze reduction in wine or juice with a decreased volume of lees. It can reduce significant value losses presently arising in the wine industry from batch fining and the resulting quality downgrades that occur in wine recovered from bentonite lees by rotary drum vacuum filtration.     

Evaluation of methods for DNA extraction from must and wine

The quality of wine depends on many factors. One of the most important is the selection of appropriate and defined grape varieties. The analysis of phenolic compounds, amino acids, trace elements and isotopes of wines, used for the identification of grapes varieties, is not sufficient and requires a lengthy analysis period. The development of molecular techniques such as restriction fragment length polymorphism, random amplified polymorphic DNA and microsatellites provides opportunities for the differentiation of grape varieties. In this regard, the use of DNA extracted from must and wine appears to be a good marker for the identification of grape varieties used in wine production. In this study, DNA was extracted from grape, leaf, must and wine samples of Vitis vinifera L. cv. Cabernet Sauvignon, Merlot and Sauvignon Blanc origin and examined using different extraction methods. Of the DNA extraction methods tested, the method using absorption at 260/280 nm (with values of 0.19 and 1.92) was considered the method of choice. Copyright © 2014 The Institute of Brewing & Distilling     

The use of thaumatin and bovine serum albumin as proteins in model wine solutions in bentonite fining

This study examined the viability of using thaumatin and bovine serum albumin (BSA) as proteins in model wine solutions for bentonite fining studies and compared them with unfined New Zealand sauvignon blanc (SB) wine. Bentonite fining trials were performed on model wine solutions and unfined SB wines (pH range 3.5–4.3). Thaumatin was more readily adsorbed onto bentonites of all types than BSA and its adsorption onto bentonite was less affected by the pH of the solution. Specifically, the amount of BSA adsorbed onto bentonite decreased significantly as the pH of the solution approached the isoelectric point (pI) of BSA while thaumatin was adsorbed at that pH due to its higher pI. Changing pH affected protein adsorption of real wine less noticeably than of BSA and thaumatin, and decreasing pH increased protein adsorption in contrast to the model solutions. Neither of the model solutions can fully represent the response of real wine to bentonite fining but they are simple and cost effective to prepare and reacted to changes in bentonite concentration similar to real wine. Thaumatin is potentially a better protein to use in simple model solutions for wine stabilisation studies like filtration where molecular weights are important consideration.     

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.     

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。     

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.     

不同澄清剂在龙眼果酒中的澄清效果及稳定性研究

研究了4种澄清剂对龙眼果酒澄清效果及稳定性的影响。在单因素实验基础上,采用正交实验设计,确立最佳作用条件组合分别为:壳聚糖0.6 g/L,静置15 d,温度20℃;明胶0.2 g/L,静置15 d,温度15℃;蛋清粉0.4 g/L,静置15 d,温度15℃;皂土0.9 g/L,静置15 d,温度25℃。进一步验证对照实验结果表明:4种澄清剂单独使用时均显示了良好的澄清效果,其中以皂土的澄清效果最好,所得澄清酒的透光率高达97.03%,经壳聚糖、皂土澄清处理后的龙眼酒表现出较好的冷热稳定性。      

Ochratoxin A removal from red wine by several oenological fining agents: bentonite,egg albumin,allergen-free adsorbents,chitin and chitosan

The ability of several oenological fining agents to remove ochratoxin A (OTA) from red wine was studied. The adsorbents tested were activated sodium bentonite, egg albumin, allergen-free adsorbents (complex PVPP, plant protein and amorphous silica (complex) and high molecular weight gelatine), and the non-toxic biodegradable polymers (chitin and chitosan). Several dosages within the oenological use range were tested and the wine pH, colour parameters and polyphenol concentration impact associated with each fining agent were studied. Generally, OTA removal achieved in all treatments was higher when the adsorbent dosage increased, but the impact on wine quality also was higher. Chitin at 50?g?hl^?1 removed 18% the OTA without affecting significantly the wine-quality parameters. At the highest dosage tested the gelatine and complex treatments achieved greater OTA removal (up to 39–40%) compared with bentonite, egg albumin and chitin. Moreover, the gelatine and the complex had a lower impact on colour parameters and polyphenol concentration compared with chitosan, whilst OTA was reduced to around 40%. Chitosan achieved the greatest OTA removal (67%), but it strongly affected the wine-quality parameters. Otherwise, bentonite showed a relative efficiency to remove OTA, but the CI value decreased considerably. The egg albumin treatment only removed OTA up to 16% and moreover affected strongly the CI value and CIELab parameters. The results of this survey showed that the non-toxic chitin adsorbent and the allergen-free adsorbents tested could be considered as alternative fining agents to reduce OTA in red wine.     

Fractionation of Sauvignon wine macromolecules by ultrafiltration and diafiltration: impact of protein composition on white wine haze stability

After ultrafiltration (UF) thermally unstable compounds of Sauvignon blanc wines were concentrated in the retentate fractions of 10–30 kDa increasing heat‐induced haze 8.9‐fold, while concentrating haze stabilising species into the retentate fractions of 100–300 kDa with a 5.3‐fold reduction of heat‐induced haze compared to unfiltered wine. Proteins having molecular weights of 18, 23, 33, 35, 40 and 60 kDa were identified as the main haze promoting agents for Sauvignon blanc, where the proteins of 56, 69 and 72 kDa were identified as thermally stable. Potassium sulphate (100 mg L^?1) and magnesium sulphate (25 mg L^?1) did not affect wine haziness at experimental diafiltration (DF) conditions using model wine solutions. Combination of UF and DF is a useful separation method of wine proteins, which is helpful to quantify haziness of individual species and to reveal the interactions between species involving protein haze.     

Influence of sour rotten grapes on the chemical composition and quality of grape must and wine

This study evaluated the effect of grape sour rot on wine fermentation and characterized the chemical composition and the sensory changes in wines produced from rotten musts. Microvinifications were performed during two vintages using healthy Trincadeira and Cabernet Sauvignon red grape varieties to which were added grapes affected by sour rot. Increasing sour rot percentages, up to 50%, contributed to a clear decrease in free run must and final wine yields and induced significant changes in grape must chemical composition expressed by the increase in sugar content, total acidity, volatile acidity, anthocyanins, total phenols, and color intensity. After malolactic fermentation, wines from rotten grapes showed higher values of alcohol content, dry extract, reducing sugar content, total and volatile acidity, anthocyanins, total phenols, and color intensity. Despite the higher levels of reducing sugars, the microbial stability was similar to that of healthy wines. The sensorial evaluation, after malolactic fermentation, showed that both types of wine were not statistically different regarding color, aroma, taste, and overall quality. During 6–8 month storage, wines from rotten grapes showed a significant higher percentage of color loss, suggesting that sour rot is responsible for the decrease in color stability. Nevertheless, the results of sensorial analysis demonstrated that the fermentation of grape musts containing up to 30% sour rot yields wines with similar or even higher-quality scores than wines made with healthy grapes.     

干化对酿酒葡萄品质的影响

贵腐酒、冰酒、稻草酒等通常采用干化葡萄原料进行酿造,适当的干化处理可显著改善或提高酿酒葡萄品质,这是酿造高品质葡萄酒有效的技术途径之一。该文对葡萄干化的常见方式、优缺点进行总结,从葡萄形态和物理特性、表皮和葡萄醪颜色、糖类和有机酸、花色苷和非花色苷多酚以及挥发性成分等方面分别综述干化对酿酒葡萄原料品质的影响,以期为提高干化葡萄酒的质量提供科学依据。     

配制型枸杞酒的澄清方法研究

研究了三种澄清方法对配制型枸杞酒的澄清效果以及这些澄清方法对枸杞酒中生物活性多糖的影响。     

不同澄清剂对葡萄酒澄清效果及葡萄酒品质的影响

本试验从澄清后葡萄酒的澄清效果及下胶处理后酒样的部分理化指标等方面比较研究了明胶和皂土(或明胶和皂土配合使用)、蛋清粉,明胶+蛋清蛋白、植源胶、蛋清蛋白对葡萄酒的澄清效果,确定了不同澄清剂的最佳使用剂量.结果表明,明胶+蛋清蛋白、植源胶在起到澄清作用的同时,葡萄酒综合理化指标及感官质量明显优于其它几种澄清剂法,最佳澄清剂量为明胶+蛋清蛋白90mg/L,植源胶80mg/L.     

Clarifying agents effect on the nitrogen composition in must and wine during fermentation

The effect of static sedimentation with and without clarifying agents (silica sol and gelatine) upon the nitrogenous fraction of musts and wines was studied. Four vinifications were carried out using a Vitis vinifera cv. Cayetana white grape must. Static sedimentation reduced less than other techniques the assimilable nitrogen (FAN), however the employment of fining agents promoted a net decrease. The changes in the amino acids during fermentation were similar in all the experiments carried out. In general, during the first days there was a fast decrease followed by a slight increment and then stabilisation. This decrease fitted, in most of the cases, with first order kinetics. For most of the amino acids, the percent consumption was higher in the must settled with clarifying agents. The clarifying agent’s addition did not have the same effect on the amino acid concentration in the final wines.     

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。     

枣酒和其他果酒澄清净化及陈化技术研究进展

澄清净化处理可以保证果酒的品质并保持最佳感官品评效果和稳定性。陈化技术能够加速果酒的陈酿时间,降低企业生产成本,提高经济效益。该文主要概述了枣酒及其他果酒的澄清净化的方法及陈化技术的研究现状,并对黑化红枣酒的研究现状、澄清净化及人工催陈技术进行总结,以期为枣酒及其他果酒的产业化开发提供一定参考。