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.     

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.     

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.     

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.     

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.     

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.     

Effects of noble rot on must composition and aroma profile of Amarone wine produced by the traditional grape withering protocol

The effects of noble rot on the overall quality of Amarone wine, a “Passito” dry red wine, produced by a traditional withering grape process are poorly understood. Wines obtained from healthy and selected grapes infected by noble rot were compared. Validation of the experimental plan was carried out by determining glycerol and gluconic acid content, laccase activity and microbial analysis of the musts. Botrytis cinerea infection produced significant variation in esterase and β-glucosidase activity of grape must. Aroma analysis in healthy and botrytised wines was carried out by SPE extraction followed by GC–MS quantification. A decrease of several fermentative esters was observed in botrytised wine, while wine produced from healthy grapes showed a higher fatty acid content. Molecules such as 1-octen-3-ol, phenylacetaldehyde and furaneol were positively linked to the noble-rotten grapes. Interestingly, γ-nonalactone and 4-carbethoxy-γ-butyrolactone increased, while sherry lactones decreased in botrytised wine. The strong increase of N-(3-methylbutyl)acetamide was related to B. cinerea grape infection.     

Impact of wine manufacturing practice on the occurrence of fining agents with allergenic potential

Proteinogenic wine fining agents are hidden allergens and could present a risk for consumers with allergies. Therefore, the European Parliament adopted Directive 2003/89/EC amending Directive 2000/13/EC to declare ingredients, contaminations and processing aids that are known to trigger allergic reactions. The Amendment Regulation (EU) 1266/2010 excluded the labelling of wines which are processed with hen’s egg and products thereof until 30 June 2012 to get more scientific findings. After 1 July 2012 wine fining agents have to be declared if above 0.25 mg l^–1 (Regulation (EU) 579/2012 in conjunction with article 120 g of Regulation (EU) 1234/2007). The Organisation International de la Vigne et du Vin (OIV) advises this limit of detection (LOD) for potential allergenic residues of proteins. Wine fining agents are processing aids and according to the wine producer’s knowledge will be removed after coagulation by filtration or other production steps. Due to lack of scientific data, residues of fining agents in the final product could not be excluded. In this risk assessment, highly sensitive ELISA methods for ovalbumin of known origin for wine have been developed. The objective was to investigate the presence of allergen residues in wine after certain technological treatments were applied to remove the wine fining agents. For all developed ELISA methods the LODs are in the low µg l^–1 range between 5 and 10 µg l^–1 fining agent, whereas the LOQ varies between 5 and 80 µg l^–1 fining agent. The results of the investigation of well-known wines and fining agents demonstrate that white wines fined with white or ovalbumin from hen’s egg could retain allergens. The use of certain technological procedures during wine processing leads to different results. In white wine, bentonite or sheet filtration followed by sterile filtration lead to wines containing no detectable amounts of ovalbumin. In red wine, especially the final sterile filtration removes the fining agents.     

Influence of decantation of viura must on the cation content. Evolution during wine fermentation and stabilization

Must has many metallic cations which greatly affect wine fermentation, stability and quality. In this study we investigated the influence of clarification of viura must by static sedimentation studying the concentration of four macroelements (potassium, calcium, magnesium and sodium) and of four oligoelements (iron, copper, zinc and manganese). This treatment eliminated potassium (11%), calcium (25%), and a greater proportion of iron (46%). The evolution of cations during fermentation was similar in the clarified sample and in the control. Both young and stablised wines had similar concentrations of these elements.     

澄清剂和酶对梅鹿辄葡萄酒澄清和脱色的影响

用明胶、蛋清、甘草、硅藻土、果胶酶、木瓜蛋白酶等对梅鹿辄红葡萄酒进行澄清。结果表明，这几种澄清剂和酶对葡萄酒都有一定程度的澄清和脱色作用，且随着澄清效果的提高，脱色渐趋严重。兼顾澄清和脱色两方面的因素得出，明胶和木瓜蛋白酶澄清效果好，脱色轻，两者的最佳用量分别为400～500mg／L和50～100mg／L。     

Repercussion of the clarification treatment agents before the alcoholic fermentation on volatile composition of white wines

Albariño must was clarified with two fining agents, as bentonite and silica gel. Alcoholic fermentation was carried out at semi-industrial scale, and the concentration of free monoterpenes, norisoprenoids, C₆-alcohols, higher alcohols, fatty acids, ethyl esters, and acetates was then investigated. The use of bentonite allows loss of several volatile compounds compared to wine control. In a second step, the effect of clarification–stabilization treatments with silica gel on aromatic substances was compared in order to study this influence in white wines elaborated from different aromatic varieties (Albariño and Loureira). The results showed that the use of these fining agent plays a significant role in the wine volatile composition.     

沙棘发酵酒的澄清与稳定工艺研究

为保证沙棘发酵酒货架期的澄清与稳定,采用壳聚糖50g/100L与硅藻土100g/100L组合时,经2~3h澄清后,效果最佳;冷冻处理的最佳温度为-4℃,时间为5d;热处理的温度为34℃、时间为7d时表现最佳,其能量消耗小,成本较低,对果香与酒体的新鲜感影响较小。732钠型树脂可除去钾等离子引起的混浊与沉淀,表现处理时间短,但不能解决金属性混浊。单一处理难以达到理想的澄清稳定效果,需配以其它措施。     

Characterization of the yeast ecosystem in grape must and wine using real-time PCR

The complex microbial ecosystem of grape must and wine harbours a wide diversity of yeast species. Specific oligonucleotide primers for real-time quantitative PCR(QPCR) were designed to analyse several important non-Saccharomyces yeasts (Issatchenkia orientalis, Metschnikowia pulcherrima, Torulaspora delbrueckii, Candida zemplinina and Hanseniaspora spp.) and Saccharomyces spp. in fresh wine must, during fermentation and in the finished wine. The specificity of all primer couples for their target yeast species were validated and the QPCR methods developed were compared with a classic approach of colony identification by RFLP-ITS-PCR on cultured samples. Once the methods had been developed and validated, they were used to study these non-Saccharomyces yeasts in wine samples and to monitor their dynamics throughout the fermentation process. This study confirms the usefulness and the relevance of QPCR for studying non-Saccharomyces yeasts in the complex yeast ecosystem of grape must and wine.     

Influence of the use of bentonite as a riddling agent on foam quality and protein fraction of sparkling wines (Cava)

This paper studies how the use of bentonite to facilitate the riddling process affects the foam properties and the protein fraction of sparkling wines (Cava). In all monovarietal sparkling wines (Macabeu, Xarel.lo, Parellada, Chardonnay and Pinot Noir), the addition of bentonite produced a statistically significant diminution of the Mosalux parameters (HM and HS). This depreciation of the foam quality may be attributed to the direct interaction of bentonite with wine proteins. Concretely the use of bentonite caused a diminution of more of 80% of total the soluble protein. Gel filtration by FPLC showed that bentonite particularly affected the 60 kDa and 20–30 kDa protein fraction. The high molecular fraction, on the other hand, was not affected.     

Residues of the fungicide famoxadone in grapes and its fate during wine production

Famoxadone is a recently applied fungicide to vines that belongs to the oxazolidinedione family. The fate of famoxadone was studied by considering the decay ratio of this fungicide during the maturation of grapes and wine production. The main factors affecting the presence of fungicide residues such as fruit growth, photodegradation, evaporation, thermodegradation and co-distillation were studied with model systems. An experimental field was treated with a commercial product containing famoxadone at the recommended dose. After this application, residues of famoxadone were found in grapes at 0.27 ± 0.06 mg kg^-1. In this field experiment, the half-life (t_1/2;) of famoxadone, which is described by pseudo-first-order kinetics (R² = 0.74), was 18 ± 6 days, resulting from the photodegradation. The famoxadone residue levels in grapes were below the established maximum residues level for Europe (2 mg kg^-1), whilst levels in wine, carried out with and without maceration, were below the calculated limit of detection of the method.     

Assessment of grey mould (Botrytis cinerea) impact on phenolic and sensory quality of Bordeaux grapes,musts and wines for two consecutive vintages

Background and Aims: The impact of grey mould (Botrytis cinerea (B. cinerea)) was quantified on chemical, phenolic and sensory qualities of grapes, derived musts and wines. Methods and Results: Analyses were carried out by using naturally or artificially infected grape berries at ripeness or overripeness. In grape seeds, chemical analyses revealed no major differences between healthy and rotten grapes. In grape skins of Botrytis‐affected berries, concentrations of all the phenolic compounds (anthocyanins and proanthocyanidin monomers, dimers and trimer) decreased drastically. Mean degree of polymerization of the proanthocyanidin polymeric fraction was also affected in skins. Chemical analyses of musts and wines made with different percentages of rotten berries showed a moderate impact of the pathogen on their phenolic composition. Nevertheless, sensory analyses underlined a loss of wine sensory quality perceptible from a threshold as low as 5% of Botrytis‐affected grapes onwards. Conclusion: Phenolic variations and the associated negative impact in grapes, derived musts and wines may be related to oxidation phenomena from B. cinerea. The main effects of severity/age of grey mould and the level of berry maturity are also discussed. Significance of the Study: B. cinerea drastically affects the phenolic and organoleptic properties of grape skins and derived wines. Therefore, prophylactic actions early in the vineyard, evaluation of the sanitary status of the harvested grapes and berry sorting are primordial even under low disease pressure.     

Effect of Esca disease on the phenolic and sensory attributes of Cabernet Sauvignon grapes,musts and wines

Background and Aims: The impact of Esca, a cryptogamic disease affecting woody tissues of grapevines (trunk, branches and shoots), was investigated on phenolic and sensory qualities of Cabernet Sauvignon grapes, derived musts and wines. Methods and Results: Global phenolic analyses revealed no major difference between healthy and affected grapes whereas high‐performance liquid chromatography analyses showed decreases in the skin concentrations of catechin and epicatechin and of anthocyanins for the two vintages assessed. Proanthocyanidin characteristics, and particularly mean degree of polymerisation, were strongly decreased in skin proanthocyanidin polymeric fractions. Chemical analyses of wines made with different percentages of fruit from Esca infected grapevines confirmed the moderate impact of Esca on phenolic composition. Nevertheless, sensory analyses revealed a loss of wine sensory quality perceptible with as little as 5% of affected fruit in wines. Conclusions: Phenolic variations in grapes and in derived wines may be related to changes to grapevine physiology caused by Esca fungi that impact on flavonoid metabolism. The chemical and sensory variations between wines can also be related to the delayed ripening delay of fruit from Esca infected grapevines. Significance of the Study: Esca moderately affected the phenolic composition of grapes and decreased the sensory quality of wines, suggesting a dramatic increase in the economic importance of Esca if no control methods are found.