Evaluation of the astringency of commercial tannins by means of the SDS–PAGE-based method

The astringency of wines enriched with commercial tannins (CTs) was evaluated by a method based on the SDS–PAGE electrophoresis of salivary proteins after the reaction of saliva with wine. Nineteen CTs tested in synthetic wine at the same pH (3.6) and concentration (1 g/l) gave different values of saliva precipitation index (SPI). The effect of CTs addition was investigated in four wines. Results showed that the wine matrix influenced the astringent capacity of CTs and that became less pronounced as wine polyphenolic complexity increased. For some types of wine, astringency was not affected, indicating that the effect of CTs utilisation is not easily predictable by classical methods. The ability to objectively evaluate the astringency provided by CTs with the SDS–PAGE-based method would supply producers and winemakers with a useful tool to manage the processing conditions and thus to improve the quality of wine.     

Influence of the yeast strain on Monastrell wine colour

Two commercial yeast strains were assayed during the winemaking process of Monastrell grapes to determine their influence on colour and phenolic composition of the resulting wines during alcoholic fermentation and maturation. The results showed that in 2002, the wines did not present great differences but in 2003 higher colour intensity and phenolic compounds content were detected when one of the commercial strains was used. A discriminant statistical analysis clearly showed that different yeasts led to different wines as regard their chromatic characteristics.Industrial relevanceThe importance of yeast in winemaking is extensively known since they are responsible for the transformation of sugars into ethanol and for the formation of the most significant aroma compounds in wines. However, they may also participate in wine colour and this role is usually not taken into account in the wine industry. The choice of a yeast strain is an important factor since these microorganisms have the capacity to retain or adsorb phenolic compounds and, on the other hand, yeast may contribute to stabilizing wine colour, as a result of participating in the formation of vitisins during fermentation or liberating mannoproteins that have the capacity to bind to anthocyanins and tannins, protecting them from precipitation. Two commercial yeast strains were assayed during the winemaking process of Monastrell grapes to determine their influence on colour and phenolic composition of the resulting wines during alcoholic fermentation and maturation. The results showed that higher colour intensity and phenolic compounds content were detected when one of the commercial strains was used, both during fermentation and wine aging, and may be used as a tool during winemaking for obtaining stable and highly coloured wines.     

Alcohol,Tannins, and Mannoprotein and their Interactions Influence the Sensory Properties of Selected Commercial Merlot Wines: A Preliminary Study

The objective of this study was to assess the influence of the interaction among alcohol, tannins, and mannoproteins on the aroma, flavor, taste, and mouthfeel characteristics of selected commercial Merlot wines. Merlot wines (n = 61) were characterized for wine chemistry parameters, including pH, titratable acidity, alcohol, glucose, fructose, tannin profile, total proteins, and mannoprotein content. Agglomerative clustering of these physicochemical characteristics revealed 6 groups of wines. Two wines were selected from each group (n = 12) and profiled by a trained sensory evaluation panel. One wine from each group was evaluated using the electronic tongue (e‐tongue). Sensory evaluation results showed complex effects among tannins, alcohol, and mannoproteins on the perception of most aromas, flavors, tastes, and mouthfeel attributes (P < 0.05). The e‐tongue showed distinct differences among the taste attributes of the 6 groups of wines as indicated by a high discrimination index (DI = 95). Strong correlations (r² > 0.930) were reported between the e‐tongue and sensory perception of sweet, sour, bitter, burning, astringent, and metallic. This study showed that interactions among wine matrix components influence the resulting sensory perceptions. The strong correlation between the e‐tongue and trained panel evaluations indicated the e‐tongue can complement sensory evaluations to improve wine quality assessment.     

Partial dealcoholisation of red wines by membrane contactor technique: influence on colour, phenolic compounds and saliva precipitation index

In this study, red wines from different grape varieties (Merlot, Aglianico and Piedirosso) and containing different alcoholic level (from 13.67 to 15.46% v/v) were treated to diminish the alcoholic percentage of 2, 3 and 5% v/v by a polypropylene hollow fibre membrane contactor apparatus. The wines were analysed before and after partial dealcoholisation. Colour indexes and phenolics were analysed by spectrophotometric methods and HPLC. Wine astringency was evaluated by an astringency index based on the ability of treated wines to precipitate salivary proteins (SPI, Saliva Precipitation Index). For all the levels of dealcoholisation studied, changes in chromatic characteristics, Folin–Ciocalteu index and vanillin reactive flavans were below the methodological errors of the analyses. A loss of malvidin 3-monoglucoside was detected after the dealcoholisation process. Decreasing the ethanol content of wines caused an increase in SPI values.     

Effect of commercial mannoproteins on wine colour and tannins stability

Commercial oenological products containing mannoproteins have the purpose of preventing tartrate salts precipitation or achieving wines with a better mouth-feeling. The evaluation of the influence of three commercial mannoproteins on colour and tannin stability of three different red wines (two from Touriga Nacional and one from Alfrocheiro and Aragonês varieties) was studied. The evolution of colour through time was similar for all modalities, resulting in an increase of polymeric pigments and colour hue and a decrease of other parameters, suggesting that there was no influence of commercial mannoproteins on colour stability. The tannin profile evolution showed a possible stabilizing effect of one of the commercial products for tannins with an mDP between 8 and 14. It is possible that the commercial mannoproteins used in this work have some influence on the tannin aggregation evolution, contributing to the delay of tannin polymerisation in red wines.     

Use of patatin, a protein extracted from potato, as alternative to animal proteins in fining of red wine

The use of plant-derived proteins as wine fining agent has gained increased interest owing to the potential allergenicity of animal proteins in susceptible subjects. Patatin P is the name of a family of glycoproteins that can be recovered from potato aqueous by-product. In this study, a comparative fining trial simulating industrial procedures with 10, 20 and 30?g/hL of commercial preparations of patatin, potassium caseinate, gelatin and egg albumin on an Aglianico (Vitis vinifera L.) red wine was performed. Color indexes and phenolics were analyzed by spectrophotometric methods and HPLC. The potential astringency has been evaluated by an index based on the ability of wine to precipitate salivary proteins (SPI, Saliva Precipitation Index). Patatin is a suitable alternative to animal proteins used as fining agent because: (i) a decrease in total phenolics and tannins after the treatments with 10, 20 and 30 g/hL of commercial preparation containing P was detected; (ii) Patatin, as well as all the fining agents used in this experiment, is able to diminish astringency and the content of red wine phenolics able to react with salivary proteins. Considering all concentrations tested, the effectiveness in reducing proteins reactive towards wine polyphenols was patatin?=?gelatine > egg albumin > casein (p?<?0.05); (iii) at each concentration considered, the treatment with patatin causes no depletion of chromatic characteristics of red wine although a significant slight loss of individual anthocyanins was observed.     

Enological tannins affect acetaldehyde evolution,colour stability and tannin reactivity during forced oxidation of red wine

The addition of enological tannins is a practice admitted and widely used to improve wine phenolic compositions. Although wine ageing is an oxidative process involving phenolic compounds and acetaldehyde production and consumption, the effect of enological tannins on the acetaldehyde and chromatic and phenolic changes of a red wine during oxidation is still not known. In this study, three enological tannins preparations containing gallotannins GT, ellagitannins ET and condensed tannins CT were added to a young commercial Lambrusco red wine in order to obtain wines with three different phenolic compositions. Samples were then treated with hydrogen peroxide to trigger oxidation. All added tannins have determined a production of acetaldehyde greater than control. Acetaldehyde was then consumed in 30 days. The samples treated with CT and ET showed, after oxidation, an increase in colour intensity, determined as the sum of 420, 520 and 620 nm absorbances. A simultaneously increase in polymeric pigments was detected. No significant variation of the Saliva Precipitation Index (SPI), an index useful to give an indirect measure of wine astringency, was observed after 30 days of treatment of CT and ET samples. Results highlight that the addition of CT and ET can help to stabilise colour without affecting wine reactivity towards salivary proteins. A significant role of acetaldehyde has been even detected. These are the first data showing the effect of different enological tannins on the production and consumption of acetaldehyde formation during an oxidation process.     

Influence of the heterogeneity of grape phenolic maturity on wine composition and quality

Nowadays, consumers demand red wines with deep colour, soft tannins and fruit scents, but these wines can only be obtained from grapes with complete phenolic maturity. Diverse methods have been proposed for measuring phenolic maturity. However, all these methods only provide the average value and do not consider any possible heterogeneity. Throughout ripening, grapes were separated according to their density, which revealed the existence of a large heterogeneity. Grapes at harvest were also separated by density in three groups. The higher the density of the grapes the higher ethanol content, pH, colour intensity, total phenolic index and anthocyanin and proanthocyanidin concentrations, and the lower the titratable acidity and bitterness of the wines. When the grapes were denser the wines were also better balanced in flavour and mouthfeel sensation. These results suggest that grape heterogeneity may influence the final wine composition and quality and therefore it should be considered at harvest.     

Use of unripe grapes harvested during cluster thinning as a method for reducing alcohol content and pH of wine

Background and Aims: Deep red full‐bodied wines can only be obtained from grapes with complete phenolic maturity, which frequently produce wines with high pH and alcohol content. The present study focuses on a new procedure for simultaneously reducing pH and ethanol content. Methods and Results: Grapes from cluster thinning were used to produce a very acidic low‐alcohol wine. The wine was treated with high doses of charcoal and bentonite. This odourless and colourless wine was used to reduce pH and ethanol content of wine produced from grapes, which had reached complete phenolic maturity. The anthocyanin and proanthocyanidin concentrations, the mean degree of polymerisation and the monomeric composition of proanthocyanidin of reduced‐alcohol wines were similar to those of their corresponding controls. Since the pH was lower, the colour of the reduced‐alcohol wines was more intense. No significant differences were found between reduced‐alcohol wines and their controls by triangle sensory tests using dark glasses for two of the three studied cultivars. Conclusion: The procedure described allowed production of wines with reduced alcohol content and pH, while retaining similar phenolic content and sensory properties. Significance of the Study: The proposed procedure is easy to apply, does not require specific equipment and offers a means of addressing the problem of wines developing high ethanol and low pH as a result of over‐ripening of grapes.     

Effect of refermentation conditions and micro-oxygenation on the reduction of volatile acidity by commercial S. cerevisiae strains and their impact on the aromatic profile of wines

Herein, we evaluate the applicability of previously characterized commercial and indigenous Saccharomyces cerevisiae strains and non-S. cerevisiae species for the deacidification of white and red wines at a pilot scale. The effect of the refermentation process (mixture of acidic wine with musts from freshly crushed grapes or with residual marc) as well as micro-oxygenation (MO) on acetic acid removal efficiency and wine aromatic composition was also assessed in a red wine. The commercial strains S26 and S29 efficiently reduced both acetic acid (43 and 47%, respectively) and sugar (100%) after 264 h of refermentation of an acidic white wine that was supplemented with grape must. Similar results (60-66% of acetic acid removal) were observed for red wine deacidification using grape must, independently of MO. When residual marc was used for deacidification, strain S26 removed 40% of acetic acid, whereas strain S29 did not initiate refermentation with or without MO. Wines obtained by refermentation with the must had significantly lower acetic acid and a higher total SO₂ concentration in comparison to the wines deacidified by the grape marcs. The volatile aroma compound's composition of deacidified red wines was dependent on the refermentation process used, rather than on MO. The marc-deacidified wine obtained by the use of strain S26 and without MO achieved the best sensory classification. When data from all analytical and sensory evaluation were combined, Principal Component Analysis (PCA) separated the wines into three distinct groups according to the strain and the refermentation process independently of MO. We successfully established an efficient and cheap enological solution for the rectification of volatile acidity of wines.     

Interactions of phenolic and volatile compounds with yeast lees,commercial yeast derivatives and non toasted chips in model solutions and young red wines

Ageing of wines on lees, the use of commercial yeast derivative products and the addition of oak chips to wine permit the release of different compounds such as mannoproteins and polysaccharides into wines during yeast autolysis. These compounds released can interact with phenolic compounds and/or aromatic compounds, also modifying wine sensory perception. For that reason, the aim of this work was to evaluate the interaction of phenolic and volatile compounds of wines with yeast lees, non-toasted oak wood chips and different commercial yeast derivative preparations in model wine solutions and in a real red wine. The results found in this study have shown that most of the phenolic and volatile compounds studied are adsorbed by wood and bound by lees in model wine solutions. However, in the model wines in general, the commercial yeast derivative products studied only interacted with the volatile compounds but not with the phenolic compounds. The adsorption of the phenolic compounds occurred in the first 15 days of treatment, remaining constant for 2 months; however, in the case of volatile compounds, these compounds initially displayed a retention effect, but after 30–60 days, the release of the previously bound compounds was instigated. The adsorption effect on the phenolic and volatile compounds in the model wine solution was not always the same as in the red wine studied, which highlights the important presence of other wine compounds in these interactions.     

Antioxidant Properties of Sparkling Wines Produced with β-Glucanases and Commercial Yeast Preparations

The aim of this study was to evaluate the in vitro antioxidant potential of sparkling wines produced with β-glucanases, autolysated yeasts, yeast cell walls, and purified mannoproteins. Total antioxidant capacity (measured by 2,2-diphenyl-1-picrylhydrazyl [DPPH] radical-scavenging method and ferric reducing antioxidant power [FRAP] assay), and hydroxyl radical-scavenging activity (HRSA) were higher in the wine samples with coadjuvants (in relation to the control wine). The highest values of antioxidant activity were achieved with purified mannoproteins and, in lesser extent, with β-glucanases. Neutral polysaccharides and total proteins were highly and positively correlated with DPPH, FRAP, and HRSA assays. However, correlations between the levels of each different phenolic family and antioxidant and radical-scavenging activities were not found. β-Glucanase and commercial yeast preparations can be excellent coadjuvants to increase the antioxidant properties of sparkling wines. Practical Application: β-Glucanase and commercial yeast preparations can be excellent coadjuvants to increase the antioxidant properties of sparkling wines. The suggested improvement has significant implication for the production of high added value sparkling wines.     

酒度、总酸、pH值以及饮用温度对干红葡萄酒涩味的影响

利用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulphate polyacrylamide gel electrophoresis,SDS-PAGE）分析唾液蛋白与模拟酒反应后蛋白减少比例,并将其表示为涩味强度;同时,以酒度、总酸、pH值以及饮用温度为考察因素,利用二次正交旋转组合设计分析各因子对涩味强度的影响。结果表明：pH值对涩度影响最大,其次是酸度和温度,酒度影响最小;其中pH值和酸度互作效应对涩味的影响显著。     

Influence of some technological practices on the quantity of resveratrol in wine

A study of the effects of some prefermentative and fining practices on the resveratrol concentration in wine was carried out. The trans- and cis-resveratrol contents in a red wine obtained using must hyperoxidation were reduced to about 50% compared with those of control wines; this decrease was greater than that observed for total phenols and catechins. In contrast, sparging the red grapes with SO₂ and ascorbic acid before crushing them resulted in the trans-resveratrol concentration being greater than that of the control wines. Moreover the amounts of trans- and cis-resveratrol in commercial and synthetic wines were determined before and after addition of charcol, polyvinylpolypyrrolidone (PVPP), bentonite, casein, gelatine, and two inert materials, cellulose and diatomaceous earth (kieselgur), used as a filter aid. The results showed that PVPP, charcoal and casein were more effective at removing trans- and cis-resveratrol both in synthetic wine and in commercial wines. In all the wines tested the other fining agents gave a limited decrease (2?–?5%) of trans- and cis-resveratrol. After charcoal and PVPP treatments, significant correlations were observed between the percentage of residual resveratrol and the total phenols in the wines.     

The hybrid grape chambourcin has a role in quality red V. vinifera blends in a New World grape growing region

Chambourcin is a hybrid red wine grape that can consistently produce high-quality wine in many humid climate New World sites including New Jersey and much of the mid-Atlantic region of the United States. Many of these regions can also produce high-quality V. vinifera-based red wine blends. This study examined the influence of chambourcin on the quality of red wine blends of V. vinifera varieties in blinded tasting sessions involving three groups: consumers, wine professionals (non-winemaking), and commercial wine makers. Consumers preferred or rated equally the chambourcin containing blend to the non-chambourcin containing blend. Among wine professionals and commercial wine makers, there was no preference among blends. Even experienced wine makers could not identify wines containing chambourcin and did not rate wines lower if they thought the wines contained chambourcin. This study suggests chambourcin does not detract and rather may enhance high-quality red wine blends and further suggests that wine blend categorization may be better based on hedonic character and not grape genetic heritage. Inclusion of high-quality hybrid grapes, like chambourcin, in red blends of V. vinifera may enhance sustainability of viticulture in New World grape growing regions without sacrifice in the quality of wine that can be produced.     

Fate of three insect growth regulators (IGR) insecticides (flufenoxuron, lufenuron and tebufenozide) in grapes following field application and through the wine-making process

The dissipation of three insecticide flufenoxuron, lufenuron and tebufenozide residues in grapes after field treatments and during the wine-making process was assessed. Residues were determined in grape, must, centrifuged must and wine samples by HPLC-UV after cyclohexane extraction and clean-up on silica-phase cartridges. Vines in vineyards with white and red grapes located in Central Greece were sprayed once with commercial formulations of each insecticide at the recommended doses in experiments carried out in 2004 and repeated in 2006. The insecticide residues in grapes showed slow reduction for a period of 42 days after application following first-order kinetics with dissipation rates ranged from 0.011 to 0.018 mg kg?1 day?1. However, at the recommended pre-harvest interval (PHI) residues did not exceed 0.27 ± 0.03 mg kg?1 for flufenoxuron and lufenuron and 0.68 ± 0.07 mg kg?1 for tebufenozide, and they were clearly lower than the maximum residue limits (MRLs) set by the European Union for grape (2 mg kg?1 for flufenoxuron, 1 mg kg?1 for lufenuron and 3 mg kg?1 for tebufenozide). Grape processing into wine caused an almost complete reduction for flufenoxuron and lufenuron as their residues in wine were below the method LOQs (<0.01 mg l?1), but only a moderate reduction for tebufenozide with concentrations from 0.13 to 0.26 mg l?1 measured in the produced wines. Mean transfer factors for tebufenozide of 0.45 for white 'Roditis' and 0.34 for red 'Cabernet Sauvignon' were found from grapes into wine for the wines processed without maceration. The wine-making technique (with or without maceration) had the same influence on tebufenozide residues in wine. Of the various clarifying agents studied, charcoal was found to be the only one effective in removing tebufenozide residues from wine.     

Prebiotic effects of yacon (Smallanthus sonchifolius Poepp. & Endl), a source of fructooligosaccharides and phenolic compounds with antioxidant activity

Montepulciano is one of the most famous and important red-berried grapes of Italy. This article presents and discusses a comparative study of aroma profile and phenolic content of the Montepulciano wine from the Marches and the Abruzzo regions. The volatile composition of wines was determined by using headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). The PDMS fibre was chosen. The dominating esters in Montepulciano wines were ethyl hexanoate, ethyl decanoate, and ethyl octanoate, whereas phenyl ethanol and 3-methyl-1-butanol were dominating alcohols.Phenolic compounds, namely gallic acid, p-coumaric acid, trans-ferulic acid, caffeic acid, trans-resveratrol, (+)-catechin and (−)-epicatechin, were examined using HPLC-MS with direct injection of wine samples. The total phenolic content of the analysed wines was in the range of 30.4-61.9 mg l⁻¹. The presence of high amounts of esters seems to characterise the volatiles of Montepulciano wines from the Marches, whereas a high level of alcohols was found in Montepulciano wines from Abruzzo. Moreover, multivariate chemometric techniques, such as cluster analysis and principal component analysis, supported this thesis. Headspace solid phase microextraction and gas chromatography-mass spectrometry were used to analyse 20 commercial wine samples (Montepulciano monovarietal red wines) from the Marches (10 samples) and Abruzzo (10 samples).