Influence of partial dealcoholization by reverse osmosis on red wine composition and sensory characteristics

Comparison of ancestral and traditional methods for elaborating sparkling wines

This work compares the ancestral method for elaborating sparkling wines with the most widely used traditional method. Ancestral method is a single fermentation procedure in which the fermenting grape must is bottled before the end of alcoholic fermentation whereas traditional method involves a second fermentation of a base wine inside a bottle. Macabeo grapes were used to elaborate a traditional sparkling wine and two ancestral sparkling wines, one with a low yeast population and one with a high yeast population. The findings indicate that ancestral sparkling wines have lower ethanol content and can be elaborated using lower sulphur dioxide levels. In general, ancestral sparkling wines showed similar protein concentration, higher polysaccharide content, similar or better foamability (HM) than the traditional sparkling wine., No differences were found in the foam stability (HS). In addition, the sensory analysis indicated that ancestral sparkling wines have smaller bubble size, lower CO2 aggressivity, they seemed to have longer ageing time and were scored better than the traditional sparkling wine. These results therefore indicate that the ancestral method is of great interest for the elaboration of high-quality sparkling wines.

The Optimisation of Bitter Gourd-Grape Beverage Fermentation Using a Consolidated Response Surface Methodology (RSM) and Artificial Neural Network (ANN) Approach

The present study adopted a response surface methodology (RSM) approach validated by artificial neural network (ANN) models to optimise the production of a bitter gourd-grape beverage. Aset of statistically pre-designed experiments were conducted, and the RSM optimisation model fitted to the obtained data, yielding adequately fit models for the monitored control variables R2 values for alcohol (0.79), pH (0.89), and total soluble solids (TSS) (0.89). Further validation of the RSM model fit using ANN showed relatively high accuracies of 0.98, 0.88, and 0.82 for alcohol, pH, and TSS, respectively, suggesting satisfactory predictability and adequacy of the models. A clear effect of the optimised conditions, namely fermentation time at (72 h), fermentation temperature (32.50 and 45.11 °C), and starter culture concentration (3.00 v/v) on the total titratable acidity (TTA), was observed with an R2 value of (0.40) and RSM model fit using ANN overall accuracy of (0.56). However, higher TTA values were observed for samples fermented for 72 h at starter culture concentrations above 3 mL. The level of 35% bitter gourd juice was optimised in this study and was considered desirable because the goal was to make a low-alcohol beverage.

Carbonic maceration vinification: A tool for wine alcohol reduction

The increase in alcohol content in wine due to climate change is one of the main challenges that winemakers face today. Previous studies have indicated that carbonic maceration processing can be used to obtain a wine fraction with lower alcoholic strength. The aim of this study was to determine the effectiveness of this technique in obtaining wines with lower alcohol content. For this purpose, seven trials were carried out, studying a total of 63 wines. The physico-chemical, phenolic and aromatic composition of the wines was analysed using official methods and gas chromatography. The results showed that it is possible to obtain a fraction of carbonic maceration wine (25-35% of the total) with a reduction in alcohol content of up to almost 4% depending on the vinification conditions and the grape variety used. Therefore, this CM fraction, marketed on its own, could be a low-alcohol alternative to red wines.

Influence of the Processing Parameters on the Aroma Profile and Chemical Composition of Conventional and Ecological Cabernet Sauvignon Red Wines during Concentration by Reverse Osmosis

Wine aroma represents one of the most important quality parameters and it is influenced by various factors, such as climate conditions, viticulture and vinification techniques, storage conditions, etc. Wines produced from conventionally and ecologically grown grapes of the same variety have different chemical compositions and aroma profiles. The composition of wine can also be influenced by the additional treatment of wine, such as the concentration of wine by reverse osmosis (RO). The aim of this study was to investigate the influence of four different pressures (2.5, 3.5, 4.5 and 5.5 MPa) and two temperature regimes (with and without cooling) on the aroma profile and chemical composition of conventional and ecological Cabernet Sauvignon red wine during concentration by reverse osmosis. The results showed that different processing parameters influenced the permeate flux, the retentate temperature and the compounds retention. Higher working pressures (4.5 and 5.5 MPa) and the regime, with cooling, resulted in a higher retention of the total aroma compounds than the opposite processing parameters. The retention of individual compounds depended also on their chemical properties and their interactions with the membrane surface. The reverse osmosis membranes proved to be permeable for ethanol, acetic acid or undesirable 4-ethylphenol and 4-ethylguaiacol that made them applicable for their correction or removal.

Influence of Reverse Osmosis Process in Different Operating Conditions on Phenolic Profile and Antioxidant Activity of Conventional and Ecological Cabernet Sauvignon Red Wine

Red wine polyphenols are responsible for its colour, astringency, and bitterness. They are known as strong antioxidants that protect the human body from the harmful effects of free radicals and prevent various diseases. Wine phenolics are influenced by viticulture methods and vinification techniques, and therefore, conventionally and ecologically produced wines of the same variety do not have the same phenolic profile. Ecological viticulture avoids the use of chemical adjuvants in vineyards in order to minimise their negative influence on the environment, wine, and human health. The phenolic profile and antioxidant activity of wine can also be influenced by additional treatments, such as concentration by reverse osmosis. The aim of this study was to investigate the influence of four different pressures (2.5, 3.5, 4.5, and 5.5 MPa) and two temperature regimes (with and without cooling) on the phenolic profile and antioxidant activity of conventional and ecological Cabernet Sauvignon red wine during concentration by reverse osmosis. The results showed that retention of individual phenolic compounds depended on the applied processing parameters, chemical composition of the initial wine, and chemical properties of a compound. Higher pressure and retentate cooling favoured the retention of total polyphenols, flavonoids, and monomeric anthocyanins, compared to the opposite conditions. The same trend was observed for antioxidant activity.

Comparison between Membrane and Thermal Dealcoholization Methods: Their Impact on the Chemical Parameters, Volatile Composition, and Sensory Characteristics of Wines

Over the last few years, the dealcoholization of wine has piqued the interest of winemakers and researchers. Physical dealcoholization methods are increasingly used in the dealcoholization of wines because they can partially or completely reduce the alcohol content of wines. This study aimed to compare the chemical parameters, volatile composition and sensory quality of white, rosé and red wines dealcoholized by two physical dealcoholization methods: reverse osmosis (RO) and vacuum distillation (VD) at 0.7% v/v ethanol. RO and VD effectively reduced the ethanol concentration in all wines to the required 0.7% v/v, but also significantly affected most chemical parameters. The pH, free sulfur dioxide, total sulfur dioxide, and volatile acidity decreased significantly due to dealcoholization by RO and VD, while reducing sugars and total acidity increased significantly. VD resulted in higher color intensity, which was perceptible in dealcoholized rosé and red wines, while RO caused notable color differences in dealcoholized white and red wine fractions. RO were richer in esters (more ethyl esters and isoamyl acetate), higher alcohols, organic acids, terpenics and C₁₃-norisoprenoids, and carbonyl compounds, while wines dealcoholized with VD had lower levels of these volatile compounds, which may reflect both the loss of esters into the distillate during evaporation and condensation (in the case of VD) and a shift in the chemical equilibrium responsible for ester formation and hydrolysis after ethanol removal. β-damascenone exhibited the highest OAV in all wines, however, losses equal to 35.54–61.98% in RO dealcoholized fractions and 93.62% to 97.39% in VD dealcoholized fractions were observed compared to the control wines. The predominant aroma series in the original and dealcoholized wines were fruity and floral but were greatly affected by VD. Sensory evaluation and PCA showed that dealcoholization by RO improved the fruity and floral notes (in rosé and red wines), color intensity, sweetness, viscosity, and aroma intensity better than dealcoholization by VD, while VD mainly enhanced the color of the dealcoholized wines. Both methods increased the acidity of the respective dealcoholized wines. Nevertheless, RO dealcoholized wines achieved higher acceptance by the panelists than VD dealcoholized wines. Therefore, RO may be a better method for producing dealcoholized (0.7% v/v) wines with minimal impact on aroma and sensory quality.

Techniques for Dealcoholization of Wines: Their Impact on Wine Phenolic Composition, Volatile Composition, and Sensory Characteristics

The attention of some winemakers and researchers over the past years has been drawn towards the partial or total dealcoholization of wines and alcoholic beverages due to trends in wine styles, and the effect of climate change on wine alcohol content. To achieve this, different techniques have been used at the various stages of winemaking, among which the physical dealcoholization techniques, particularly membrane separation (nanofiltration, reverse osmosis, evaporative perstraction, and pervaporation) and thermal distillation (vacuum distillation and spinning cone column), have shown promising results and hence are being used for commercial production. However, the removal of alcohol by these techniques can cause changes in color and losses of desirable volatile aroma compounds, which can subsequently affect the sensory quality and acceptability of the wine by consumers. Aside from the removal of ethanol, other factors such as the ethanol concentration, the kind of alcohol removal technique, the retention properties of the wine non-volatile matrix, and the chemical-physical properties of the aroma compounds can influence changes in the wine sensory quality during dealcoholization. This review highlights and summarizes some of the techniques for wine dealcoholization and their impact on wine quality to help winemakers in choosing the best technique to limit adverse effects in dealcoholized wines and to help meet the needs and acceptance among different targeted consumers such as younger people, pregnant women, drivers, and teetotalers.

Assessing the sensory and physicochemical impact of reverse osmosis membrane technology to dealcoholize two different beer styles

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Reverse osmosis results in significant losses in volatile compounds and modified sensory profiles.

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Volatile losses appear to be related to compound structure, not compound size.

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Reverse osmosis efficiency varies between beer styles, with longer processing times for stouts.

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Reverse osmosis membranes are susceptible to fouling over time, affecting overall product quality.

A pilot scale dealcoholisation unit fitted with reverse osmosis (RO) membranes was used to directly compare two beer matrices (stout, lager, ~ 5% ABV) and their dealcoholized counterparts (~0.5% ABV), for physicochemical properties (volatiles, pH, ABV, polyphenols, bitterness) and sensory profiles using a trained descriptive panel (n = 12). The efficiency and consistency of RO membranes were evaluated by replicate dealcoholisation trials (n = 3) for each beer. Statistical analysis revealed significant reductions (p < 0.05) in key volatile compounds with linear structures (ethyl octanoate, octan-1-ol) compared to those with increased levels of branching (3-methylbutyl acetate, 2-methylpropan-1-ol). Significant reductions (p < 0.0001) in ‘fruity/estery’, ‘alcoholic/solvent’, ‘malty’, ‘sweetness’ and ‘body’ sensory attributes were also discovered. Finally, longer processing times for the stout across replicate trials suggested membrane clogging, whilst differences in volatile reduction suggested membrane fouling. This novel research proposes compound structure, rather than compound size, impacts RO membrane permeability and resulting sensory quality.

Aroma Profile and Chemical Composition of Reverse Osmosis and Nanofiltration Concentrates of Red Wine Cabernet Sauvignon

Wine aroma represents one of the main properties that determines the consumer acceptance of the wine. It is different for each wine variety and depends on a large number of various chemical compounds. The aim of this study was to prepare red wine concentrates with enriched aroma compounds and chemical composition. For that purpose, Cabernet Sauvignon red wine variety was concentrated by reverse osmosis (RO) and nanofiltration (NF) processes under different operating conditions. Different pressures (2.5, 3.5, 4.5 and 5.5 MPa) and temperature regimes (with and without cooling) were applied on Alfa Laval LabUnit M20 equipped with six composite polyamide RO98pHt M20 or NF M20 membranes. Higher pressure increased the retention of sugars, SO₂, total and volatile acids and ethanol, but the temperature increment had opposite effect. Both membranes were permeable for water, ethanol, acetic acid, 4-ethylphenol and 4-ethylguaiacol and their concentration decreased after wine filtration. RO98pHt membranes retained higher concentrations of total aroma compounds than NF membranes, but both processes, reverse osmosis and nanofiltration, resulted in retentates with different aroma profiles comparing to the initial wine. The retention of individual compounds depended on several factors (chemical structure, stability, polarity, applied processing parameters, etc.).

Influence of Processing Parameters on Phenolic Compounds and Color of Cabernet Sauvignon Red Wine Concentrates Obtained by Reverse Osmosis and Nanofiltration

In this study, Cabernet Sauvignon red wine was subjected to reverse osmosis and nanofiltration processes at four different pressures (25, 35, 45, and 55 bar) and two temperature regimes (with and without cooling). The aim was to obtain concentrates with a higher content of phenolic compounds and antioxidant activity and to determine the influence of two membrane types (Alfa Laval RO98pHt M20 for reverse osmosis and NF M20 for nanofiltration) and different operating conditions on phenolics retention. Total polyphenol, flavonoid, monomeric anthocyanin contents, and antioxidant activity were determined spectrophotometrically. Flavan-3-ols and phenolic acids were analyzed on a high-performance liquid chromatography system and sample colour was measured by chromometer. The results showed that the increase in applied pressure and decrease in retentate temperature were favorable for higher phenolics retention. Retention of individual compounds depended on their chemical structure, membrane properties, membrane fouling, and operating conditions. Both types of membranes proved to be suitable for Cabernet Sauvignon red wine concentration. In all retentates, phenolic compounds content was higher than in the initial wine, but no visible color change (ΔE* < 1) was observed. The highest concentrations of phenolic compounds were detected in retentates obtained at 45 and 55 bar, especially with cooling.

Dealcoholization of Korean traditional rice wine, takju, combining thermal, bentonite clarification or reverse osmosis treatment

The objective of this study was to prepare low-alcoholic takju. Low-alcohol (3.06%) and dealcoholized (0.04-0.28%) takju samples were prepared by adopting bentonite clarification, heat and reverse osmosis treatments. The dealcoholization of takju, in most cases, significantly (p < 0.05) reduced the total mineral (from 505.80 to 258.61 mg/L), free amino acid (from 989.81 to 293.58 mg/mL), antioxidant potentials and total phenolic (from 345.30 to 156.30 µg GAE/mL) contents remained in the control to RO-3 (takju sample obtained from 3-time reverse osmosis and heat treatment). Similarly, the content of volatile compounds was also significantly (p < 0.05) decreased with the dealcoholization treatments. The finding of this study clearly showed that dealcoholized takju could be prepared but at the expense of reduced nutritional and antioxidant potentials. This study could be an exemplary in promoting traditional beverages in different countries by producing low or alcohol-free drinks.

Effects of different oenological techniques on the elaboration of adequate base wines for red sparkling wine production: phenolic composition, sensory properties and foam parameters

BACKGROUND

In red sparkling winemaking it is essential to obtain base wines with moderate alcohol content, adequate mouthfeel and color intensity. The aim of this work was to study oenological techniques to obtain adequate base wines for production of red sparkling wine by traditional methods: pre-fermentative cold maceration with dry ice and délestage with premature grapes; and sugar reduction in must and partial dealcoholisation of wine with mature grapes. The effect on oenological parameters, e.g. phenolic content, foam and sensory characteristics, was studied in sparkling wines aged on the lees in bottles for 9 months followed by aging for12 months in bottles after disgorging.

RESULTS

Pre-fermentative cold maceration was the only treatment that increased the content of anthocyanins in sparkling wines at both stages of aging. Sparkling wines elaborated using délestage showed the highest mean values of the degree of polymerization of proanthocyanidins. Sparkling wines from mature grapes were given higher valuation in the gustatory phase. Sparkling wines elaborated using pre-fermentative cold maceration were given the highest valuation for foam quality.

CONCLUSIONS

Pre-fermentative cold maceration is a viable alternative to common techniques for increasing the anthocyanin content in wines from premature grapes. It would therefore be a good option to obtain adequate base wines. © 2019 Society of Chemical Industry.

Volatile profile of reduced alcohol wines fermented with selected non-Saccharomyces yeasts under different aeration conditions

Over the last decades there has been an increase in ethanol concentration in wine. High ethanol concentration may impact negatively wine flavor and can be associated with harmful effects on human health. In this study, we investigated a microbiological approach to reduce wine ethanol concentration, using three non-Saccharomyces yeast strains (Metschnikowia pulcherrima, Torulaspora delbrueckii and Zygosaccharomyces bailii) in sequential fermentations with S. cerevisiae under different aeration conditions. At the same time, we evaluated the volatile profile of the resulting reduced alcohol Chardonnay wines. Results showed that the non-Saccharomyces yeasts tested were able to reduce wine ethanol concentration when oxygen was provided. Compared to S. cerevisiae wines, ethanol reduction was 1.6% v/v, 0.9% v/v and 1.0% v/v for M. pulcherrima, T. delbrueckii and Z. bailii sequential fermentations, respectively. Under the conditions evaluated here, aeration did not affect acetic acid production for any of the non-Saccharomyces strains tested. Although aeration affected wine volatile profiles, this was depended on yeast strain. Thus, wines produced with M. pulcherrima under aeration of 0.05 volume of air per volume of culture per minute (VVM) showed excessive ethyl acetate content, while Z. bailli wines produced with 0.05 VVM aeration had increased concentrations of higher alcohols and volatile acids. Increased concentrations of these compounds over their sensory thresholds, are likely to impact negatively on wine sensory profile. Contrarily, all three non-Saccharomyces strains under 0.025 VVM aeration conditions produced wines with reduced ethanol concentration and acceptable chemical volatile profiles.

Reducción del contenido de alcohol y pH de vinos tintos Pinot noir y Tannat empleando uvas con diferentes niveles de maduración

El objetivo de esta investigación fue determinar la efectividad de la mezcla de mostos de uvas con diferente grado de maduración para la obtención de vinos Pinot noir y Tannat con menor contenido de alcohol y pH. En envero, se extrajo mosto de uvas inmaduras que se conservó a 4 ∘C hasta su uso. En madurez tecnológica, las uvas cosechadas fueron despalilladas, estrujadas y distribuidas en seis recipientes. Tres fueron vinificados de forma tradicional, mientras que en los otros tres se realizó una sustitución de 3 L del mosto de uva madura por 3 L del mosto de uvas inmaduras. Ambos tratamientos realizaron una maceración fermentativa de 7 días. Se determinó la composición básica del vino, color, concentración de fenoles totales, antocianos, catequinas y proantocianidinas a los dos meses del descube. La sustitución de mosto permitió elaborar vinos Pinot noir y Tannat con menor contenido de alcohol y pH, sin reducir las concentraciones de polifenoles totales, catequinas o antocianos. El efecto sobre la concentración de proantocianidinas fue variable de acuerdo con el cultivar y año de vendimia. Los vinos Tannat reducidos en alcohol presentaron mayor intensidad de color, menor tono e igual cromaticidad que los vinos testigos.

Volatile and sensory profiling of Shiraz wine in response to alcohol management: comparison of harvest timing versus technological approaches

The aim of this study was to compare the volatile and sensory profiles of Australian Shiraz red wines produced by several methods to achieve alcohol concentrations of 10.5 and 13.5% v/v. These levels were considerably lower contents than the commercial wine (16-17% v/v) that was produced from this vineyard site. Wines were produced by: (i) harvest timing (19.3, 24 and 29.3 Brix); (ii) blending equal proportions of early harvest (19.3 Brix) and late harvest wines (29.3 Brix); and (iii) dealcoholization using reverse osmosis followed by a membrane contactor. Dealcoholization caused a significant loss of volatile compounds, particularly esters, while the blending treatment had an averaging effect on most analytes. Sensory descriptive analysis of treatments with 10.5% v/v alcohol showed that the perception of the herbaceous attribute was more intense in the early harvest wines in comparison to the dealcoholized wines, while those of dark fruit, raisin/prune, astringency and alcohol were lower. No sensory differences were found amongst the 13.5% v/v wines, except for alcohol. Sensory and compositional data were modelled by means of Common Dimension (ComDim) multi-block analysis and indicated which chemical components are important to the perceived wine sensory properties. Insights from this study will provide knowledge that may be applied to control or moderate both unripe sensory attributes in addition to a deficiency of ripe fruit aromas or mouthfeel characteristics in reduced-alcohol red wines.

Recovery of Anthocyanins Using Membrane Technologies: A Review

Anthocyanins are naturally occurring polyphenolic compounds and give many flowers, fruits and vegetable their orange, red, purple and blue colors. Besides their color attributes, anthocyanins have received much attention in recent years due to the growing evidence of their antioxidant capacity and health benefits on humans. However, these compounds usually occur in low concentrations in mixtures of complex matrices, and therefore large-scale harvesting is needed to obtain sufficient amounts for their practical usage. Effective fractionation or separation technologies are therefore essential for the screening and production of these bioactive compounds. In this context, membrane technologies have become popular due to their operational simplicity, the capacity to achieve good simultaneous separation/pre-concentration and matrix reduction with lower temperature and lower operating cost in comparison to other sample preparation methods. Membrane fractionation is based on the molecular or particle sizes (pressure-driven processes), on their charge (electrically driven processes) or are dependent on both size and charge. Other non-pressure-driven membrane processes (osmotic pressure and vapor pressure-driven) have been developed in recent years and employed as alternatives for the separation or fractionation of bioactive compounds at ambient conditions without product deterioration. These technologies are applied either individually or in combination as an integrated membrane system to meet the different requirements for the separation of bioactive compounds. The first section of this review examines the basic principles of membrane processes, including the different types of membranes, their structure, morphology and geometry. The most frequently used techniques are also discussed. Last, the specific application of these technologies for the separation, purification and concentration of phenolic compounds, with special emphasis on anthocyanins, are also provided.

Selection of non-Saccharomyces yeasts to be used in grape musts with high alcoholic potential: a strategy to obtain wines with reduced ethanol content

Ethanol content of wine has increased over the last decades as consequence of searching phenolic maturity, requiring increased grape maturity. This may result in the production of wines with excessive alcohol levels (sometimes more than 15% (v/v)), sluggish and stuck fermentations and excessive volatile acidity. Many strategies to reduce ethanol in wines are being studied, and microbial methods have some additional advantages. However, because of the broad intra- and interspecies variability, new selection criteria should be included. Therefore, the goal of the present work was to design and evaluate a simple and integral procedure for non-Saccharomyces yeast selection. This strategy allowed selection of yeasts that presented successful implantation in grape must with high alcohol potential and their use in co-cultures could reduce the ethanol in wines. A total of 114 native non-Saccharomyces yeasts were assayed to determine their respiratory, fermentative and physiological characteristics of enological interest. Hanseniaspora uvarum BHu9 and BHu11, H. osmophila BHo51, Starmerella bacillaris BSb55 and Candida membranaefaciens BCm71 were selected as candidates to design co-culture starters.

Changes in volatile composition and sensory attributes of wines during alcohol content reduction

A desirable sensory profile is a major consumer driver for wine acceptability and should be considered during the production of reduced-alcohol wines. Although various viticultural practices and microbiological approaches show promising results, separation technologies such as membrane filtration, in particular reverse osmosis and evaporative perstraction, in addition to vacuum distillation, represent the most common commercial methods used to produce reduced-alcohol wine. However, ethanol removal from wine can result in a significant loss of volatile compounds such as esters (ethyl octanoate, ethyl acetate, isoamyl acetate) that contribute positively to the overall perceived aroma. These losses can potentially reduce the acceptability of the wine to consumers and decrease their willingness to purchase wines that have had their alcohol level reduced. The change in aroma as a result of the ethanol removal processes is influenced by a number of factors: the type of alcohol reduction process; the chemical-physical properties (volatility, hydrophobicity, steric hindrance) of the aroma compounds; the retention properties of the wine non-volatile matrix; and the ethanol level. This review identifies and summarises possible deleterious influences of the dealcoholisation process and describes best practice strategies to maintain the original wine composition. © 2016 Society of Chemical Industry.

Non-conventional Yeast Species for Lowering Ethanol Content of Wines

Rising sugar content in grape must, and the concomitant increase in alcohol levels in wine, are some of the main challenges affecting the winemaking industry nowadays. Among the several alternative solutions currently under study, the use of non-conventional yeasts during fermentation holds good promise for contributing to relieve this problem. Non-Saccharomyces wine yeast species comprise a high number or species, so encompassing a wider physiological diversity than Saccharomyces cerevisiae. Indeed, the current oenological interest of these microorganisms was initially triggered by their potential positive contribution to the sensorial complexity of quality wines, through the production of aroma and other sensory-active compounds. This diversity also involves ethanol yield on sugar, one of the most invariant metabolic traits of S. cerevisiae. This review gathers recent research on non-Saccharomyces yeasts, aiming to produce wines with lower alcohol content than those from pure Saccharomyces starters. Critical aspects discussed include the selection of suitable yeast strains (considering there is a noticeable intra-species diversity for ethanol yield, as shown for other fermentation traits), identification of key environmental parameters influencing ethanol yields (including the use of controlled oxygenation conditions), and managing mixed fermentations, by either the sequential or simultaneous inoculation of S. cerevisiae and non-Saccharomyces starter cultures. The feasibility, at the industrial level, of using non-Saccharomyces yeasts for reducing alcohol levels in wine will require an improved understanding of the metabolism of these alternative yeast species, as well as of the interactions between different yeast starters during the fermentation of grape must.

Partial dealcoholization of red wine by nanofiltration and its effect on anthocyanin and resveratrol levels

The present work studies the use of nanofiltration for the production of red wine concentrate with low alcohol content. Factorial design was applied to measure the influences of transmembrane pressure (10-20 bar) and temperature (20-40 ℃) on the retention of valuable components such as anthocyanins and resveratrol, and on the nanofiltration membrane performance. The highest retention of anthocyanin and resveratrol was achieved at low temperature (20 ℃), while the high transmembrane pressure (20 bar) was found to increase the permeate flux considerably. The experiments demonstrated that nanofiltration appears as a valid technique for the production of low alcohol content red wine concentrate. Reduction of volume by a factor of 4, leads to 2.5-3 times more anthocyanins and resveratrol in the wine concentrates. The final new wine products - obtained by using various forms of reconstitution of the concentrated wine - had low alcohol content (4-6 % by volume) and their sensory attributes were similar to those of the original wine.