Total Polyphenol Index Research Articles

Phenolic and colour characteristics of must and wine obtained from red grapes treated by pulsed electric fields. Efficacy of PEF to reduce maceration time in elaboration of red wines

Pulsed electric fields effect was studied on the physico-chemical and general phenolic composition as colour characteristics and stilbene content in must and wine. For this purpose, a continuous pulsed electric fields equipment was used to treat three red grape varieties of DOCa Rioja. Graciano, Tempranillo and Grenache wines from these grapes were elaborated with different maceration times, 2 days in the untreated sample (control) and the PEF-treated sample (PEF), and normal maceration time in another untreated sample (control-NM). Parameters as colour intensity, anthocyanin content, total polyphenol index and tannin content showed no differences between the PEF sample with 2 days of maceration and the control-NM sample, except in the case of Tempranillo wines. Total stilbenes, trans-resveratrol and trans-piceid of Graciano wines elaborated from PEF samples showed a higher concentration than the control wines. Alternatively, PEF wines and control-NM wines showed no differences between them. Tempranillo variety wines presented no differences between the three types of samples. In the Grenache variety, only trans-piceid levels showed differences between control and PEF wines. Moreover, relationship between must and wine characteristics was evaluated and compared between different samples. The trend lines obtained for the CI, TPI and AC parameters for samples of Graciano, Tempranillo and Garnacha indicate that the initial content of compounds extracted significantly affected the days of maceration necessary to obtain the appropriate wine. The results obtained increase the knowledge of pulsed electric fields as a technology available for use in the winery to elaborate red wines with reduced maceration time.

Soil and climate effects on winter wine produced under the tropical environmental conditions of southeastern Brazil

Southeastern Brazil is an emergent region in terms of the production of high-quality fine wines. To contribute to typicity assessment, the soils (morphology, mineralogy, chemical and physical analyses), parent material (geologic maps and portable X-ray fluorescence spectrometry) and climate (temperature and precipitation) were characterized in seven vineyards located in the state of Minas Gerais and São Paulo, Brazil, by carrying out state-of-the-art terroir analysis and assessing the environmental variations of the study sites. A soil profile was described and sampled in the central part of each vineyard. Principal Component Analysis (PCA) biplots were used to analyze the relationships between these factors and the composition of wines (2016, 2017 and 2018 harvests) produced from Syrah in commercial vineyards in different municipalities of Três Corações (TC), Cordislândia (COR), Andradas (AND), São Sebastião do Paraíso (SSP), Três Pontas (TP), Espírito Santo do Pinhal (PIN) and Itobí (ITO). The vineyards were grouped according to soil and climate characteristics. Group A was composed of COR, AND and PIN vineyards, which exhibited the highest correlation with soil Al3+ content and accumulated rainfall. The group’s wines had the lowest ash alkalinity, total polyphenol index (TPI) and pH values and the highest fixed acidity. Group B consisted of the TP and TC vineyards, which had the highest soil organic matter and boron contents and the highest thermal amplitude with similar values (15.4 °C in TC and 15.2 °C in TP); their wines showed average composition. Group C comprised ITO alone, which was characterized by the shallowest and least developed soils. Its wine had the highest flavonol content and high dry extract, color intensity, TPI, alcohol content and sugar values. Group D contained the SSP vineyard, in which the soil subsurface horizons were correlated with the highest wine pH. Late harvest in this vineyard caused the most dehydration of grapes and consequent concentration of most wine compounds (human effect on terroir). The terroir information produced in this study adds substantial value to the wines produced under the tropical environmental conditions of southeastern Brazil, for which such studies are very rare. By characterizing the natural factors (soil, soil parent material and climate) and human factors (vineyard management and wine characteristics) related to terroir, this study can also provide historical information about the wine from this emergent region (the historical factors). In addition, its results can be used to guide producers in their choice of vineyard cultivation sites according to preference in wine composition.

Chemical characterization, antioxidant activity and morphological traits in the leaves of guayule (Parthenium argentatum A. Gray) and its hybrids

In the rubber extraction process, guayule leaves represent an important biomass waste by-product, up to 32%, whose exploitation might contribute to the valorization of the whole plant. The extraction of any of its bioactive compounds or its use as an antioxidant seems to be the most feasible alternative. This study relates guayule leaves morphology to the individual content of 35 compounds (of the 50 tentatively identified), the determination of overall phenolic content and antioxidant activity. The morphological traits allowed the classification of the accessions (27) into three main groups according to size and shape of the leaf, being related to their hybridization. The environment and growing conditions modified the leaf phenotype for USDA germplasm with respect to recent USA studies. The heterogeneity found by different authors in the determination of phenolic content in guayule leaves requires a standardization procedure. Of the two analysis protocols, Total Polyphenol Index (TPI) and Folin–Ciocalteau reagent (Folin) after extracting the leaves at 1 and 24 h, the TPI at 1 h was selected since it was faster and simpler than others and correlated better with the antioxidant activity determined by 2,2-diphenyl-picrylhydrazyl (DPPH). The compounds found in greater quantities corresponded to the chlorogenic acid family, but with no influence with leaf morphology. On the other hand, compounds with smaller concentrations such as gallic acid, an isomer of ferulic acid or the quercetagetin methyl ether glucuronide correlate with aspects of leaf morphology.

Ground vegetation covers increase grape yield and must quality in Mediterranean organic vineyards despite variable effects on vine water deficit and nitrogen status

In the context of a warming climate and widespread soil degradation, successful soil management practices in Mediterranean vineyards should combine environmental (e.g., soil health) and productive (yield and must quality) objectives. With this objective, we tested five soil management practices in two organic farms in Chianti Classico (Italy) across three years. Five treatments were compared: conventional tillage (CT), spontaneous vegetation (S), soil-incorporated cover crop of pigeon bean (Vicia faba L. var. minor (Peterm. em. Harz) Beck. L.) (PBI), a cover crop mixture of barley (Hordeum vulgare L.) and clover (Trifolium squarrosum L.), either mulched (BCM) or incorporated in soil (BCI). We explored the effects of soil management practices on vine stress (SPAD and stem water potential), grape production (yield per plant; number of clusters per plant; cluster weight; berries weight) and must quality (titratable acidity; malic acid; pH; sugar concentration; yeast assimilable N; potential anthocyanins and total polyphenol index). Soil variability was taken into account in the statistical analysis, by testing two sets of soil covariates. A first dataset included the “raw” electrical conductivity and gamma ray total counts. The second dataset consisted in a set of soil covariates obtained by combining data collected by the proximal sensors with the results of the chemical analyses. We found that soil management affected SPAD and stem water potential with variable effects between farms and years. Mulched cover crops showed lower vine SPAD values than tilled treatments at both farms, especially in 2019 and 2020, while spontaneous vegetation effects varied considerably across farms and were comparable to tillage. Conventional tillage also decreased vine water stress compared with S, especially at the colder site in 2020. Mulched cover crops and tillage treatments had similar vine stem water potential at the warmer site. Significantly higher grape yields were found under PBI and S (about +30% compared with the other treatments), mainly due to higher cluster weight. The most productive treatments (PBI and S) also showed higher pH and malic acid concentration but lower anthocyanins and total polyphenol index as compared with the other treatments. Conventional tillage increased yeast assimilable N in 2019 while S showed the lowest values, probably due to a drop in the abundance of N-fixing plant species. On a methodological side we found that including soil parameters as covariates, instead of ECa readings and gamma ray total counts, improved regression models for all the dependent variables studied except for juice pH. Overall, our results indicate that groundcovers induced only a moderate and temporary stress that affected grape production and quality differently. While the barley-clover mixture significantly reduced grape production irrespectively of termination type, S and PBI were associated with higher grape yields. Overall, this study demonstrated that groundcovers can be profitably introduced in vineyards also in Mediterranean climates with positive effects on yields and quality.

Classification of vine-shoots for use as enological additives.

Toasted vine shoots have recently been proposed as enological additives with the aim of improving the sensorial profile of wines. However, so far, there is no simple method for classifying vine shoots for this innovative enological practice. In this study, therefore, an enological aptitude classification for toasted vine shoots has been proposed for the first time. Moreover, given the need for quick techniques to be used in wineries to determine the main phenolic compounds of vine shoots, near-infrared (NIR) spectroscopy has been calibrated and validated. By means of a detailed statistical analysis, an enological classification of toasted vine shoots has been proposed based on their total polyphenol index and (+)-catechin, (-)-epicatechin, ellagic acid, and trans-resveratrol. Moreover, the NIR methodology that was developed showed good validation statistics and acceptable accuracy. This work proposes the first enological toasted vine-shoot classification and it provides a tool for rapid screening, mainly of phenolic compounds, in toasted vine shoots. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Wine composition of Merlot and Cabernet Sauvignon vine clones under the environmental conditions of Serra Gaúcha, Brazil

This study aimed to evaluate the wine composition from vine clones of Merlot (181, 346, 347, 348) and Cabernet Sauvignon (R5, 18A, 163, 338, 341). The grapes were harvested between 2010 and 2012, then on the same day, taken to the winery facility for winemaking. After crushing and destemming the grapes, the musts were transferred to glass containers, where the alcoholic and later malolactic fermentations occurred. Next, the wines were bottled and analyzed, where the classical variables were determined by physicochemical methods, volatile compounds by gas chromatography, and minerals by atomic absorption spectrophotometry. Data were submitted to ANOVA, Tukey test, correlation analysis, and Principal Component Analysis. The clone effect was significant for some variables; however, year and varietal group exerted greater effects. The Merlot group generally had higher values of ethanol, absorbance at 520 nm, color intensity, total polyphenols index, and methanol. On the other hand, the Cabernet Sauvignon group presented higher pH, ashes, alkalinity of ashes, hue, and potassium. Therefore, the three-year average data demonstrate that the evaluated Merlot and Cabernet Sauvignon clones are suitable to produce quality wines in the region, especially Merlot 181, 346, and 348 and Cabernet Sauvignon 18A and 163.

Torulaspora delbrueckii promotes malolactic fermentation in high polyphenolic red wines

Using Torulaspora delbrueckii as starter culture for alcoholic fermentation (AF) is a current trend for enhancing the quality of red wines. As red winemaking usually requires subsequent malolactic fermentation (MLF), the compatibility of this yeast and Oenococcus oeni is a key factor for a successful fermentative process. In this work we study the interactions of T. delbrueckii and O. oeni in wines from grapes with different degrees of maturity. The results showed higher total polyphenolic index (TPI) values in T. delbrueckii wines. Moreover, the aromatic characteristics were improved in these wines, compared to the wines inoculated only with Saccharomyces cerevisiae. There was also a reduction in some inhibitor compounds for O. oeni, for instance medium chain fatty acids, as a result of the fermentation with this non-Saccharomyces. Overall, the use of T. delbrueckii resulted in better MLF performances.

Application of Microwaves as an Advanced Technique for the Development of Sherry Vinegar Macerated with Pineapple

This work proposes the elaboration of a product based on the maceration of Sherry Vinegar together with pineapple in order to extract certain volatile compounds that can be found in pineapples, giving a final product with new organoleptic properties and increased polyphenolic content. Maceration trials were carried out with the application of microwaves and ultrasound, which reduced the maceration time from the traditional three-day solid-liquid maceration to just a few minutes. In addition, through maceration, the total polyphenol index increased significantly with respect to unmacerated vinegar, and the volatile profile of the vinegars was significantly modified. The tasting scores placed the pineapple macerated vinegar sample obtained by traditional maceration in the first place with respect to pineapple aroma; however, the microwave extraction samples were better rated in terms of overall quality. It can be concluded that the application of extracting energies, such as microwaves, can be a viable alternative for the production of sherry vinegar macerated with pineapple.

High-Resolution Drone-Acquired RGB Imagery to Estimate Spatial Grape Quality Variability

Remotesensing techniques can help reduce time and resources spent collecting samples of crops and analyzing quality variables. The main objective of this work was to demonstrate that it is possible to obtain information on the distribution of must quality variables from conventional photographs. Georeferenced berry samples were collected and analyzed in the laboratory, and RGB images were taken using a low-cost drone from which an orthoimage was made. Transformation equations were calculated to obtain absolute reflectances for the different bands and to calculate 10 vegetation indices plus two new proposed indices. Correlations for the 12 indices with values for 15 must quality variables were calculated in terms of Pearson’s correlation coefficients. Significant correlations were obtained for 100-berries weight (0.77), malic acid (−0.67), alpha amino nitrogen (−0.59), phenolic maturation index (0.69), and the total polyphenol index (0.62), with 100-berries weight and the total polyphenol index obtaining the best results in the proposed RGB-based vegetation index 2 and RGB-based vegetation index 3. Our findings indicate that must variables important for the production of quality wines can be related to the RGB bands in conventional digital images, potentially improving and aiding management and increasing productivity.

Exploring young consumers’ attitudes and emotions to sensory and physicochemical properties of different red wines

To gain deeper understanding on young consumers’ attitudes and preferences to wines is needed to connect wine industry with the youth. The aims of the present study were (i) to define ‘trendy wine’ for young consumers and (ii) to identify chemical drivers of liking in red wines for the youth. The study was divided in two phases: phase I explored young consumers’ attitudes towards wines using an online survey, and phase II studied the relationship between hedonic and emotional responses elicited by 12 red wine samples and their physico-chemical characteristics. Consumers’ responses and physico-chemical data were related using Principal Component Analysis (PCA). Results of the online survey showed that trendy wines were associated to: sparkling, soft, fresh, fruity, sweet, light, and balanced wines. Also, young consumers reported that, although flavor was considered the most important attribute, price and Protected Designation of Origin could be valuable attributes. PCA results of phase II showed that wines with a lower ratio [total polyphenol index/polysaccharides] were more liked and elicited more positive emotions than wines with higher total polyphenol index, color intensity, volatile acidity, and alcohol content. Liking and positive emotions were positively related to higher Odor Activity Values of the volatile compounds from the organic acids group. The presence of benzenoids and lactones, and the lower presence of terpenoids & norisoprenoids were associated with negative emotions. In conclusion, red wines should be soft (described as lower ratio [total polyphenol index/polysaccharides]), and have floral, and fruity aromas to better connect with young consumers.

Chemical content and sensory changes of Oloroso Sherry wine when aged with four different wood types

Oloroso Sherry Wine is a fortified Sherry wine obtained by oxidation and ageing in American oak barrels of 500 L–600 L. In this work, the study of the suitability of other types of woods for the ageing of these wines was carried out. To compare the characteristics of the alternative woods, an oloroso wine was aged in four groups of 16 L barrels made of French oak, Spanish oak, chestnut, as well as American oak as control, with intense and medium toasting. Phenolic and furanic compounds, organic acids, volatile compounds, color characteristics, total polyphenol index and sensory analysis of wines aged for two months were analyzed. The results confirmed that the aged samples could be differentiated on the basis of their chemical composition, and that the use of alternative woods to age oloroso Sherry wines, and the level of wood toasting, had the potential to provide products with specific differences to the traditional aged in American oak. Furthermore, the organoleptic characteristics of these alternative wines were valued above a standard Sherry wine.

Assessment of Bioactive Phenolic Compounds and Antioxidant Activity of Blackberry Wines.

Blackberry wine is a natural source of bioactive phenolic compounds that have profound antioxidant potential. The objectives of the present research were to assess the phenolic compounds and antioxidant activity of blackberry wines (BW), and to use the chemometric analysis to differentiate among the two groups of samples, i.e., conventional and organic. Fifteen BW samples were analyzed for their total polyphenol index, total polyphenols, total flavonoids, total tannins, total monomeric anthocyanins and antioxidant activity by the appropriate spectrophotometric methods. The concentrations of individual phenolic acids (gallic acid, chlorogenic acid, caffeic acid, p-coumaric acid and cinnamic acid) and trans-resveratrol were determined by high-performance liquid chromatography. A comparison between the two groups of investigated BW samples revealed a statistically significant difference in the concentration of caffeic acid and p-coumaric acid, both being higher in the organic BW samples. Furthermore, the results showed a series of statistically highly significant relationships between the analyzed constituents (caffeic acid and p-coumaric acid). The antioxidant activity of the investigated wines was proportional to the concentrations of bioactive phytochemicals.

Colour Evaluation of Pinot Noir and Merlot Wines after Malolactic Fermentation Carried out by Oenococcus oeni and Lactobacillus plantarum Patagonian Native Strains

Malolactic fermentation is a complex process that involves many reactions aside from the decarboxylation of L-malic acid. But we still have only glimpses of that complexity. It is not clear if the phenolic composition and colour are affected by malolactic fermentation and, if so, to what extent. So, the aims of this study were: 1) to evaluate the behaviour of native Patagonian strains of Oenococcus oeni and Lactobacillus plantarum in two wine varieties, and 2) to analyse the effect of malolactic fermentation on the colour of these wines. Our results show that the survival of bacteria and L-malic acid decarboxylation is different depending on the lactic acid bacteria strain employed and the wine variety. In addition, we found that O. oeni can survive in wine even when L-malic acid is not being consumed. We found some correlations between MLF and colour-related parameters in Pinot noir but not for Merlot. In fact, some of the colour-related parameters measured in Merlot (total polyphenolic index, colour intensity, hue, as well as the CIELAB parameters) were affected even when L-malic acid was not being consumed.

Wild grapevine (Vitis sylvestris C.C.Gmel.) wines from the Southern Caucasus region

Grapevine domestication took place in the Caucasus area known as the Cradle of Viticulture, within or near the geographical area known as the Vavilov Triangle. The phytogenetic resources of Vitis sylvestris C.C.Gmel. have been previously collected and characterized, but the study on micro vinifications of wild grapevines from the Caucasus is new.In the present document, seven grape samples from female individuals of wild grapevine growing in the South Caucasus region were investigated to assess their oenological profile.Wine samples were obtained from the grapes collected from various populations of Armenia, Azerbaijan and Georgia in October 2013 and fermented by the native yeasts.Parameters determined in the wines were, among others, concentration of ethanol (3.63% – 10.15%), pH (3.30 – 4.20), total acidity (1.2 – 10.7 g/L of tartaric acid), total polyphenol index (1.81 – 89.8), and color intensity (2.59 – 20.76). This wide range values is due to the different environmental conditions, the level of ripeness of harvested grapes and their genetic diversity. These data were compared with those obtained in micro vinifications of wild grapevines in Western Europe and wines of several international cultivars.The results of our research demonstrated, that the must of wild grape could be used to improve traditional wines giving to them more coloration.

Application of a grape surface majority pectinolytic species, Aureobasidium pullulans, to low-temperature red winemaking: development and stability of wine colour

ABSTRACT Low-temperature red winemaking is mainly used for enhancing the wine aroma; however, colour and phenolic extraction is reduced under this condition. This work evaluated the effects of the pectinolytic strain Aureobasidium pullulans GM-R-22, belonging to the most abundant species in grape surface and the greatest pectinase producer, applied to pre-fermentative cold maceration and low-temperature fermentation, on anthocyanin extraction, chromatic and technological properties, also on sensory attributes of Malbec wines. A. pullulans demonstrated to survive in grape juice and first days of fermentation, and high levels of pectinase activity were detected in GM-R-22 vinifications. GM-R-22 wines exhibited higher total anthocyanins, total polyphenolic index and colour intensity (CI), as well as filtration times 30% lower. GM-R-22 wines showed an increase in monomeric anthocyanins during fermentation and higher polymeric pigments at 9 months of bottle storage, suggesting a greater stability in wine colour. From a sensory standpoint, GM-R-22 wines obtained higher scores for CI and violet hue than their respective controls, improving aroma and equilibrium. This study proved that it is feasible to use this unconventional microorganism in oenology to produce pectinases during the low-temperature winemaking process to attain wines with similar or better chromatic properties to those of traditional wines.

DETERMINACIÓN DE POLIFENOLES TOTALES Y ACTIVIDAD ANTIOXIDANTE DE EXTRACTO DE SEMILLAS DE UVAS RESIDUOS DE LA PRODUCCIÓN DE PISCOS

Las uvas pisqueras son 8 variedades conocidas de Vitis vinifera de las cuales se obtiene el pisco. Durante el proceso de producción del pisco se desprenden del fruto subproductos como las semillas, hollejos y otros; las semillas últimamente están cobrando especial importancia debido a su alto contenido en polifenoles y sus propiedades antioxidantes. Existen diversos métodos para la obtención de extractos y con el fin de obtener extractos con el mayor contenido de polifenoles posibles, en este estudio se hace uso de un baño ultrasonido con un sistema de solvente etanol: agua: ácido acético (90/9,5/0,5), el cual luego se lleva a sequedad en un evaporador rotatorio. Se determinó el índice de polifenoles totales encontrándose entre 402 a 84/g de semilla, índice de compuestos flavonoides de 9 a 42/g de semilla; la actividad antioxidante por el método de DPPH expresado como IC50 entre 0,184 a 0,858 mg de extracto y por el método FRAP expresado como mM equivalente de trolox de 0,298 a 1,178 mg de extracto de las distintas variedades, respectivamente. El resultado obtenido nos permite proyectar la recuperación de estos residuos como posibles sustancias nutracéuticas.

Evolution of the Phenolic Fraction and Aromatic Profile of Red Wines Aged in Oak Barrels.

Various changes occur in red wine during aging in oak barrels. Among these, the variation of the polyphenolic fraction and the transfer of aromatic compounds to the wine from oak wood are of great importance. The aim of the present work is to compare the chemical composition of wines aged in different new oak barrels with similar commercial denominations. During 8 months, the total polyphenol index (TPI), color parameters, anthocyanins and pyranoanthocyanins, and wood aromatic compounds were periodically evaluated. The measurement of the TPI and color parameters was similar in all wines, but significant differences were found in total anthocyanin and vitisin content and in certain aromatic compounds belonging to volatile phenols, furanic compounds, and phenolic aldehydes. The results obtained indicate the need for the winemaker to carry out preliminary tests in order to be able to choose the wood that best suits the sensorial profile of the wine.

Variability in the potential effects of climate change on phenology and on grape composition of Tempranillo in three zones of the Rioja DOCa (Spain)

Abstract The objective of this research was to analyse the potential effect of climate change on phenology and berry composition of the variety Tempranillo cultivated in areas of the Rioja DOCa (Spain) with different climatic characteristics. Three zones were selected within the DOCa, which were located at elevations between 325 and 650 m a.s.l. Phenology and the evolution of berry composition during ripening was analysed for the period 2008-2018. This information included the dates of the phenological stages H (separated flowers), M (veraison) and maturity (based in a fixed value of the probable alcoholic degree (PVAD)) and as well as pH, total acidity, malic acid, total anthocyanins, total polyphenols index and colour intensity, recorded in two plots at each location. The climatic conditions recorded during the period of study were evaluated from meteorological stations located close to the vineyards. The average predicted changes in temperature (maximum and minimum) and in precipitation, under two Representative Concentration Pathway (RCP) emission scenarios (RCP4.5 and RCP8.5) and simulated using an ensemble of 10 models were analysed by 2050 and 2070 for each zone. These data were obtained using the MarkSim™ DSSAT weather file generator. The relationship found at present between climate characteristics and the phenology and grape composition were considered in order to project the changes under climate change. The results indicated projected increase of temperature higher in the warmer than in the cooler area, and changes in average precipitation, which although being small will contribute to increase water deficits. The results predict that all evaluated phenological stages will suffer an advance, which will be higher for veraison and maturity than for the stage related to flowering. The advance of the stage H, M and maturity for the three zones by 2050 could be up to 5, 8, and 12 days, respectively under the RCP4.5 emission trajectory, and up to 8, 12 and 15, respectively under the RCP8.5 emission trajectory. The predicted advances indicate that the differences in timing that already exists between zones will be maintained or even increase, which will imply reaching maturity in the second half of August in the warmer area and in earlier September in the coolest one. Grape composition could also suffer changes, reaching the required PVAD earlier with a decoupling between anthocyanins and sugars and with lower acidity caused by the increase of temperatures.

Nanofiltration process as non-thermal alternative to thermovinification in Pinot noir winemaking

This study aimed to evaluate the potential of membrane technology to improve polyphenol extraction during red wine alcoholic fermentation of the Pinot noir grape variety. The effect of adding permeate obtained from saignée nanofiltration onto grape pomace during alcoholic fermentation on wine phenolic extraction was investigated. The process consisted in the addition of nanofiltration permeate (NF) from saignée onto grape pomace in three different steps during alcoholic fermentation, corresponding to volumic mass of 1.060, 1.030 and 1.000 g.cm-3 (treatments called NF1060, NF1030 and NF1000, respectively). This innovative extraction strategy was compared with the extraction by thermovinification (TV), a conventional method used to increase anthocyanin extraction in red winemaking. All trials were performed at microvinification scale (30 kg of grapes, in duplicate). Total polyphenol index, color intensity and total anthocyanins were measured during fermentation. In the finished wines, after malolactic fermentation, tannins, HCl index, gelatin index and dialysis index were determined and a sensory evaluation was made by an expert panel. The results show that nanofiltration treatments were able to extract the same amount of total polyphenols and reach the same color intensity as thermovinification. A higher extraction of anthocyanins (around 25 %) was obtained using NF1030 and NF1000, and a higher content of tannins was found in NF wine than TV wine, with a higher degree of polymerization in NF1060 and NF1030. The perceived astringency reflected the gelatin index values, with NF1030 wine the least astringent. The wine tasters agreed on a higher sensory appreciation for NF wines, especially NF1030. The results obtained in this study are a good incentive to promote research on nanofiltration processes as a non-thermal alternative to modulating polyphenol extraction during red wine fermentation.

PEF-dependency on polyphenol extraction during maceration/fermentation of Grenache grapes

Application to different electric field strengths (E) and specific energies (W) with the pulsed electric fields (PEF) technology on the rate of extraction of phenolic compounds during maceration/fermentation of Grenache grapes was studied. A response surface model between the total polyphenol index extraction rate (TPI) and the E and W of the PEF treatments was established, which permitted the determination of PEF processing conditions to achieve a certain TPI. To achieve a TPI of 50, treatments ranged from high intensity and short time (8 kV·cm−1 and 45 μs) to low intensity and long time (1 kV·cm−1 and 2800 μs) applying an optimum W of 4 kJ·kg−1 in all cases. The application of these PEF treatments reduced maceration time by a rate of 25 to 37% with respect to the untreated grape. Quality characteristics (color intensity, tannins, and total anthocyanins) were neither affected after fermentation nor after 12 months aging in bottles.