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Grapes present recognized beneficial effects on human health due to their polyphenolic composition. The grape overproduction together with the wine sales down and the world socioeconomic situation makes the wine grape valorization a promising strategy to give an added-value to this natural product. The objective of the present work was to study the influence of in vitro gastrointestinal digestion on antioxidant capacity and polyphenolic profile of skin and seed extracts of different grape varieties (Tempranillo, Graciano, Maturana tinta and Hondarrabi zuri). After in vitro gastrointestinal digestion, total phenolic content (TPC) of seed polyphenolic extracts decreased significantly for all the varieties. The highest decrease was for Tempranillo going from 108 ± 9 to 50 ± 3 mg / g dry matter (dm). This variety also showed the highest decrease of 90% in antioxidant capacity. However, for all the skin polyphenolic extracts there was an increase in TPC. The highest variation was also for Tempranillo. It varied from 10.1 ± 0.8 to 55.1 ± 0.9 mg / g dm. Among red varieties Tempranillo skin polyphenolic extract showed the lowest undigested anthocyanin content but the highest bioaccessibility index (BI) of 77%. For flavanols, flavonols and procyanidins the seed polyphenolic extracts showed a BI at the intestinal phase between 11% for (+)-epicatechin gallate to 130% procyanidin A2. The results of this study suggest that grape skin extracts and grape seed extracts are a reliable source of bioaccessible antioxidant polyphenols, to be used for the development of antioxidant supplements with specific functionalities depending on the grape variety. [ABSTRACT FROM AUTHOR]

This research explores a novel approach in beer production by incorporating waste materials such as grape seeds and skins, derived from wine processing, into the brewing process. This initiative holds promise for effective waste utilization, advancing craft beer, and utilizing cost-effective raw materials. Experiments explore the integration of grape by-products into beer production, evaluating their impact on polyphenol levels and sensory characteristics. The laboratory and pilot brewhouse trial results revealed a significant increase in the total polyphenol content when 0.6 % grape seeds were added during the boiling process. Specifically, the total polyphenol value doubled, reaching up to 500 mg/l compared to the 250 mg/l found in classical pilsner-type beer. The study indicates that grape seed addition is significantly more effective than grape skin addition under the same conditions, yielding around 1.5 times or more polyphenols. Sensory evaluations revealed a preference for beers supplemented with white grape seeds compared to red grape seeds, providing a unique taste experience with a pleasant grape aroma. Moreover, beers with grape seed additions exhibited elevated levels of specific polyphenolic compounds, particularly catechin and epicatechin. Additionally, the antioxidant capacity of the beer slightly increased with grape seed incorporation and colloidal stability was not negatively affected. [ABSTRACT FROM AUTHOR]

Wine pomace, also mentioned as grape pomace (GP), is a byproduct of the wine industry, containing about 50% grape skins, 25% grape seeds and 25% stems. These wastes are of great value and great potential as a source of biologically active compounds. This opens up new prospects for the rational use of GP in the food industry. It is no coincidence that numerous new technologies for processing these byproducts have recently emerged to create a wide range of diverse new food products by enriching traditional foods with antioxidants, dietary fiber and mineral compounds. The most popular GP processing products are extracts and powders. Powders do not require special storage conditions, and they are highly adaptable, mixing well with other types of food raw materials, especially loose ones. Therefore, they are widely used in such products as bread, cookies, pasta, muffins, etc. Grape powders improve the structure of the dough, slow down the oxidation of fats, for example, in cookies, and increase the nutritional value of flour products. Finally, we will discuss these perspectives on the use of grape pomace as an ingredient in the formulation of flour-containing food products. [ABSTRACT FROM AUTHOR]

Wine pomace, also mentioned as grape pomace (GP), is a byproduct of the wine industry, containing about 50% grape skins, 25% grape seeds and 25% stems. These wastes are of great value and great potential as a source of biologically active compounds. This opens up new prospects for the rational use of GP in the food industry. It is no coincidence that numerous new technologies for processing these byproducts have recently emerged to create a wide range of diverse new food products by enriching traditional foods with antioxidants, dietary fiber and mineral compounds. The most popular GP processing products are extracts and powders. Powders do not require special storage conditions, and they are highly adaptable, mixing well with other types of food raw materials, especially loose ones. Therefore, they are widely used in such products as bread, cookies, pasta, muffins, etc. Grape powders improve the structure of the dough, slow down the oxidation of fats, for example, in cookies, and increase the nutritional value of flour products. Finally, we will discuss these perspectives on the use of grape pomace as an ingredient in the formulation of flour-containing food products.

Featured Application: The interest for green and sustainable utilization of industry by-products, such as grape pomace, is increasing rapidly, and is in line with the recognition of the necessity to protect the environment. Our investigation, mainly focused on natural deep eutectic solvents (NADES), could contribute to further exploitation of these solvents for extraction of biologically active compounds from different plants. Finally, the present study provides profound understanding of antioxidant activity and polyphenol composition of grape seeds and skin, highlighting the quality of some insufficiently investigated Serbian autochthonous varieties and suggesting their broaden use. In the past few years, research efforts have focused on plant exploitation for deriving some valuable compounds. Extraction has been usually performed using petrochemical and volatile organic solvents, but nowadays, increased recognition of environmental pollution has prompted the utilization of green solvents as alternatives. Therefore, the aim of the present study was to exploit deep eutectic solvents (DES) (choline chloride: citric acid and choline chloride: glucose) as solvents for extracting valuable phenolic antioxidants from grapes. Investigation was conducted on ten grape varieties, observing seeds and skin as different matrix. Total polyphenol content (TPC) was determined by Folin-Ciocalteu spectrophotometric microassay. Antioxidant activity was investigated using four different tests and results were combined in a unique Antioxidant Composite Index (ACI) to reveal comprehensive information about this biological activity. Polyphenol compounds were identified and quantified with the aim of HPLC-diode array detector (DAD). Overall results support that DES (particularly choline chloride: citric acid) were comparable to conventional solvent, and in most cases even outperformed acidified aqueous ethanol (concerning extraction efficiency and antioxidant activity). Regardless of varietal distinctions, grape seeds have higher antioxidant capacity compared to grape skin, and such findings are according to their phenol compound concentrations. [ABSTRACT FROM AUTHOR]

Grape pomace is one of the most abundant solid by-products generated during winemaking. A lot of products, such as ethanol, tartrates, citric acid, grape seed oil, hydrocolloids, bioactive compounds and dietary fiber are recovered from grape pomace. Grape pomace represents a major interest in the field of fiber extraction, especially pectin, as an alternative source to conventional ones, such as apple pomace and citrus peels, from which pectin is obtained by acid extraction and precipitation using alcohols. Understanding the structural and functional components of grape pomace will significantly aid in developing efficient extraction of pectin from unconventional sources. In recent years, natural biodegradable polymers, like pectin has invoked a big interest due to versatile properties and diverse applications in food industry and other fields. Thus, pectin extraction from grape pomace could afford a new reason for the decrease of environmental pollution and waste generation. This paper briefly describes the structure and composition of grape pomace of different varieties for the utilization of grape pomace as a source of pectin in food industry.

The antioxidant activity and the tocopherol and polyphenol contents of organic grapevines residue were analyzed after Soxhlet extraction of grape seeds and skin with ethanol and petroleum ether. The highest antioxidant activity was determined for the ethanol extract of the seeds and was 58.65 µM Trolox/mg, which was four times higher than for the ethanol extract of the skin at 14.24 µM Trolox/mg. It was comparable to that of the alpha-tocopherol (62.28 µM Trolox/mg) and butylated hydroxyanizol (69.55 µM Trolox/mg). A concentration of 29.5 µg/mL ethanol seed extract was needed to decrease the initial DPPH radical concentration by 50%. The high antioxidant activity was because of the high tocopherol (402.28 mg/kg) and total phenols contents (113.7 gallic acid equivalent (g/kg)) in the seeds. The dominant polyphenol in the ethanol seed extract was coumaric acid (10.97 g/kg). The dominant polyphenols in the ethanol skin extracts were rutin (6.79 g/kg), quercetin (3.75 g/kg), and catechin (3.99 g/kg), which can be used in functional foods to reduce risk factors for several human diseases. [ABSTRACT FROM AUTHOR]

Grape pomace is an agro-industrial by-product from the production of must (grape juice) by pressing whole grapes. In order to evaluate the seeds and skins of the grape pomace, it must first be dried and then separated in a screen machine. The drying of pomace is an important and necessary process for the optimum separation of seeds. The main purpose of this study was to determine the optimum drying process for obtaining high-quality grape seed oil. In this research, open air and solar energy drying methods were compared in terms of water activity, total bacterial and mold-yeast count, along with the chemical and fatty acid compositions of pressed grape residues. Oleic acid and linoleic acid contents ranged from 16.56-16.96% and 71.45-71.96%, respectively. Antioxidant activities ranged from 2.33-2.80 μmol trolox/g. The results showed that the drying methods did not decrease the nutritional quality of grape residues and prevented microbial growth by decreasing water activity to below 0.60. [ABSTRACT FROM AUTHOR]

To develop an efficient method for degradation of grape seed and skin proanthocyanidins polymers into oligomers, an optimized sulphurous acid degradation conditions for grape seed with the temperature of 60 °C, reaction time of 60 min and sample-sulphurous acid ratio of 1:0.2, and for grape skin with the temperature of 40 °C, reaction time of 60 min and sample-sulphurous acid ratio of 1:0.2, were established. Afterwards, HSCCC and prep-HPLC were used to fractionate and isolate individual proanthocyanidin oligomers from the degradation products. Total of ten dimeric or trimeric procyanidins were obtained, and most of them presented high yield (from 0.7 mg to 13.6 mg per run in grape seed and from 0.5 mg to 4.1 mg per run in grape skin) and high purity (over 90%). The proposed method provides a new way for large preparation of oligomeric proanthocyanidins from naturally abundant and wasted polymeric ones. [ABSTRACT FROM AUTHOR]

This paper studies the influence of different maceration times (5, 10 and 20 days) during the elaboration of Monastrell, Syrah and Cabernet Sauvignon wines on the proanthocyanidin composition and sensory characteristics of the resulting wines. Significant differences were found between wines elaborated with different maceration times. The different maceration times affected the qualitative and quantitative proanthocyanidin composition of the resulting wines, the total proanthocyanidin content increasing with the maceration time. The percentage of skin-derived proanthocyanidins was always higher than that of seed-derived proanthocyanidins for all the maceration time assayed, although the contribution of seed proanthocyanidins to wine composition increased for the longest maceration time. However, the study also shows that differences exist between wines elaborated with the same maceration time but with different varieties, indicating the importance of two factors, the initial concentration of grape phenolic compounds and their extractability, on the final concentration of wine proanthocyanidins. In this way, the wines obtained from Syrah had the highest proanthocyanidin content compared with the corresponding wines from Cabernet Sauvignon or Monastrell, even though Syrah grapes presented the lowest proanthocyanidin content in skins and similar seed proanthocyanidin content to Cabernet and Monastrell grapes. [ABSTRACT FROM AUTHOR]

Abstract: Autochthonous grapevine varieties are considered a biodiversity resource in viticulture and an opportunity for Italian sustainable wine production. In this study, the ancient white wine variety Bianchetta Trevigiana, considered part of the agricultural history of the Veneto region, was vinified alone, with or without maceration, in order to better understand its technological and organoleptic characteristics, with the overall objective of valorising and re-evaluating it. The evolution of phenols—compounds that are very important for the organoleptic and technological profile of wine—was monitored during the winemaking process. Results show that contact with grape skins and seeds enhance phenol extraction and produces must and wine with higher concentrations of these compounds. Moreover, it was found that the concentration of flavanols in Bianchetta Trevigiana is similar or even higher than that of red wines. [ABSTRACT FROM AUTHOR]

Abstract: The extracts obtained from skin and seeds of 10 native Tuscan and international Vitis vinifera varieties were evaluated for their antioxidant activity, total phenolic and anthocyanin content and subjected to HPLC–UV analysis to quantify the content of five phenolic constituents of biological interest: catechin and epicatechin in seeds and quercetin, rutin and resveratrol in skin extracts. The antioxidant activity of the extracts and pure compounds was assessed by means of two different in vitro tests: scavenging of the stable DPPH radical and of authentic peroxynitrite (ONOO−). All the extracts showed significant antiradical capacity: Merlot skin was most active towards both radicals. All the five phenols investigated possessed strong antiradical activity. Quercetin, catechin and epicatechin showed maximum activity (respectively, 5.5, 6.7 and 6.8μM, 48.8, 55.7 and 56.7μM). Potential antiradical interactive effects among the five compounds were also investigated and results indicated possible synergy between quercetin, rutin and resveratrol towards ONOO−. The effect was additive for catechin and epicatechin. [Copyright &y& Elsevier]

Grape seeds (GS) and grape skins (GK) are natural sources of polyphenols with featured antioxidant capacity. An experiment was conducted to investigate the effect of these polyphenol sources in diets formulated to contain the same total extractable grape polyphenol content on growth performance, protein and extractable polyphenol digestibility, plasma and meat α- and γ-tocopherol and thigh meat oxidation in broiler chickens. Five experimental diets were formulated: control, control + vitamin E (200 mg/kg), 30 g/kg GS diet, 110 g/kg GK diet, GS + GK diet (a mixture of 24.4 g/kg GS and 13.1 g/kg GK designed to simulate a reconstituted grape pomace). Feeding chickens with 110 g/kg GK reduced (p < 0.001) daily weight gain, worsened (p < 0.001) feed conversion ratio, increased (p < 0.001) non-extractable polyphenol content in the ileum and in the excreta and decreased (p < 0.05) ileal protein digestibility. Regardless of the grape polyphenol source used, the inclusion of grape byproducts in the diets led to an increase of total extractable polyphenol contents in the ileum (p < 0.01) and the excreta (p < 0.001), which resulted (p < 0.001) in a decrease of extractable polyphenol digestibilities. Alpha- and gamma-tocopherol concentrations increased (p < 0.001) in plasma and in seven-day stored meat in birds fed the diet combining GS and GK with respect to the control group. As it happened with the vitamin E supplementation, feeding the combination of GS and GK also reduced (p < 0.001) the concentration of the lipid peroxidation marker (malondialdehyde) in the stored meat of chickens. [ABSTRACT FROM AUTHOR]

Grape pomace is one of the most abundant solid by-products generated during winemaking. A lot of products, such as ethanol, tartrates, citric acid, grape seed oil, hydrocolloids, bioactive compounds and dietary fiber are recovered from grape pomace. Grape pomace represents a major interest in the field of fiber extraction, especially pectin, as an alternative source to conventional ones, such as apple pomace and citrus peels, from which pectin is obtained by acid extraction and precipitation using alcohols. Understanding the structural and functional components of grape pomace will significantly aid in developing efficient extraction of pectin from unconventional sources. In recent years, natural biodegradable polymers, like pectin has invoked a big interest due to versatile properties and diverse applications in food industry and other fields. Thus, pectin extraction from grape pomace could afford a new reason for the decrease of environmental pollution and waste generation. This paper briefly describes the structure and composition of grape pomace of different varieties for the utilization of grape pomace as a source of pectin in food industry. [ABSTRACT FROM AUTHOR]

A bio-electronic tongue has been developed to evaluate the phenolic content of grape residues (seeds and skins) in a fast and easy way with industrial use in mind. A voltammetric electronic tongue has been designed based on carbon resin electrodes modified with tyrosinase combined with electron mediators. The presence of the phenoloxydase promotes the selectivity and specificity towards phenols. The results of multivariate analysis allowed discriminating seeds and skins according to their polyphenolic content. Partial least squares (PLS) has been used to establish regression models with parameters related to phenolic content measured by spectroscopic methods i.e., total poliphenol content (TPC) and Folin–Ciocalteu (FC) indexes. It has been shown that electronic tongue can be successfully used to predict parameters of interest with high correlation coefficients (higher than 0.99 in both calibration and prediction) and low residual errors. These values can even be improved using genetic algorithms for multivalent analysis. In this way, a fast and simple tool is available for the evaluation of these values. This advantage may be due to the fact that the electrochemical signals are directly related to the phenolic content. [ABSTRACT FROM AUTHOR]

Nowadays, the use of plant-based by-products obtained after food processing has gained importance, as these products are nutritious and cheap. The aim of this study was to determine the effects of grape skin and seed powders with different particle sizes (100, 200, 288 and 415 μm) on the texture, sensory, color, and rheological properties of soft candies. According to the results, the particle size of the grape-derived components was a significant factor for the texture parameters, especially hardness, adhesiveness, chewiness, and resilience. In sensory analyses, samples containing grape seed and skin powder with a particle size of 100 and 200 μm received the highest score and particles were not felt by the panelists. Also, the use of grape seed and skin powder decreased the L* value of the soft candies compared to the control group, which was parallel to the decrease in the particle size. It was found that r values of model fitting of rheological data can be correlated with sensory results. In conclusion, it was shown that grape-derived components can be successfully used in the formulation of soft candy if particle size was adjusted below 200 μm. • Particle size of the grape-derived components was an important factor for the texture parameters. • Decreasing in particle size of grape seed and skin powder decreased the L* value of the samples. • r values of model fitting of rheological data can be correlated with sensory results. [ABSTRACT FROM AUTHOR]