Unripe Grape Research Articles

Substitution of additives in horseradish sauce: technological strategies and efficacy

An additive-free horseradish sauce was produced by replacing citric acid and sulfites, commonly used as acidifying, and antimicrobial/anti-browning agents, respectively. Unripe grape juice was used as acidifier, while steam blanching was applied to inactivate horseradish peroxidase (HRP) to avoid browning. Unexpectedly, the heat treatment inactivated myrosinase, responsible for the release of the irritating allyl isothiocyanate from sinigrin's hydrolysis, causing undesired loss of pungency. To restore it, mustard seed powder was added as an ingredient naturally rich in myrosinase. The inactivation of HRP and restoration of myrosinase were evaluated through spectrophotometric measurements of HRP and chromatographic analysis of glucose, a reaction product of myrosinase. The experimental sauce, obtained by adding basic ingredients to horseradish, was stabilized through pasteurization and subjected to sensory analysis and colorimetric evaluation. An additive-free and sustainable horseradish sauce was obtained, using mustard seeds and exploiting thinned bunches as by-products instead of wasting them.

Immunostimulatory effects of dietary verjuice (Vitis vinifera) on immune response and transcription of immune-related genes in juvenile rainbow trout (Oncorhynchusmykiss)

The development of green aquaculture practices has led to the supplementation of fish diets with natural immunostimulants such as organic acids. This study aimed to assess the dietary effects of verjuice (VJ; unfermented unripe grapes; Vitis vinifera) on hematological parameters, skin mucosal immunity, transcriptional immune responses, and antibacterial serum activity against Aeromonas hydrophila in rainbow trout. The fish (51.0 ± 2.4 g) were randomly distributed into 15 tanks and fed ad-libitum thrice daily with diets containing different levels of VJ including 0 (control; VJ-0), 3 (VJ-3), 6 (VJ-6), 9 (VJ-9), and 12 (VJ-12) mL/kg VJ for 56 d. Results showed that immuno-hematological parameters (total white blood cells, neutrophils, and monocytes) were improved in VJ-added groups (P < 0.05). In addition, dietary VJ (9 mL/kg) modulated serum immunological parameters. Skin mucus immunology exhibited a notable increase in alkaline phosphatase, lysozyme activity, alkaline protease, total protein, total immunoglobulin, and esterase levels in VJ-9 group compared with those in the control group (P < 0.05). The mRNA expression of interleukin-1β, interleukin-6, interleukin-8, and immunoglobulin M were significantly higher in VJ-9 group than in the control (P < 0.05). Furthermore, the results of the antibacterial evaluation showed that A. hydrophila growth was significantly inhibited in the serum samples from VJ-3 to VJ-9 groups after the 56th day and in all VJ-treated groups after the 70th (P < 0.05). In conclusion, dietary VJ is a novel immunostimulant and the optimal dietary supplementation level of 6.65–7.46 mL/kg can effectively improve immune responses in rainbow trout.

Screening and Characterization of Phenolic Compounds from Selected Unripe Fruits and Their Antioxidant Potential.

The food sector's interest in sustainability and the demand for novel bioactive compounds are increasing. Many fruits are wasted every year before ripening due to various climatic conditions and harsh weather. Unripe mangoes, grapes, and black lemons could be rich sources of phenolic compounds that need to be fully elucidated. Using fruit waste as a source of bioactive chemicals has grown increasingly appealing as it may have significant economic benefits. Polyphenols are beneficial for human health to inhibit or minimize oxidative stress and can be used to develop functional and nutraceutical food products. In this context, this study aimed to characterize and screen unripe mangoes, grapes, and black lemons for phenolic compounds using LC-ESI-QTOF-MS/MS and their antioxidant activities. Unripe mangoes were quantified with higher total phenolic content (TPC, 58.01 ± 6.37 mg GAE/g) compared to black lemon (23.08 ± 2.28 mg GAE/g) and unripe grapes (19.42 ± 1.16 mg GAE/g). Furthermore, unripe mangoes were also measured with higher antioxidant potential than unripe grapes and black lemons. A total of 85 phenolic compounds (70 in black lemons, 49 in unripe grapes, and 68 in unripe mango) were identified, and 23 phenolic compounds were quantified using LC-MS/MS. Procyanidin B2, gallic acid, epicatechin, caffeic acid, quercetin, and chlorogenic acid were measured with higher concentration in these selected unripe fruits. A positive correlation was found between phenolic contents and the antioxidant activities of unripe fruits. Furthermore, chemometric analysis was conducted to validate the results. This study will explore the utilization of these unripe fruits to develop functional and therapeutic foods.

Using abandoned unripe grape resources to solve the low-acid problem in the northwest wine region of China

Low acid is the main defect in the northwest wine region of China in recent years. The fermentation of unripe grape (UG) and wine grapes with low acid contents was carried out. Compared with control group (CK), the addition of UG addressed the core flaw that low acid grape bring to wine firstly, it significantly increased titratable acid, tartaric acid and malic acid while significantly decreasing alcohol and volatile acids in wine. Secondly, UG significantly improved wine color, the color parameters a*, b*, C* and L* were significantly increased to different degrees. At the same time, the addition of UG significantly improves other qualities of wine, including the phenolic substances and antioxidant capacity of wine. In addition, adding UGJ2% significantly improved the sensory quality, and pleasant volatile substances such as phenethyl alcohol, ethyl hexanoate, ethyl butyrate and isoamyl acetate were significantly increased, giving the wine more prominent floral and fruity aromas.

Boven de 50ste breedtegraad.

Before the climate changes of the late 20th century, the northern part of the Low Countries was generally assumed too cold and wet for viticulture. However, there is evidence of medieval vineyards and viticulture, for example in the gardens of several castles and noble residences in Holland and Gelre around 1375. This article explores the position, size and nature of one of those late fourteenth century castle vineyards above the 50th parallel and concludes that the reason for planting those vineyards was the production of verjuice – the sour juice of unripe grapes. An apparent contradiction is thereby resolved: climatic conditions might have prevented serious wine production, but not vineyard planting.

Optimization of conventional and ultrasound-assisted extraction of pectin from unripe grape pomace: extraction yield, degree of esterification, and galacturonic acid content

Optimization of conventional and ultrasound-assisted extraction of pectin from unripe grape pomace: extraction yield, degree of esterification, and galacturonic acid content

Upcycling flavanol-rich Chardonnay and Pinot noir grape thinned clusters as potentially functional food ingredients in cocoa-based products.

In California, over 3.4 million tons of wine grapes were crushed in 2020 while every year roughly 20% of the grape mass goes unused. Grape cluster thinning at veraison, a common agricultural practice to ensure color homogeneity in wine grapes, adds to the production costs and generates substantial on-farm loss during grapevine cultivation in which the health-promoting values of thinned clusters (unripe grapes) are usually overlooked. In particular, the health-promoting properties of flavanol monomers, specifically (+)-catechin and (-)-epicatechin, and their oligomeric procyanidins, have been extensively studied in cocoa and chocolate but not so much in grape thinned clusters in recent epidemiology studies. As part of the important agricultural by-products upcycling effort, the current study compared thinned clusters from Chardonnay and Pinot noir, two premium wine grape varieties cultivated in California, to a traditionally Dutch (alkalized) cocoa powder that has been widely used in food applications. Thinned cluster fractions from Chardonnay and Pinot noir grapes grown in the North Coast of California showed much higher concentrations of flavanol monomers and procyanidins, with 208.8-763.5 times more (+)-catechin, 3.4-19.4 times more (-)-epicatechin, and 3.8-12.3 times more procyanidins (by degree of polymerization DP 1-7) than those in the traditionally Dutch cocoa powder. These flavanol-rich thinned clusters that are also considered as plant-based natural products suggested great potential to be functional ingredients in cocoa-based products-which have been ubiquitously perceived as flavanol-rich products by consumers-to enhance their overall dietary flavanol content.

Replacement of SO2 with an Unripe Grape Extract and Chitosan during Oak Aging: Case Study of a Sangiovese Wine.

The aim of this study was to evaluate the chemical, microbiological and sensory characteristics of a Sangiovese wine aged in barrique with the addition of an unripe grape extract (UGE) as an alternative to sulfur dioxide. Three samples were considered: control wine (TQ) with free SO2 of approximately 15 mg/L; sample A with chitosan (100 mg/L) and UGE (200 mg/L); and sample B with UGE (400 mg/L). The results achieved in this work demonstrated that the UGE, either alone or in combination with chitosan, was able to maintain the color characteristics of the Sangiovese wine and its sensory quality. Moreover, the addition of UGE contributed to an early and better stabilization of the color through the formation of polymeric pigments. The microbiological stabilization was comparable to SO2 when UGE was used at 200 mg/L in combination with chitosan. The market survey conducted in the present study confirmed how the use of UGE as an alternative to sulfitation was positively accepted by consumers, who are increasingly attentive not only to the quality of the wines they select but also to the sustainability of the production processes from which they derive and to the fact that they are not harmful to human health.

Use of unripe grape wine as a tool for reducing alcohol content and improving the quality and oenological characteristics of red wines

In Mediterranean viticulture, climatic conditions are the main factors that determine grape composition and wine quality. Global warming is causing an increase in the accumulation of soluble solids in grapes, leading to early harvests that result in wines with high alcohol and low phenolic content and colour intensity. The aim of this research was to determine the effectiveness of mixing wines vinified from grapes with different maturation degrees from two consecutive vintages (2018 and 2019) in order to obtain wines with lower pH, lower alcohol content and higher phenolic compound concentration. The wine obtained after mixing wine from unripe grapes (URG) with second harvest (H2) wines significantly improved the physicochemical, chromatic and phenolic characteristics compared to the first harvest (H1) wine. On the other hand, the URGH2 wine had significantly lower alcohol content and pH and higher titratable acidity than the H2 wine. URGH2 maintained its colour intensity in both years and similar values of anthocyanin and tannin in 2018 compared to H2. All the wines were subjected to sensory analysis and the panelists were able to differentiate the wines in a triangle sensory test; the URGH2 wine was preferred in both years. These results show that the blend of unripe grape with wines from technologically mature grapes to reduce alcohol content and improve wine colour could be a useful tool for mitigating the problems caused by global warming in a warm and semiarid Mediterranean climate.

Evaluating the recovery of bioactive compounds and antioxidant activity of unripe red grape liquid extracts obtained by maceration

This paper evaluates the results of extracting bioactive compounds using modern maceration technology, which transforms food products into a liquid extract, based on the example of unripe grapes and its by-product called verjuice. During the extraction process, the indicators of niacin and pyridoxine remained stable, while pantothenic acid and choline increased significantly. During the extraction, the extraction system produced 712 kg of liquid extract, which was characterized by a high content of phenolic compounds and water-soluble vitamins, as well as a high antioxidant activity compared to the measurement obtained for green juice from unripe grapes. Since the estimated liquid extract yield from 950 kg of crushed immature grapes is 847 kg, the actual liquid extract yield was about 80%. The advantages of the maceration extraction method included avoiding the use of solvents or preservatives, low temperature treatment and little oxidative damage. Besides, it enabled enhancing the extraction yield due to introduction of certain post-extraction steps.

Ecological criteria for a sustainability assessment using the example of the online certification “Nachhaltig Austria” (Sustainable Austria)

The sustainability initiative must not focus on just a few and often ideologically occupied activities in wine production, but must bring about a transformation of all essential activities in the vineyard and cellar into more sustainable production. For this reason, the online tool “Sustainable Austria” has been introduced in Austria since 2015, which now covers around 25% of Austrian wine production and thus allows representative conclusions to be drawn about overall production. The data from 2019 to 2021 were used to evaluate part of the approximately 360 activities for assessing sustainability in vineyards and cellars. In addition to the type of plant protection products, a targeted, efficient and economical plant protection application must be made, which can save up to 40% of plant protection products through the use of tunnel and recycling technology and low-loss spraying technology (application by 60% of winegrowing enterprises). While only 0.6% fungus-resistant grape varieties were planted in 2019, this figure was already 7% in 2021. While 30.5% of vineyards were treated with herbicides in 2019, the area fell to 11.8% in 2021. This trend is continuing and can in any case also be attributed to the advice and awareness-raising provided as part of the certification. Retreat areas for flora and fauna represent important biodiversity-promoting measures. More than 1/4 of the certified vineyards have a biodiversity area of over 10% of the vineyard area, more than half over 5% of the vineyard area. While wine producers prefer biennial and perennial greening at 51.3%, 74.4% of grape producers choose autumn/winter greening. The wine industry's contributions to the achievement of the European Green Deal represent key environmental sustainability objectives. 11 wineries are already energy self-sufficient. The building rating A, A+, A++ and the earth cellar represent the best energy efficiency, which is achieved by more than 2/3 of the Austrian wineries. Furthermore, the share of renewable energy in the wine cellar has increased from 56.3% (2019) to 78.9% (2021). On the other hand, the use of new glass bottles is over 80%, while the refilling rate of glass bottles is only 6%. But the share of lightweight glass was 56.6% in 2021. If it is mentioned in this context that about 50% of the greenhouse gases can be attributed to the glass bottle and the refilling of glass bottles causes 59% less GHG than bag-in-box, a trend reversal for washing and filling used glass must be increased in the future. Cardboard packaging takes the lion's share with around 93%, whereby fortunately the share of packaging that has a recycling share of over 50% predominates with 68%. About 1/4 of the vineyard areas are irrigated, whereby overcrown irrigation is of no importance and only water- saving drip irrigation is used. The average amount of irrigation is 41 mm. An economy-of-scale effect can be seen in the water consumption per litre of wine in the cellar. Water consumption in small businesses with less than 10,000 litres of wine production is around 15 litres, whereas it drops to around 3 litres in businesses with more than 500,000 litres of wine production. Wastewater management is very strictly regulated in Austria and requires additional measures and official obligations for wastewater treatments like neutralisation, sedimentation basins and complete wastewater treatment before discharge amount to about 57% in 2019. The majority (about 2/3) of the grape harvest is harvested by hand. With about 1/3 fractionated harvesting, i.e. multiple selection of ripe and unripe grapes to increase quality, the ambitious quality production is underlined. The use of declarable quantities of allergenic protein-based wine treatment agents, sorbic acid, DMDC and/or lysozyme plays no role at all in Austria. While in 2020 and 2019 the natural or no tartar stabilisation was around 25%, this proportion increased to around 40% in 2021 due to the cold natural weather conditions. About half of the wines are stabilised by adding metatartaric acid, gum arabic, carboxymethyl cellulose or mannoproteins, while about 10 to 15% are stabilised by artificial cooling. Finally, it is concluded that raising awareness about negative sustainability activities and providing information about alternatives has led to a positive sustainability development in the Austrian wine industry and continues to do so.

A Sustainable Approach Based on the Use of Unripe Grape Frozen Musts to Modulate Wine Characteristics as a Proof of Concept

Aiming to develop a sustainable methodology for must acidity correction in winemaking, particularly needed in warm regions, the present study intends to fulfill the circular economy values. Antão Vaz white wines were produced using two different strategies for must acidity correction: (i) the addition of a mixture of organic acids (Mix*) commonly used in winemaking; and (ii) the addition of previously produced unripe grape must (UM*) from the same grape variety. In addition, a testimonial (T*) sample was produced with no acidity correction. For all wines produced, oenological parameters were determined, and both amino acid (AA) content and volatile composition were evaluated. A higher AA content was found in the Antão Vaz T* wine, followed by UM* wines. The volatile profile was also affected, and LDA demonstrates a clear separation of wines with different acidity corrections. Results obtained indicate that unripe grape musts—a vital waste product containing several compounds with important biological activity—can be used to increase musts acidity without a negative impact on wine characteristics. Furthermore, this work also shows that the use of unripe must may be a valuable tool for reducing the alcoholic content of wines.

Characterization of Unripe Grapes (Vitis vinifera L.) and Its Use to Obtain Antioxidant Phenolic Compounds by Green Extraction

Thinning pruning is a process in modern viticulture to improve product quality when grapes are still in the immature fruit stage. Unripe grapes, which are waste, are mostly consumed locally as verjuices to meet domestic demand. This study aims to optimize a more efficient “green” technique for the extraction of total phenolic compounds (TPC) and antioxidant capacity (AC) from three varieties of unripe grape juice by response surface method (RSM) using ultrasound-assisted extraction (UAE). The influence of temperature (25–65°C) and extraction time (5–30 min) on total phenolic content (TPC) and antioxidant capacity (DPPH and CUPRAC) was investigated. In this study, physicochemical properties, mineral composition, phenolic and organic acid components of three different verjuices were also investigated. As a result, the optimal extraction points for extraction time (12 min) and temperature (30°C) were determined. All independent variables were found to be significantly effective on TPC and AC content during UAE. Verjuices are a rich source of antioxidants, phenols, organic acids, minerals, and vitamin C. This study is expected to contribute to the evaluation of unripe grape wastes, which are very rich in bioactive components, and to increase its economic potential by expanding local production, thus contributing to sustainable agri-food processing.

Biomass estimation and characterization of the nutrient components of thinned unripe grapes in China and the global grape industries.

The biomass of thinned unripe grape (TUR) was investigated and estimated in China and the world. In addition, the physicochemical parameters, nutritional and functional components and antioxidant activity of nine TUR and ripe grape fruit (RGF) samples were determined and analyzed. The results showed that about 1695.75 kt TUR was produced in China and as much as 14436.16 kt worldwide, which was closely related to the fruit thinning time. The total sugar and protein contents of TUR were significantly lower than those of RGF (p<0.05), while the organic acids (especially tartaric acid and malic acid) and crude fiber of TUR were significantly higher than those of RGF (p<0.05). Moreover, the total polyphenol, flavonoid, tannin and flavan-3-ols contents of TUR were 4.2-13.5, 3.6-12.3, 4.3-62.8 and 1.5-7.6 times those of RGF, respectively. Meanwhile, the antioxidant capacity of TUR was significantly higher than that of RGF, as well (p<0.05). This study aimed to conduct in-depth research into the nutritional characteristics of TUR, propose the targeted direction for their further investigation and then lay a theoretical foundation from which the research findings could be applied in practice.

Utilization of the basket press method to extract verjuice

In this study, two cylinders were used as the main part of the basket press. Berries were poured into the cylinders and were subjected to compression force. Loading rate, layer height, number of layers, and cylinder diameter were considered operating factors. Force–deformation data were recorded. At the end of each test, the mass of extracted juice was measured. Extraction Yield of Juice (YOP), pomace density, Specific Absorbed Energy by Berries (SAEB), and Efficiency Index of Energy (EIE) were output variables. Analysis of variance and optimization were performed. The operating parameters on YOP and SAEB were effective at a significance level of p-value < .01. Moreover, the EIE was significant under the effect of all inputs at 5%. YOP and SAEB ranged from 23.42 to 43.10% and 192.23 to 255 J kg−1, respectively, for basket 1. The corresponding values for basket 2 were 11.07 to 27.81% and 53.53 to 84.01 J kg−1, respectively. Novelty impact statement The basket press method helps to maintain the quality of the juice because by applying the controlled pressure, the bitter seeds of the unripe grape berries can be prevented from being crushed and the bitterness transferred to the juice. The pressure on the berries was increased to the point that the quality of the extracted verjuice did not decrease. Effects of loading rate, layer height, and the number of layers are significant on the performance and efficiency of the method.

1H NMR and UPLC-HRMS-based metabolomic approach for evaluation of the grape maturity and maceration time of Touriga Nacional wines and their correlation with the chemical stability

Touriga Nacional is a well-adapted Portuguese grape variety in São Francisco River Valley (northeastern Brazil). Nevertheless, it has only been indicated to short-term consumption because of the lack of chemical stability, which is attributed to low grape acidity and incomplete phenolic maturity. Therefore, we used Ultra-Performance Liquid Chromatography coupled High-resolution Mass Spectrometry, Nuclear Magnetic Resonance and chemometrics (PCA and PLS-DA) to evaluate the grape maturity and maceration time on chemical composition of wines from two harvest seasons. Moreover, we investigated how these experimental factors could affect their chemical stability. Grapes maturity showed to be the main effect. Overall, phenolic acids and short-chain organic acids were found to be at higher levels in wines produced with unripe grapes from February and shorter maceration time (p < 0.05). Proanthocyanidins and other flavonoids were increased in wines macerated for longer time using overripe grapes harvested in July. Furthermore, stable wines were made from overripe grapes, which contained more galacturonic acid.

Unripe grapes: an overview of the composition, traditional and innovative applications, and extraction methods of a promising waste of viticulture

Unripe grapes (UGs) are a waste product of grapevine cultivation and an emerging source of several compounds, such as organic acids, phenolic compounds, vitamins and mineral salts, of great economic importance to the pharmaceutical, cosmetic and food industries. Traditionally, products made from UGs, such as verjuice and sour grape sauces, have been used as seasoning or acidifying agents. The health effects of grape compounds are described as anti-inflammatory, cardioprotective, anticancer and antidiabetic, as often demonstrated by both in vitro and in vivo studies. Recently, UGs have received renewed attention because of the innovative potential applications of their extracts in food and beverages for purposes of preservation and enrichment with healthy compounds, or for direct use in the human diet. The aim of this article is to review the composition and properties of UG products and their traditional and innovative application in food and beverages.

Physico‐mechanical properties of unripe grape berries relevant in the design of juicing machine

AbstractTo optimally design post‐harvest handling and processing equipment for unripe green grape berries, it is necessary to determine the physical and mechanical properties of the product. In the current study, dimensional (by image processing), gravimetrical, frictional, and aerodynamic (by image processing) properties of unripe green grape berries affected by storage time (31 days in refrigerator) were investigated. Besides, rupture force, rupture energy, elasticity modulus, toughness, hardness, maximum compressive contact stress, Poisson's ratio (by image processing), and shear modulus in horizontal and vertical loading under different moisture content and loading rate levels were measured. Moreover, to model loading and stress‐relaxation behavior of bulk berries, berries were poured into cylinder and compressed. Effects of cylinder diameter, loading rate, the height of layers, and number of layers on loading and stress‐relaxation behavior were investigated. During storage, as the moisture content decreased from 94.57 to 83.88% (w.b.), dimensions and mass of the berries decreased while bulk density and true density increased. With decreasing the moisture, friction angles on galvanized, iron, and rubber were ranged from 22.43° to 26.73°, from 25.38° to 28.53°, and from 29.7° to 34.2°, respectively. Filling angle of repose ranged from 13.44° to 17.65° and emptying angle of repose ranged from 13.95° to 18.33°. In the mentioned moisture range, terminal velocity increased from 0.202 to 0.275 m s−1, and drag coefficient increased from 0.180 to 0.272. Reducing moisture content and increasing rupture energy of the fruits during storage indicates that berries' juice should be extracted immediately after harvest.Practical ApplicationsUnripe grape berries with a sour taste can be processed into several sour sauce and verjuice products. Therefore, determining the physical properties of unripe grape berries is essential for the design of harvesting and post‐harvesting equipment. The current work aims to determine unripe grape berries' physical and mechanical properties to recognize their relevance in physico‐mechanical processing. Some of the necessary information for designing and manufacturing harvesting and post‐harvesting machines is provided in this research. Thus, the results provided in the present study would contribute to improving juice extractors, sorters, separators, cleaners, storage structures, dryers, aeration equipment, conveyors, pneumatic elevators, and so forth, designed for the unripe grape berries.

Sensory perception and food neophobia drive liking of functional plant‐based food enriched with winemaking by‐products

AbstractThe use of phenol compounds obtained from unripe grapes as antioxidant sustainable food ingredients is challenging due to their specific sensory attributes, such as sourness and astringency. The aim was to evaluate sensory attributes perception and consumers' liking for beetroot purees added with phenols from unripe grapes. According to hedonic responses, consumer clusters were identified and characterized for eating behavioral attitudes. Three hundred two subjects (56% women, 18–60 years old) evaluated sweet, sour, astringency, and overall flavor intensity of and liking for four beetroot puree samples added with increasing phenols concentrations (0–1.93 g/kg). Results showed that liking decreased with increasing phenols. Interestingly, samples with highest phenols concentration, characterized by sourness, and astringency, were preferred by a segment of consumers (39% of the group). This group was characterized by a low food neophobia and tended to have high emotional eating scores compared to consumers preferring samples without or with the lowest amount of extract. These results suggest that the development of functional phenol‐enriched products using winemaking by‐products is challenging due to their sensory properties that negatively influence consumers' acceptance. However, with appropriate segmentation strategies it is possible to identify specific consumer targets who could appreciate these new functional foods.Practical ApplicationsUnripe grapes can be used as a sustainable phenol source for the development of new highly antioxidant foods. Indeed, an addition till 1.9 g/kg, besides improving both the nutritional content of the food matrices, as well as promoting the reuse of winemaking by‐products, could be considered feasible from a sensory point of view. Specifically, new sustainable plant‐based food product, characterized by specific sensory attributes, could be target for specific groups of consumers to foster the transition to the consumption of food products developed using value‐added and sustainable ingredients.

Characterisation of Extracts Obtained from Unripe Grapes and Evaluation of Their Potential Protective Effects against Oxidation of Wine Colour in Comparison with Different Oenological Products.

Unripe grapes (UGs) are a waste product of vine cultivation rich in natural antioxidants. These antioxidants could be used in winemaking as alternatives to SO2. Three extracts were obtained by maceration from Viognier, Merlot and Sangiovese UGs. The composition and antioxidant activity of the UG extracts were studied in model solutions at different pH levels. The capacity of the UG extracts to protect wine colour was evaluated in accelerated oxidation tests and small-scale trials on both red and white wines during ageing in comparison with sulphur dioxide, ascorbic acid and commercial tannins. The Viognier and Merlot extracts were rich in phenolic acids while the Sangiovese extract was rich in flavonoids. The antioxidant activity of the extracts and commercial tannins was influenced by the pH. In the oxidation tests, the extracts and commercial products showed different wine colour protection capacities in function of the type of wine. During ageing, the white wine with the added Viognier UG extract showed the lowest level of colour oxidation. The colour of the red wine with the UG extract evolved similarly to wine with SO2 and commercial tannins. The obtained results indicated that natural and healthy UG extracts could be an interesting substitute for SO2 during wine ageing.