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Methyl jasmonate (MeJ) is an elicitor that, when applied in the vineyard, can improve grape quality. There are several studies about the MeJ influence on red grape varieties; however, to our knowledge, there is little information about white grape varieties, specifically Tempranillo Blanco. Therefore, the aim of this work is to evaluate the effect of MeJ foliar treatments, carried out at veraison and post-veraison, on the aromatic, phenolic and nitrogen composition of Tempranillo Blanco grapes. The results showed that grape volatile compounds content increased after MeJ application, especially terpenoids, C13 norisoprenoids, benzenoids and alcohols, and, in general, mainly at post-veraison. Regarding phenolic and nitrogen compounds, their concentrations were enhanced after MeJ treatments, regardless of application time. Consequently, MeJ treatment improved grape volatile, phenolic and nitrogen composition, particularly when this elicitor was applied post-veraison. Therefore, this is a good and easy tool to modulate white grape quality. [ABSTRACT FROM AUTHOR]

Methyl jasmonate (MeJ) is an elicitor that, when applied in the vineyard, can improve grape quality. There are several studies about the MeJ influence on red grape varieties; however, to our knowledge, there is little information about white grape varieties, specifically Tempranillo Blanco. Therefore, the aim of this work is to evaluate the effect of MeJ foliar treatments, carried out at veraison and post-veraison, on the aromatic, phenolic and nitrogen composition of Tempranillo Blanco grapes. The results showed that grape volatile compounds content increased after MeJ application, especially terpenoids, C13 norisoprenoids, benzenoids and alcohols, and, in general, mainly at post-veraison. Regarding phenolic and nitrogen compounds, their concentrations were enhanced after MeJ treatments, regardless of application time. Consequently, MeJ treatment improved grape volatile, phenolic and nitrogen composition, particularly when this elicitor was applied post-veraison. Therefore, this is a good and easy tool to modulate white grape quality.

Grape pomace contains high amounts of bioactive compounds, mainly polyphenols, with different concentrations depending on several factors: grape variety, vinification procedures, even within the same cultivar variation may be due to the geographic regions and wine vintage. Therefore, phenolic, antioxidant, macro- and micro-nutritional composition of wine waste (pomace and seed) originating from Lacrima di Morro d'Alba red grape variety and pomace of Verdicchio white variety were evaluated for the first time. LC-MS/MS analysis showed the presence of 32 phenolic compounds. The phenolic profile was different in pomace of both varieties: white grape pomaces showed the predominance of flavan-3-ols, while anthocyanins were predominant in red pomaces. Comparing seeds and pomace of Lacrima di Morro d'Alba, catechin and epicatechin are representative compounds in red grape seeds, while malvidin-3-galactoside and petunidin-3-glucoside are the most abundant compounds in pomace of all wineries. Highest TPC and antioxidant activities determined by UV–vis spectrophotometer were observed in seed samples. High dietary fibers, polyunsaturated fatty acids, minerals and protein contents were observed in all samples. Wine byproducts of both grape varieties appeared to be a good source of phenolic and nutritional compounds; therefore, they could be a cheap alternative for phenolics production and development of new functional foods. [ABSTRACT FROM AUTHOR]

Composition and antioxidant activity of grape seed extract (GSE) obtained from red grape varietes are very well documented, in contrast to the white varietes. This paper presents the results of polyphenols content of ethyl acetate extract of grape seeds, obtained from two white grape varieties, Italian Riesling and Župljanka, and their antioxidant activity on the stable DPPH radical. The influence of the addition of GSE to raspberry juice on the DPPH radical was also examined. Content of total polyphenols in GSEs ranged between 81.6 and 82.8% (w/w), and the contetn of flavan-3-ols between 66.2 and 91.0% (w/w). HPLC results showed that the most abundant components in the extract were (+)-catechin and (-)-epicatechin for both grape varieties. All tested GSEs exhibited good antioxidant activity. IC50 values for the GSEs of Italian Riesling and Župljanka were 0.79 and 0.95 mg sample/mg DPPH radical, respectivelly. Since the GSE of Italian Riesling possesed stronger antioxidant activity, it was used for further experiments. The IC50 value for raspberry juice was 4.18 mg raspberry juice/mg DPPH. The raspberry juice with addition of 0.60 μg/mL of GSE showed antioxidant activity of 39.2%. The same juice with the threefold concentration of vitamin C (1.81 μg/ml) exhibited similar antioxidant activity (33.9%). Antioxidant activity of the same amount of juice without added antioxidants was lower (15.7%). The results showed that the GSE of white varietes could be considered as a good functional food ingredient.

Grape seed extracts (GSEs,) obtained from Italian and Rhine Rieslings, were examined for polyphenolic composition and antioxidant activities using HPLC and ESR spectrometry. The seed extraction was carried out with ethyl acetate and ethanol. The contents of polyphenols, flavan-3-ols and antioxidant activities were found to be higher in ethyl acetate than in ethanolic extracts. IC50 values were 0.1045 mg/mL and 0.0599 mg/mL for the stable DPPH radical in ethanolic and ethyl acetate extracts, respectively. The values for the short-lived OH radical were 0.1989 mg/mL and 0.0362 mg/mL, in the given order. The significant correlations between the antioxidant activities of GSEs and polyphenols were established (P < 0.05). Owing to their antioxidant activities, the cultivars could be used as a source to produce a GSE. [ABSTRACT FROM AUTHOR]