Correlations between Total Antioxidant Capacity, Polyphenol and Fatty Acid Content of Native Grape Seed and Pomace of Four Different Grape Varieties in Hungary.

Éva Szabó,Gábor Szilágyi,Ágnes Bóna,Kristóf Csepregi,László Kőrösi,Tamás Marosvölgyi,László Márk,János Schmidt

doi:10.3390/antiox10071101

Abstract

Grape pomace is a valuable source of various bioactive compounds such as plant-derived polyphenols and polyunsaturated fatty acids (PUFAs). The commercial demand of grape skin and seed powders as nutraceuticals is still growing. However, no distinction is currently made between unfermented native grape seed and grape seed pomace powders regarding their antioxidant activities. Our aim was to find the relationship between the polyphenol and fatty acid content as well as the antioxidant capacity of native and fermented grape seeds of four different grape varieties harvested in the Villány wine region. According to our results, none of the three investigated polyphenols (resveratrol, rutin, quercetin) could be detected in native grape seed samples in correlation with their significantly lower total antioxidant capacities compared to fermented seed samples. Pinot Noir (PN) grape seed pomace samples with the highest resveratrol and oil content showed significantly higher total antioxidant capacity than Cabernet Sauvignon (CS), Syrah (S) and Blue Portugal (BP) samples. Based on the statistical analysis, positive correlation was found between the fatty acid content and the resveratrol concentration in the pomace samples of different grape varieties. In contrast, rutin concentrations were negatively proportional to the fatty acid content of the fermented samples. No significant correlation was found considering the quercetin content of the samples. According to our findings, grape pomace seems a more promising source in the production of nutraceuticals, since it contains polyphenols in higher concentration and exerts significantly higher antioxidant activity than native grape seeds.

Highlights

IntroductionThe demand for natural plant-based antioxidants promotes the production of wide varieties of nutraceutical products
Considering the resveratrol content of the analyzed grape seed pomace samples, the highest concentrations were detected in the Pinot Noir (PN) samples, while Blue Portugal (BP), Cabernet Sauvignon (CS) and S samples contained significantly lower levels of resveratrol
The absence of resveratrol, rutin and quercetin in native grape seed samples suggests that the process of fermentation may exert a strong impact on the polyphenol content of grape seeds

Summary

Introduction

The demand for natural plant-based antioxidants promotes the production of wide varieties of nutraceutical products. Bioactive polyphenols present in the skin and seeds of grapes occur in wine and even in grape pomace after winemaking (fermentation) [1]. As a relatively inexpensive and abundant source of antioxidants, is commercially available in a form of dietary supplements (powders, tablets, capsules), providing an alternative source of polyphenol intake avoiding wine consumption. No difference is made so far between native grape seed and grape pomace products considering their antioxidant effect. The latter seems a more promising raw material in the production of nutraceuticals

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