Effect of Drying Methods on Bioactive Compounds and Antioxidant Capacity in Grape Skin Residues from the New Hybrid Variety "BRS Magna".

Gabriela Viana Da Silva,Camilla Fernanda Godinho Da Silva,Marcelo Andrés Umsza-Guez,Walkia Polliana De Oliveira,Cedenir Pereira De Quadros,Ederlan De Souza Ferreira,Bruna Aparecida Souza Machado,Janice Izabel Druzian

doi:10.3390/molecules25163701

Abstract

The effects of the drying process using the conventional oven and freeze-drying on the thermogravimetric profile, proximate composition, color parameters, individual bioactive compounds, and antioxidant activity in the grape residue (skin) were evaluated. Twenty individual phenolic compounds were identified, where a variation in concentration was observed for flavonols, stilbenes, phenolic acids, flavonoids, procyanidins, and particularly anthocyanins (malvidin-3,5-di-O-glucoside of 253.2–536.9 mg/kg) due to the drying process. Drying in a conventional oven caused a decrease of 23% of the total polyphenols. The skin of the BRS magna grape has a high concentration of total phenolic content of 489.5–148.3 mg.GAE/100 g, total anthocyanin content of 124.9–260.1 mg.CE/100 g, and total flavonoid content of 12.7–26.0 mg.QE/100 g. The results of free radical scavenging activity (1.26–4.91 μg/mL, as EC50) and ferric reducing antioxidant power (82.93–184.10 μmol/g of skin as equivalent to Fe2SO4) indicate high antioxidant activity, independently of the drying process applied. It was concluded that, if the application is directed to anthocyanin compounds, the use of lyophilization is recommended. On the other hand, if the interest is in bioactive compounds that exert antioxidant activity, conventional oven-drying can be used.

Highlights

Today, the challenge of the social, economic, and environmental impacts of food waste has become an urgent issue globally
An incipient part of the residues derived from industrial grape processing is used to produce different products, from the process of re-fermentation of beverages and distillation, animal feed, and fertilizers [7]
Some studies have shown the use of grape skins as a supplementary source of phenolic compounds [4] in food products [25], while grape skin extracts can be used in drinks [5]

Summary

Introduction

The challenge of the social, economic, and environmental impacts of food waste has become an urgent issue globally. Molecules 2020, 25, 3701 processing of these residues for the elaboration of new products, used as ingredients [4], improvers of technological-functional properties [5], and for nutritional enrichment [6], which can reduce its negative impacts and obtain products with high added value [7]. In this context, the viticulture industry is included, as it generates a large amount of waste. The wine industry produces millions of tons of waste per year, which represents a waste management issue, both ecologically and economically [8]

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Conclusion