Abstract

PALADINO, Silvia C  and  ZURITZ, Carlos A. Antioxidant grape seed extract (Vitis vinifera L.): concentration, drying and comparison with commercial antioxidants. Rev. Fac. Cienc. Agrar., Univ. Nac. Cuyo [online]. 2012, vol.44, n.2, pp.131-143. ISSN 1853-8665.

The objectives of this work were: 1) to evaluate the processes of concentration and drying of a polyphenolic grape seed extract (Vitis vinifera L.). The processes should be able to preserve the reducing power of the extract; 2) to evaluate the efficiency of the antioxidant obtained by comparison with frequently used commercial antioxidants in a vegetable product susceptible to oxidation, such as apple juice. The single strength aqueous grape seed extract was concentrated at 60°C in a laboratory scale rotary evaporator under vacuum. The phenolic compounds concentration was determined using a modified Folin-Ciocalteu method. The antioxidant activity was evaluated measuring the reducing power by the method of Oyaizu. Apple juice oxidation was determined by the Özoglu method. The concentrated extract obtained was dehydrated by two methods: freeze-drying and foam-mat drying. At the same phenolic concentration, concentrated extracts exhibited greater antioxidant capacity than single strength extracts. Foam-mat dried extracts maintained the same antioxidant capacity than the concentrated extracts. Freeze dried extracts experienced a significant loss of antioxidant activity. The concentrated grape seed extract inhibited the oxidation of apple juice in 31.51%, ascorbic acid in 2.60% and sulfur dioxide in 97.40%.

Keywords : Polyphenols; Grape seed extracts; Antioxidants; Concentration; Drying; Apple juice.

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