Extraction of phenolic compounds from red grape marc for use as food lipid antioxidants

Grape marc resulting from red winemaking was extracted with a mixture of ethyl acetate and water in order to obtain its phenolic compounds with a view to their use as food lipid antioxidants. Crushed and uncrushed marcs were extracted for 5, 10, 20 and 30 min in order to determine the minimum time required for ensuring maximal extraction of phenols. The results reveal a higher extraction of these compounds by the ethyl acetate acting on crushed marc, so the cost of this last operation can be largely compensated. The antioxidant lipid activity of the phenolic compounds of this extract was determined by using the Rancimat method on refined olive oil, and compared with the induction periods of BHT, BHA, propyl gallate and pure standards of those phenols identified in the above mentioned organic extract. In this test, the phenols of the extract show a lower antioxidant activity than the synthetic food antioxidants, although close to that of BHT, mostly as a result of its catechin content. ©