Influence of some technological practices on the quantity of resveratrol in wine

A study of the effects of some prefermentative and fining practices on the resveratrol concentration in wine was carried out. The trans- and cis-resveratrol contents in a red wine obtained using must hyperoxidation were reduced to about 50% compared with those of control wines; this decrease was greater than that observed for total phenols and catechins. In contrast, sparging the red grapes with SO₂ and ascorbic acid before crushing them resulted in the trans-resveratrol concentration being greater than that of the control wines. Moreover the amounts of trans- and cis-resveratrol in commercial and synthetic wines were determined before and after addition of charcol, polyvinylpolypyrrolidone (PVPP), bentonite, casein, gelatine, and two inert materials, cellulose and diatomaceous earth (kieselgur), used as a filter aid. The results showed that PVPP, charcoal and casein were more effective at removing trans- and cis-resveratrol both in synthetic wine and in commercial wines. In all the wines tested the other fining agents gave a limited decrease (2?–?5%) of trans- and cis-resveratrol. After charcoal and PVPP treatments, significant correlations were observed between the percentage of residual resveratrol and the total phenols in the wines.