Preparation of Grape Sample

A satisfying method of sample preparation for GC/MS analysis of grape extract and used in several studies (Mateo et al., 1997 Chassagne et al., 2000 Flamini et al., 2001 2006), was proposed by Williams et al. (1982) and Di Stefano (1991). Skins of 100 berries are separated from the pulp and are extracted with 35 mL of methanol for 4h in the dark. Pulp and juice are reunited in a glass containing lOOmg of sodium metabisulfite. 

After homogenization by Ultra-Turrax and centrifugation at 4000g for 10 min, solid parts are washed with 50 mL of water, again centrifuged, and the clear liquid is reunited to the juice. The volume is adjusted to 250 mL by water and the solution is treated with 75 mg of pectolytic enzyme for 4h at room temperature. The sample is centrifuged and kept frozen until analysis. 

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