Abstract
In this study, the chemical composition, bioactive compounds, minerals, and fatty acid composition of grape pomaces from 10 varieties with seed and skin of several grape varieties were investigated. The varieties Eksikara, calkarasi, and Marcas exhibited significantly (p < .05) higher content of total phenolics (127.18, 138.41, and 147.51 mg/100 g, respectively), with a concomitant higher antioxidant activity (95.47, 96.71, and 98.47%, respectively) than other varieties. The HPLC analysis of phenolic compounds showed that chlorogenic acid, protocatechin, synergic acid, and ferulic acid were major constituents of the varieties. In addition, protocatechin content was significantly (p < .05) higher in Marcas variety (167.84 mg/g) and lower in Buzgulu variety (97.56 mg/g), the chlorogenic acid content was significantly (p < .05) high in Marcas variety (296.51 mg/g) and low in Honusu variety (153.19 mg/g).The analysis of minerals content showed that Fe, P, Zn, and K were major minerals of the varieties. The analysis of fatty acids showed that the dominant fatty acids in varieties were linoleic, oleic, and palmitic acid.
Practical applications The grape industry residues are mostly solid and include stalks, pomace, and liquid filtrate. Bioactive substances extracted from grape residues can add nutritional value to food products for the improvement of dietary pattern and can help in reducing the risk of diseases such as degenerative tract diseases. Grape pomace had high phenolics because of incomplete extraction during the processing of wine. The residues of grape processing such as seeds and pomace constitute a cheap source for bioactive compounds that can be used as supplements or in the production of phytochemicals with economic advantage. In addition, grape pomace is a natural product rich in dietary fiber and polyphenols.