The investigation of bioactive compounds of wine, grape juice and boiled grape juice wastes

In this study, bioactive compounds, oil, sugar, fatty acid, and mineral contents of grape wastes (pomace, skin, and seeds) obtained from wine, grape juice, and boilled grape juice production were investigated. Total phenol and tannin contents of grape by-products varied between 31.2 mgGAE/g (molasses skin) and 98.97 mgGAE/g (wine seed); 96.93 mgTAE/g (grape juice pomace) and 138.67 mgTAE/g (molasses pomace), respectively. The highest (377.57 g/kg) and lowest (20.00 g/kg) total sugars were determined in molasses and wine skin wastes, respectively. Epicatechin contents of samples were found between 439.67 mg/kg (molasses skin) and 3,444.57 mg/kg (molasses seed). The lowest and highest linoleic acids were determined in molasses skin oil (40.00%) and grape juice skin oil (51.10%). alpha-Tocopherol contents of wine by-product oils changed between 3.35 mg/kg (seed) and 6.42 mg/kg (pomace). The lowest and highest P contents were determined in molasses skin (17,563 mg/kg) and wine seed (29,634 mg/kg), respectively. Practical applications The residue may represent from 13.5 to 14.5% at the total volume of grapes, and may reach 20%. The most abundant phenolic compound in wine pomace is anthocyanins concentrated in the skin, and flavonols present mostly in the grape seed (56-65% total flavonol). Grape is a phenol-rich plant, and these phenolics are mainly distributed in the skin, stem, leaf, and seed of grape, rather than their juicy middle sections. Skins and seeds of grapes are produced in large quantities by the winemaking industry. These by-products have become valuable raw materials due to their high content of polyphenols, tocols, and other macro- and micronutrients. Seed and skins of grape produced in large quantities by the wine making industry have become valuable raw materials for extraction of polyphenols.