Grape seed pomace as a valuable source of antioxidant fibers

Grape seed pomace is a valuable by-product from winery/oil extraction industries and a potential source of bioactive compounds. Hot water extraction is the most widely used technology for polysaccharide recovery from plant and seed sources. To obtain an antioxidant fiber-rich extract (AFE) from defatted grape seed pomace, seed:water ratio (1:10-1:20) and extraction temperature (70-90 °C) effects on extraction yield, total sugars, total phenolic compounds and condensed tannins were investigated.

The best extraction results were achieved at the highest seed:water ratio and temperature. At these conditions, the extraction yield and total sugar content of the freeze-dried AFE were 100.1 g kg^-1 and 725.3 g kg^-1 , respectively. The AFE presented high total phenolic content (16.2 g GAE kg^-1 ), condensed tannins (515.1 mg CAT kg^-1 ), soluble (219.1 g kg^-1 ) and insoluble fibers (132.4 g kg^-1 ), besides protein (171.1 g kg^-1 ) and ash (152.6 g kg^-1 ). The antioxidant capacity of the AFE was 382.7, 823.7 and 1439.4 μmol Trolox g^-1 for DPPH, ABTS and ORAC methods.

The AFE was shown to be not only an interesting source of fiber with antioxidant capacity, which could become a potential foodstuff, but also an ecofriendly and sustainable alternative to use grape seed pomace. © 2019 Society of Chemical Industry.