Enzyme assited extraction of insoluble-bound phenolics from grape by-products: antioxidant and bioactivity potential

Abstract

Food phenolics are found in the soluble fractions (free and esterified forms) as well as in the insoluble-bound form. We recently demonstrated that, despite the process (juice or winemaking), insoluble-bound phenolics are the major fraction in grape processing by-products (BRS Cora, Isabel, Tempranillo, and Syrah varieties). Furthermore, in another work, we also demonstrated that gamma-irradiation increased the content of insoluble-bound phenolics, probably due to gamma-irradiation induced cross-linking. Insoluble-bound phenolics from grapes inhibited in vitro peroxyl radical induced human LDL-cholesterol oxidation and copper induced DNA strand breakage. However, it has been reported that absorption of insoluble-bound phenolics is limited. Thus, in the present work, enzyme assited extraction will be studied in order to release insoluble-bound phenolics which may be further used as functional food ingredients and/or supplements manufacture. Besides improving the extraction, the process may also lead to chemical structure changes which will likely affect the antioxidant activity of these by-products. Thus, the enzyme assisted extraction will be evaluated for its effect on phenolic profile using HPLC-DAD-ESI-MSn, antioxidante assays and in deactivating seletected enzymes with eventual health benefits. The present study will shed further light on the importance as well as potential use of insoluble-bound phenolics of food plants. Additionaly, the enzyme assisted release of insoluble-bound phenolics may minimize the effect of food processing, such as gamma-irradiation, in inducing insoluble-bound phenolics generation via cross-linking. (AU)