Micronization and granulometric fractionation improve polyphenol content and antioxidant capacity of olive pomace

Abstract

This study was aimed to evaluate the effect of micronization of granulometrically fractioned olive pomace (OP) on the content of extractable polyphenols (EPP), non-extractable polyphenols (NEPP) and its antioxidant capacity. Crude OP was separated in 2-mm sieve, resulting in two fractions: F1 (> 2 mm) and F2 (< 2 mm). F2 had higher content of ash, fat, soluble dietary fiber, EPP, hydrolyzable tannins (HT) and condensed tannins (CT) than F1. F1 and F2 fractions were defatted and submitted to a micronization process using a factorial design 22 (variables: rotational speed and milling time) with EPP as response. The optimal micronizing conditions, 500 rpm/24.8 min for the F1 and 500 rpm/16 min for the F2, reduced particle size to around 30 μm. Micronization increased the content of EPP and HT in F1 and F2. Granulometric fractionation and micronization were effective to increase EPP content and antioxidant capacity of OP.