Effect of micronization on olive pomace biotransformation in the static model of colonic fermentation

[Display omitted] •Granulometric fractionation (GF) and GF + micronization (GFM) reduce particle size.•GF and GFM increase olive pomace (OP) phenolic compounds (PC) that reach colon.•Tyrosol (tyr) and hydroxy-tyrosol (HT) were the major PC in colonic fermentation.•GFM released more tyr and HT from OP during colonic fermentation.•Only GFM-modified OP samples had oleuropein in the colonic phase of digestion. The effect of granulometric fractionation and micronization of olive pomace (OP) on the biotransformation of phenolic compounds by intestinal microbiota was investigated in vitro. Three types of powdered OP samples were incubated with human feces to simulate colonic fermentation, after a sequential static digestion: non-fractionated OP (NF), granulometrically fractionated OP (GF) and granulometrically fractionated and micronized OP (GFM). GF and GFM favored the release of hydroxytyrosol, oleuropein aglycone, apigenin and phenolic acid metabolites in the first hours of colonic fermentation compared to NF (up to 41-fold higher). GFM caused higher release of hydroxytyrosol than GF. GFM was the only sample to release tyrosol and sustained tyrosol levels up to 24 h of fermentation. Micronization associated with granulometric fractionation was more efficient than granulometric fractionation alone to increase the release of phenolic compounds from the OP matrix during simulated colonic fermentation and can be further studied for nutraceutical purposes.