Effect of particle size on the bioaccessibility of polyphenols and polysaccharides in green tea powder and its antioxidant activity after simulated human digestion.

Abstract

The bioaccessibilities of polyphenols and polysaccharides in green tea powders (GTPs) with different particle sizes of 564.24µm, 74.85µm, 34.62µm and 15.10µm and their antioxidant activities were investigated using an in vitro simulated gastrointestinal digestion model. The results showed that particle size significantly affected the bioaccessibilities of polyphenols and polysaccharides before and after digestion, except for the bioaccessibility of polysaccharides after gastric plus intestinal (GI) digestion, thus significantly affecting the antioxidant activity of GTPs. Compared with the undigested initial amount, the bioaccessibilities of polyphenols in all GTPs were approximately 59.98-71.00% after gastric digestion and 9.69-15.57% after GI digestion, and the bioaccessibilities of polysaccharides were approximately 71.10-79.51% after gastric digestion and 113.78-190.38% after GI digestion. With the decrease in particle size, the FRAP value of GTP before digestion was significantly increased and that of 15.10µm was the largest (4.96mmol Fe2+/g). Both the FRAP and DPPH values after digestion showed a trend of first increasing and subsequently decreasing; 74.85µm GTP had the largest FRAP (4.11mmol Fe2+/g) and DPPH (156.61mg VCE/g) values after gastric digestion, and 34.62µm GTP had the largest FRAP (0.16mmol Fe2+/g) and DPPH (1.43mg VCE/g) values after GI digestion. This study suggested that the bioaccessibilities of polyphenols and polysaccharides in GTPs and their antioxidant activity can be improved by properly reducing the particle size such that TGPs can exert more beneficial health effects.