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

The bioaccessibilities of polyphenols and polysaccharides in green tea powders (GTPs) with different particle sizes of 564.24 µm, 74.85 µm, 34.62 µm and 15.10 µm 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 15.10 µm was the largest (4.96 mmol Fe 2+ /g). Both the FRAP and DPPH values after digestion showed a trend of first increasing and subsequently decreasing; 74.85 µm GTP had the largest FRAP (4.11 mmol Fe 2+ /g) and DPPH (156.61 mg VCE/g) values after gastric digestion, and 34.62 µm GTP had the largest FRAP (0.16 mmol Fe 2+ /g) and DPPH (1.43 mg 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.