Structural and physicochemical properties and changes in vitro digestion and fermentation of soluble dietary fiber from tea residues modified by fermentation

The aim of this study was to investigate the structure, physicochemical properties, and changes in vitro digestion and fermentation between unfermented tea residue dietary fiber (UDF) and fermented tea residue soluble dietary fiber (FSDF). The results showed that soluble dietary fiber in FSDF was increased from 2.54 % to 15.65 % after fermentation modification. Monosaccharide composition analysis showed that xylose and glucose accounted for a higher proportion in FSDF. FSDF had smaller particle size, lower crystallinity and higher thermal stability. The water holding capacity, oil holding capacity and water swelling capacity of FSDF were significantly increased. Rheological properties showed that FSDF exhibited higher viscosity and better elastic than UDF. Furthermore, FSDF generated more short-chain fatty acids, and the structure was looser than UDF, which was easier to be utilized by intestinal flora. These findings provided higher value of dietary fiber in tea residue by fermentation modification as functional products.