Improved physicochemical and functional properties of dietary fiber from matcha fermented by Trichoderma viride

The low-grade matcha is rich in insoluble dietary fiber. Trichoderma viride was used to increase the soluble dietary fiber to improve its functional properties. The soluble dietary fiber content increased from 6.74% to 15.24%. Pectin, hemicellulose, maltose, d-xylose, and glucose contents increased by 63.35% and 11.54%, 2.18, 0.11, and 7.04 mg/g, respectively. Trichoderma viride fermentation disrupted the dense structure of insoluble dietary fiber, resulting in a honeycomb structure and improving crystallinity by 22.75%. These structural changes led to an improved cation exchange capacity from 1.69 to 4.22 mmol/g, an increase in the inhibitory effect of α-amylase from 47.38% to 72.04%, and a 2.13-fold in the ferrous ion scavenging ability, and the IC₅₀ values of superoxide anion was reduced from 7.00 to 1.54 mg/mL, respectively. Therefore, Trichoderma viride fermentation is an excellent method for improving the quality of dietary fiber in matcha processing by-products.