Characterization of soluble dietary fiber from R. oligosporus-fermented sweetpotato residues and its effects on the quality attributes of noodles
Yunyi Jin, Yi Zhao, Fidelis Azi, Wenjing Xue, Jiyu Cheng, Jiacheng Qian, Xinyi Tang, Dongchao Xie, Jian Zheng, Peng Jin, Liqing Yin
Abstract
Sweetpotato residues, a dietary fiber-rich by-product of starch industry, has not been fully exploited. The objectives of this study were to use R. oligosporus fermentation to enhance the utilization of sweetpotato residues in terms of functional property in vitro and application potential of its soluble dietary fibers (SDF). Our findings indicated that the initial flat and dense microtopography of SDF were transformed into a rough and porous state after fermentation. The particle size and molecular weight of SDF were significantly reduced following fermentation, along with changes in monosaccharide composition. Fermentation also induced a significant improvement in the in vitro functional activities of SDF, including water solubility, swelling capacity, oil-holding capacity, glucose adsorption capacity, glucose dialysis delaying capacity, α-amylase inhibition and antioxidant activity. Adding 1%-3% (w/w) F-SDF improved dough viscoelasticity and noodle cooking qualities without affecting sensory scores. The in vitro starch digestion of wheat noodles was obviously restrained by F-SDF via converting the digestible starch into the non-digestible fraction, thereby significantly lowering the glycemic index of wheat noodles. In conclusion, sweetpotato residues SDF bioprocessed by R. oligosporus fermentation showed high functional properties especially in reducing the postprandial blood glucose elevation ability of wheat noodles.