Preparation and improvement of physicochemical and functional properties of dietary fiber from corn cob fermented by Aspergillus Niger

Abstract

Corn cobs were fermented with Aspergillus niger to produce the high-quality soluble dietary fiber (SDF) with excellent food safety. In this work, the fermentation process was optimized by single-factor test and response surface methodology (RSM) to determine the fermentation conditions (material-liquid ratio 1:30, inoculum concentration 11%, temperature 32 ℃, time 6 d, shaking speed 200 r/min), the SDF yield of corn cob increased from 2.34–11.92% and SDF/TDF reached 19.08%, achieving the requirements of high-quality dietary fiber (SDF/TDF was more than 10%). SEM and FTIR analysis revealed that the fermentation effectively degraded part of cellulose and hemicellulose, resulting in the formation of a loose and porous structure. After fermentation the water swelling capacity, water-holding capacity, and oil-holding capacity of the corn cob SDF were obviously improved and the adsorption capacity of glucose, cholesterol, and nitrite ions all increased by more than 20%. Moreover, the total phenolic content increased by 20.96%, which correlated with the higher antioxidant activity of SDF. Overall, the fermentation of corn cobs by Aspergillus niger improved the yield and functional properties of its DF.