Effect on the Structure, Physicochemical Properties and Functional Properties of Insoluble Dietary Fiber from Soybean Residue by Modification Methods

To investigate the effects of different modification methods on the structure, physicochemical and functional properties of soybean residue insoluble dietary fiber (SIDF), high-speed shear, compound enzymatic digestion and the combination of the two methods were used to modify SIDF. The structural, physicochemical and functional properties of SIDF were characterized by particle size, Fourier transform infrared (FTIR) spectroscopy, water holding capacity (WHC), oil holding capacity (OHC), swelling capacity (SC) and cation exchange capacity. Results showed that the particle size of modified SIDF was significantly reduced (P<0.05), and the WHC, OHC, and SC were significantly increased (P<0.05), in which the composite modified SIDF had the smallest particle size and the strongest WHC (6.74±0.11 g/g), OHC (4.22±0.09 g/g), and SC (7.55±0.06 mL/g). Spectral analysis showed that degradation of cellulose, hemicellulose and lignin occurred after the modification treatment and destruction of the crystalline zone, among which cellulose and other substances degraded the most in the composite modification-treated samples, and the destruction of the crystalline zone was the most obvious. Scanning electron microscopy (SEM) results showed that honeycomb pore structure appeared on the surface of the samples, with the composite-modified samples having the densest and most numerous pores. The modified SIDF had excellent cation exchange capacity, nitrite adsorption capacity, etc., of which the compound modified functional properties were optimal. In summary, high-speed shear combined with enzymatic modification treatment can effectively improve the physicochemical and functional properties of SIDF, providing a theoretical basis for its comprehensive utilization.