Abstract:Soy sauce residues (SSR) were the main by-products of soy sauce fermentation, which contained a large amount of valuable components but failed to be reused reasonablely. Recycling the dietary fiber (DF) from SSR could make good use of the waste and remedy the issue of environmental hazards. The SSR insoluble dietary fiber (IDF) was prepared by a novel method of low temperature continuous phase transition extraction. Based on previous single factor experiments, the process parameters were optimized through the response surface methodology (RSM) for maximum IDF yield. Washing and enzymolysis were accompanied for purification. The functional characteristics of SSR IDF were investigated. In combination with the scanning electron microscopy (SEM), mechanism of the relationship between its microstructure and functional characteristics was explained preliminarily. Results showed that the best extraction conditions were 50 mesh raw material ,extraction regent n-butane solvent, extraction pressure 0.5 MPa, extraction temperature, 45 ℃ and extraction time 67 min, under which the oil content of obtained IDF was less than 1%. After purification, the purity could reach as high as 70.9±0.28%. Functional tests showed that SSR IDF had good features, and water holding capacity, expansibility and oil binging ability were 6.65±0.07 g/g, 5.83±0.11 mL/g and 2.23±0.03 g/g, respectively. Compared with commercially available soybean IDF products, the oil binging ability of SSR IDF was paticulary significant. From the SEM figures, the good functional characteristics of SSR IDF were related to its loose structure formed by the cellulose.
