| In order to investigate the status of protein hydrolysis and oil release during crude enzyme-assisted aqueous extraction of soybean oil, the extraction rates of total oil and total protein were monitored, and relative molecular weight of the protein was detected by gel chromatography. Meanwhile, scanning electron microscopy (SEM), light microscopy with Coomassie brilliant blue and Sudan red Ⅲ staining were used to reveal the distribution of oil and protein in soybean powder, hydrolysate and emulsion during the enzymolysis. The results showed that with the increase of enzymolysis time, the degree of protein hydrolysis deepened, and the oil release amount increased. The content of polypeptides with relative molecular weight higher than 33 000 Da gradually decreased, while the content of short polypeptides with relative molecular weight less than 5 500 Da increased. The highest extraction rates of total oil and total protein were obtained at enzymolysis time 6 h, which were 94.2% and 90.1% respectively, the content of short peptides (<5 500 Da) in protein hydrolysate was the highest, accounting for 49.63%, and the content of polypeptides with relative molecular weight higher than 33 000 Da was only 21.15%. SEM indicated that the protein and oil in soybean powder were gradually degraded and released by enzymolysis so that the original intact cells turned into empty residues. Light microscope pictures showed that with the hydrolysis of soybean powder, the protein content in hydrolysate increased progressively, and the oil released was distributed in hydrolysate and emulsion. The number and diameter of oil droplets increased with the extension of enzymolysis time. |
