Effect of Demulsification Methods on the Quality of Oil Recovered from the Emulsion Formed during Enzymatic-assisted Aqueous Extraction Process of Soybean Oil and the Flavor of Hydrolyzed Protein

In order to study the effect of demulsification methods on the quality of oil from cream produced by crude enzymatic-assisted aqueous extraction process of soybean oil and the flavor of hydrolyzed protein,the physicochemical properties and fatty acid composition of recovered oil by isoelectric point,CaCl₂ addition,Alcalase enzyme method and heating demulsification method were analyzed respectively,while the solvent extraction oil was as the control. The results showed that the color,acid value,peroxide value,saponification value and iodine value of the oil obtained by different demulsification methods were lower than those of solvent extraction oil. In all demulsifying oil,the acid value of oil acquired by isoelectric point demulsification method was the highest(0.83 mg/g),followed oil from heating demulsification,the acid value of CaCl₂ addition and Alcalase enzymatic demulsification was the lowest(0.52 mg/g). The peroxide value of oil from heating demulsification method was higher than those of other demulsification methods,reaching 0.85 μg/g,the peroxide value of oil from CaCl₂ addition and Alcalase demulsification methods was the lowest(0.62 μg/g). There was no significant difference in color,saponification value and iodine value among demulsifying oils(P>0.05). The fatty acid composition of demulsifying oil was the same as that of solvent extraction oil,and the total contents of unsaturated fatty acid was above 84%,which met the standard of edible oil recommended by the International Codex Commission. Therefore,the quality of demulsified oil was better than solvent extraction oil,and the quality of CaCl₂ and Alcalase demulsifying oil was the best. The essential amino acid contents of crude enzymatic hydrolyzed protein was close to that of raw soybean protein. Although crude enzymatic hydrolyzed protein still had a bitter taste,the bitterness value was lower than that of Alcalase enzymatic hydrolyzed protein,which showed crude enzymatic hydrolyzed protein still maintained the nutritional quality of soybean protein.