Research On Processing Of Soybean Peptides-rich Enzyme-ripening Sufu And Product Properties

Sufu is a kind of Chinese traditional fermented soybean food rich in nutrients. During sufu processing, protein were degraded into peptides and amino acids mainly depending on protease. Owing to this, sufu tasted creamy and fresh. This study examined peptides of enzyme-ripening sufu and its optimization enrichment technology. The changes of main physical chemical indicators and oxidation resistance were determined during enzyme-ripening sufu processing, as well as the quality evaluation of enzymatic sufu in order to discuss the feasibility of producing functional sufu.The paper compared different ways to extract soybean peptides from sufu with different solvents and methanol solvent was determined the best. Through single-factor experiment and response surface optimization method, the optimal extraction conditions of soybean peptides from sufu were determined as follows:solvent/sufu ratio was 9:1, extraction temperature was 58℃, methanol concentration was 70%, and extraction time was 29 min. Under the conditions, the content of soybean peptides was 60.08 mg/g. The above result offered a basis for further determining the yield of soybean peptides.Through research on processing of soybean peptides-rich enzyme-ripening sufu and product properties, the optimum conditions was determined:hydrolysis temperature was 50℃, total amount of enzyme concentration was 0.010%, ratio of enzymes Ⅰ:Ⅱ (ACCELERZYME NP50000:ACCELERZYME CPG) was 3:7, substrate concentration of soy milk was 6.0%, enzymatic hydrolysis time was 5 h. Under these conditions, hydrolysis degree of soybean protein was 25.56% and content of peptides was 106.40 mg/g.Through the study on physical chemical indicators during enzyme-ripening sufu processing, it was determined that the moisture content decreased gradually; pH values and soybean peptide content increased firstly and then decreased.7S and 11S of globulin subunits were hydrolyzed and electrophoresis strip was narrowed seen by SDS-PAGE. This mainly own to a large number of small molecular weight substances of which molecular weight was below 14.4 kDa. Amino acid nitrogen content gradually increased. The free fatty acid content increased during processing, while the fat content gradually decreased, but the change was not significant. The change of sufu structure during processing was investigated by scanning electron microscope. Large glue granular protein aggregates were degraded into small aggregates, finally disappeared. The sufu formed smooth and uniform morphology. The oxidation resistance was gradually increased during enzyme-ripening sufu processing.By studying the flavor components, textural, physico-chemical and sensory evaluation of enzyme-ripening sufu after optimization, the result was determined. The characteristic components were identified, esters 47.33%, alcohols 23.23%, ketones 14.60%, aldehydes 6.36%, and others components 8.49%. The hardness, adhesiveness of enzyme-ripened sufu fermented after 30 days were stronger than traditional sufu, but springiness, cohesiveness, chewiness of enzymatic sufu were less than traditional sufu; physic-chemical indicators and sensory of enzymatic sufu were close to the traditional sufu. The above experimental researches offered a theoretical basis for development of production process and quality indicators of functional sufu, and promoted the development of sufu industry.