Studies On Processing Of Soybean Isoflavone-Rich Enzyme-Ripened Sufu And Product Properties

The paper determined the extraction method of soybean isoflavone, analyzed the total amounts of soybean isoflavone during the manufacturing process of enzyme-ripened sufu and optimized the sufu process for reducing the loss of soybean isoflavone to discuss the feasibility of producing functional sufu.It was determined that ethanol solution was used as extraction solvent and solid-to-liquid ratio was 1.5:10. The optimum conditions for extraction of soybean isoflavone were determined using response surface methodology by Box-Behnken design. The optimized conditions were as follows:extraction temperature was 65℃, extraction time was 2.5h and ethanol concentration was 65%. Total amounts of soybean isoflavone during the manufacturing process of enzyme-ripened sufu were analyzed. The result showed tofu production process was one of the most important reasons, which led to loss of soybean isoflavone.The paper studied the effects of accession amount of edible gum, inoculating concentration of LL-50A and accession amount of proteinase preparation on soybean isoflavone. The tofu yield and soybean isoflavone yield were adopted as indexes, L9 (33) orthogonal test was carried out. At last, we ranked the influence in turn:accession amount of carrageenan> accession amount of proteinase preparation>inoculating concentration of LL-50A. The optimized technology condition:accession amount of carrageenan was 1.25%o, inoculating concentration of LL-50A was 0.03% and accession amount of proteinase preparation was 10μL/100mL. Under this condition, tofu yield was 213.43 g/100g and soybean isoflavone yield was 2.52 mg/g.After optimization had been taken, sensory evaluation result of enzyme-ripened sufu fermented after 30 days was similar to sufu fermented after 6 months in traditional process. Hydrolysis degree of soybean protein and total acid gradually increased in the manufacturing process of enzyme-ripened sufu. Fat content decreased and hardness first increased, then decreased. DPPH radical scavenging activity, hydroxyl radical scavenging activity and reducing capacity were determined to evaluate the antioxidant activity, which increased in the whole process. Hydrolysis degree of soybean protein of enzyme-ripened sufu fermented after 30 days was 34.39%, total acid content was 3.50 g/100g, fat content was 20.36 g/100g and cone penetration was 234.7×10-1mm. Protein-grain colloid complex of enzyme-ripened sufu fermented after 30 days disappeared under scanning electron microscopy, which made the internal structure of sufu uniform.In enzyme-ripened sufu fermented after 30 days, it was showed that soybean protein was degraded into low molecular weight protein and soybean peptide, whose molecular weight was below 20.1 KD through gel electrophoresis analysis. The headspace volatile compounds in enzyme-ripened sufu fermented after 30 days included 56 volatile compounds. The characteristic components were identified, had 64.84% esters,4.97% alcohols,8.50% aldehydes,0.21% acids and 1.89% ketones. The enzyme-ripened sufu fermented after 30 days and commercial sufu fermented after 6 months in traditional process both had 33 identical volatile compounds. The variety and percentage of volatile compounds of enzyme-ripened sufu were close to commercial sufu. The above experimental researches offered a theoretical basis for development of functional sufu.