Research On Production And Functional Properties Of Soybean Peptides By State Solid Fermentation Using Soybean Meal

Characteristics of soybean peptides produced by solid state fermentation used B subtilisGA15and soybean meal was explored in this paper. Production technology of soybeanpeptides was determined by optimizing, the single stage-fermented: fermentation temperature,30℃; substrate height,1.75cm; initial moisture content,44%and fermentation time,72h.The two stage-fermented: fermentation temperature,30℃; substrate height,1.75cm; initialmoisture content,44%and fermented44h, firstly; followed by fermentation temperature,40℃; substrate height,1.75cm; moisture content,44%and fermented28h. The resultsshowed that the two stage-fermented was more suitable for the production of soybeanpeptides, content of soybean peptides could up to19.75%fermented by the twostage-fermented,6.45%higher than the single stage-fermented after fermented72h.SDS-PAGE showed that lipoxygenase of soybean meal was completely degraded boththe single stage-fermented and the two stage-fermented after fermented72h, however, α’-, α-,β-subunit of7S and the acidic subunits, the basic subunits of11S were degraded partially, α’-reduced71.95%, α-reduced58.53%, β-reduced86.55%, the acid subunits reduced59.46%and the basic subunits reduced48.18%when fermented72h by the single stage-fermented,α’-reduced89.39%, α-reduced87.31%, β-reduced100.00%, the acid subunits reduced94.86%and the basic subunits reduced70.66%when fermented72h by the twostage-fermented. Molecular weight distribution showed that the molecular weight of soybeanproteins was reduced due to degradation of microorganisms and protease. About45.92%(single stage-fermented) and56.33%(two stage-fermented) soybean proteins were changedinto soybean peptides, which molecular weight was less than10000Da after fermented72h.Amino acid analysis showed that nutritive material of soybean meal was consumed bythe metabolic activity of B subtilis GA15in the solid state fermentation. Thus resulting in thecontent of essential amino acid increased significantly, however, most of the non-essentialamino acid content is significantly reduced. The content of free amino acids increased withfermentation time, which up to34.568mg/g (single stage-fermented) or35.727mg/g (twostage-fermented) after fermented72h. Particle size distribution and electron microscopy experiments showed that degradationof microorganisms and protease on the soybean proteins were occurred on the surface ofsoybean meal particle in the solid state fermentation, and the degradation were extended to theinside of soybean meal particles with fermentation time. So that soybean meal particle sizedecreased, the particle size of soybean meal was decreased from64.76μm to28.98μm(single stage-fermented) or28.38μm (two stage-fermented) after fermented72h.Soybean peptides which had the higher purity and molecular weight less than10000Dawas obtained at30℃,10min and pH4.0, which extraction rate was87.99%. Amino acidsanalysis showed that amino acid composition of soybean peptides was similar to soy proteins.Soybean peptides solubility almost100%under acidic or neutral conditions and can promotethe growth of yeast. Furthermore, superoxide anion radical was effective scavenged bysoybean peptides, experiments showed that the inhibition rate of soybean peptides onpyrogallol autoxidation can up to101.59%(single stage-fermented) or98.56%(twostage-fermented).