Identification of Peptides in Sediments Derived from an Acidic Enzymatic Soy Protein Hydrolysate Solution

Soy peptides were produced by microbial protease digestion of soy proteins. Under an acidic condition (pH3.8) , soy peptide solution (5% w/v) yielded sediment during chilled storage. The object of the present study was to identify peptides in the sediment in order to elucidate the sedimentation mechanism. Peptides remaining in solution after chilled storage had a molecular mass of 200-5,000 Dalton (Da) , based on the elution volume obtained from size exclusion chromatography. However, peptides extracted from the sediment using 30% acetonitrile-0.1% trifluoroacetic acid had a molecular mass larger than 2,000 Da. Only limited numbers of peptides f (71-88) , f (340-362) , f (335-362) and f (310-356) of β-conglycinin α subunit were identified in the sediment. These results demonstrated that the sediment was produced from relatively large molecular peptides derived from the C-terminal region of the β-conglycinin α subunit. Moreover, the major peptide in the sediment was sensitive to cleavage by mammalian trypsin.