A Novel Fermented Food Product Prepared from Soybean Protein-Calcium-Gel with Monascus Fungus: Changes in Protein and Nitrogen Compounds during Fermentation

Abstract

The aim of the present study was to investigate the changes in protein and nitrogen compounds in a novel fermented product generated from soybean protein-calcium-gel (SP-Cal-Gel) and Monascus fungus during fermentation. Slab SDS-polyacrylamide gel electrophoresis and measurement of nitrogen contents clearly revealed the occurrence of protein digestion in the form of degradation of α'-, α-, and β-subunits in β-conglycinin and of acidic polypeptide in glycinin; however, the band of basic polypeptide in glycinin still remained. The ratios of water-soluble nitrogen and TCA-soluble nitrogen to total nitrogen reached 52.4 or 46.6% after 60-days ripening, respectively. Moreover, involvement of a large amount of free amino acids, especially aspartic and glutamic acids, were shown in this novel fermented SP-Cal-Gel food product.