Nature of Stem Bromelain Treatments on the Aggregation and Gelation of Soybean Proteins

Abstract

Aggregation and gelation of heated soybean proteins treated with stem bromelain were investigated by determination of sulfhydryl and hydrophobicity, by polyacrylamide gel electrophoresis and by scanning electron microscopy. The heat‐induced, water‐soluble soybean protein aggregates were initially unfolded by treatment with stem bromelain and released 7S and 4S proteins. The 2S protein was completely decomposed. The enzyme attacked the basic subunits of 11S globulin and converted them to low molecular weight fragments. Aggregation and gelation developed with icnrease of fragments. Noncovalent forces, possibly through hydrophobic interaction, played an important role in the aggregation process. Scanning electron microscopy revealed a fine network structure which suggested the combination of low molecular weight fragments.