Combined effects of drying methods and limited enzymatic hydrolysis on the physicochemical and antioxidant properties of rice protein hydrolysates

The combined effects of drying methods and limited enzymatic hydrolysis on the techno-functional characteristics of rice protein hydrolysates(RH)were investigated.With the increasing hydrolysis degree,the average size,exposed and total SH content,iron chelating capacity,hydroxyl and DPPH radical scavenging activity increased.Drying methods and enzyme type can alter the conformation of protein.Trypsin-derived spray dried RH exhibited higherα-helix contents while neutrase-derived ones had lowerα-helix contents.The freeze-dried RH owed higher hydroxyl and DPPH scavenging activity than their spray-dried counterparts,which was related to higher sulfhydryl group and hydrophobic amino acids contents.RH derived from trypsin had higher metal chelating capacity than that from neutrase,which was in an agreement with higher amount of peptide<1000 Da.The shifting to lower relaxation time in spray-dried RH reflects lower water absorption capacity and slower water mobility,which are less susceptible to spoilage bacteria.Freeze drying would be a more prevalent technique for fully utilization of RH as bioactive components in the food system.