Physical and flow properties of rice protein powders

• Physical and flow properties of rice protein powders were investigated.
• Microstructure was influenced by substrate, processing and drying techniques used.
• Protein hydrolysates were more hygroscopic compared to their intact counterparts.
• The rice protein-enriched ingredients analysed displayed good flowability.

In this study, the physical and flow properties of a range of rice protein powders, including three rice protein concentrates (RPC 1, RPC 2 and RPC 3), two rice endosperm protein hydrolysates (RPH 1 and RPH 2) and two rice bran protein hydrolysates (RBPH 1 and RBPH 2) were determined and compared with those of selected dairy protein powders, i.e., skim milk powder, whey protein isolate and whey protein hydrolysate. The physical properties analysed included particle size distribution, particle shape and surface characteristics. Differential scanning calorimetry analysis demonstrated that RBPH samples had lower thermal stability compared to RPC and RPH samples. Analysis of the moisture sorption properties showed a higher hygroscopicity at high relative humidity values of hydrolysed protein powders compared to their intact counterparts. All protein ingredients analysed displayed good flowability (i.e., easy-flowing or free-flowing behaviour), while the bulk density of intact rice protein ingredients was higher than that of their hydrolysed counterparts. The results obtained in this study enable enhanced control of the behaviour of rice protein powders during storage, handling and processing.