Emulsifying properties of defatted rice bran concentrates enriched in fiber and proteins

Abstract

Abstract: BACKGROUND: Rice bran (RB), a by-product of rice milling industry, constitutes around 10% of the total weight of rough rice. The interest in the use of RB is centered on its nutritional quality, its low cost and its worldwide extensive production. As RB is commonly used for oil extraction, the defatted rice bran (DRB) is obtained as a second by-product. The aim of this work was to obtain a defatted rice bran concentrate (DRBC), enriched in protein and fiber, from defatted rice bran flour (DRBF) and to determine its physicochemical and emulsifying properties. RESULTS: To obtain the DRBC, the starch was efficiently hydrolyzed (> 98%) with α- amylase and amyloglucosidase, with the concomitant increase of crude protein (from 154.7 to 274.3 g kg-1) and total dietary fiber (from 276.1 to 492.3 g kg-1) proportions. DRBC exhibited a loss of protein solubility and increased surface hydrophobicity compared with DRBF. DRBC dispersions with and without previous ultrasound treatment were prepared. The sonication led to an increase in the apparent viscosity. Emulsions were prepared with dispersions with and without previous ultrasound treatment and showed high stability in quiescent conditions during 28 days. However, the emulsions prepared with dispersions treated with ultrasound resulted in lower D4,3 values and higher elastic and viscous moduli. CONCLUSION: The rice bran concentrate can be used to obtain stable O/W emulsions, including both fractions, soluble and insoluble, in acidic and neutral conditions. Thus, these innovative findings contribute to increase the added value of this important by-product of ricemilling industry.