Effect of stabilisation treatment of rice bran on nutritional quality of protein concentrates

Protein concentrates were prepared from unstabilised, acid stabilised, heat stabilised and parboiled rice bran, either freeze dried or roller dried. They were assessed for their nutritional quality by both in vivo and in vitro assays. The essential amino acid profile of protein concentrates was comparable to rice proteins or rice bran proteins as such. Limiting amino acids of concentrates were threonine and isoleucine. Essential amino acid indices for different samples ranged from 72.4 to 77.6. Lysine content was high (4.32-5.55 g/16 g N) of which 52-57% was available. Freeze dried protein concentrate from untreated and acid stabilised rice bran exhibited very high in vitro digestibility (84.1 and 86%, respectively) whereas protein concentrates from heat stabilised and parboiled rice bran had lower digestibility of 57.3 and 61.2%, respectively. Roller dried samples from untreated and acid stabilised rice bran showed high digestibility with pepsin and pancreatin but low value with pepsin, indicating effect of heat on pepsin digestibility. The results of animal assays can be summarised as follows. The PER values of diets based on protein concentrates from untreated and acid stabilised rice bran at 10% protein level were 2.16 and 2.34 and at 15% protein level were 2.20 and 2.11, respectively. Net protein ratio and nitrogen utilisation from both protein concentrates were also high and not significantly different from the standard protein.