Study On Co-production Of Phytic Acid And Protein Hydrolysates From Defatted Rice Bran

The utilizition of defatted rice bran(DRB) were studied in this paper. Phytic acid and RBPH were extracted from DRB. Also, the purification of phytic acid and RBPH with some properties were studied.First, phytic acid was extracted from DRB under the the optimum extraction conditions: pH 3.9, the proportion of water 9︰1, time 4.4 h and temperature 50℃, which were obtained through response surface methodology (RSM). The results showed the phytic acid extraction ratio was 85.83%, but the protein loss ratio was 10.67%.Phytic acid was separated with alkali precipitation and D318 alkalescence anion exchange resin (AAER). Sodium hydroxide(Ca(OH)2) and hartshorn solutions were chosen to precipitated phytic acid step by step at pH 9.0. The conditions of adsorption/desorption from D318 AAER were: 10mg/mL phytic acid solution at pH 2.5 with a flow rate of 1.0 mL/min for adsorption; and 1.5 mol/L NaOH elution with a flow rate of 1.0 mL/min for desorption, under which the phytic acid recovery was 96%. Finally, the obtained ratio and the purity of phytic acid were 79.20% and 94.72%.Alcalase and Protamex hydrolysing step by step were used to prepare RBPH. The optimum conditions were determined by RSM as follows: Alcalase operant conditions: pH9.0, temperature 60℃, enzyme addition 4000 NPU/g and time 1.8 h; Protamex operant conditions: pH7.5, temperature 45℃, enzyme addition 3200 NPU/g and time 2 h. Under the optimum conditions, the extraction ratio, purity and degree of hydrolysis of RBPH were 79.12%, 34.51%, and 23.34%, respectively.RBPH solution was ultrafiltrated with a membrane of molecular weight cut-off of 50 kDa to remove the impurity. Macroporous adsorption resin(MAR) of DA201-C was used for the desalting of RBPH. The conditions of adsorption/desorption from MAR DA201-C were RBPH solution at pH4.5 with a flow rate of 0.5 mL/min for adsorption, and desorption solvent flow rate was 1.0 mL/min. RBPH fractions with different amino acid compositions and hydrophobic values were obtained by gradient ethanol elution, which were RBPH-25, RBPH-50, RBPH-75 and RBPH-100. The RBPH recovery was 96.43%. Moreover, RBPH was much refined from 34.51% to 60%~78%. At last, the obtained ratio of RBPH was 66.42%.Experiments indicated that compared to SPI, RBPH had better emulsifying stability and similar emulsifying activity. The antioxidant activity of RBPH-75 was the highest. RBPH had obvious DPPH scavenging activity, antioxidant activity in linoleic acid system and reducing power but the ferrous ion-chelating activity was much lower than EDTA. Also, it was found that RBPH exhibited some cholesterol-lowering activity. RBPH-50 and RBPH-75 had higher cholesterol-lowering activity.