Enzymatic Optimization of Riceberry Bran Protein Hydrolysate Extraction and Characterization

Defatted riceberry bran (DRBB) by screw press contains high nutrition including protein and
phytochemicals. This research is aimed to optimize the protease enzymatic extracting condition
for riceberry bran protein hydrolysate (RBBPH) and characterize protein hydrolysate
compositions. The experimentation was conducted using central composite design (CCD). The
Response surface methodology (RSM) was used to determine the optimum condition in order to
obtain maximum protein yield, total phenolic content (TPC) and anthocyanin. The three
independent variables including enzyme to substrate ratio (E/S; 0.1-2%), temperature (T; 30-
70°C), and hydrolysis time (t; 30–360 min) were studies while the ratio of rice bran to water by
weight and pH were fixed constant at 1:5 and 8.0, respectively. The results showed that the model
of protein yield and anthocyanin content were significant (p< 0.05). The coefficients of
determination (R2) of protein yield, TPC and anthocyanin were 0.87, 0.55 and 0.80, respectively.
The optimal condition was 0.82% enzyme/substrate at temperature of 43.75ºC for 140.38 min.
Under this condition, the values for protein yield, TPC and anthocyanin content were 14.98 g,
226.84 mg GAE and 3.25 mg Cyn-3-Glu per 80g DRBB, respectively with degree of hydrolysis
(%DH) 21.26%. The RBBPH after freeze-dried contained 21.62% of total protein, 33.85 mg
GAE/g of TPC and 0.47 mg Cyn-3Glu/g of anthocyanin content. The extract exhibited high
antioxidant activities (DPPH; IC50 = 0.052 mg/mL and FRAP; IC50 = 2.27 mg/mL). The RBBPH
was high in glutamic acid and molecular weight was between 5-50 kDa.

Keywords: proteinhydrolysate, riceberry bran, enzymatic extraction, anthocyanin, antioxidant

*Corresponding author: Tel.: 02-5620339, 02-9428600-3 to705 Fax: 02-5620338
 E-mail: aapsrt@ku.ac.th