30C-9 |
Protein extraction from heat-stabilized defatted rice bran: IV. Optimization of enzyme conditions with response surface methodology |
S. Tang and N. S. HETTIARACHCHY. Department of Food Science, University of Arkansas, Fayetteville, AR 72704 Enzyme concentration, water to bran ratio, incubation time, pH, and temperature are factors that influence an enzyme to optimize maximum protein extraction from heat-stabilized defatted rice bran (HDRB). To optimize these factors, full or fractional factorial design may not achieve this goal because of the large number of experiments. Response surface methodology (RSM), with Box-Draper saturated design (BDSD) or Second order rotatable design (SORD), can be used to reduce experiment numbers and predict desirable extractability and its corresponding conditions. The objectives of this research were to optimize the enzyme conditions for protein extraction from HDRB by using RSM, and to determine the factor contribution. Ranges of 0-110000 units amylase /10g rice bran, 35-55 oC, water to bran ratio of 5-20:1, and 1-8 h of incubation time were used with BDSD for optimization of amylase. Pectinase of 0-3500 units/10g rice bran, pH 1.5-6.5, water to bran ratio of 5:1-20:1, time of 1-8 h, and 30-60 oC were selected to optimize the conditions with SORD. The extracted proteins were determined by Kjeldahl method. Data were analyzed by RSM. Protein extractability increased with the increase of temperature, water to bran ratio, amylase, or time. R2 for the fit model was 0.99. Factor contribution to extractability was enzyme > temperature > time > ratio. Among the treatments, the highest extractability was 58.4% and the lowest was 9.5%. For pectinase, maximal extractability was obtained after fitting with a second order linear model at pH3.6, 4.5 h of incubation time, water to bran ratio 20:1, pectinase 3500 units/10g rice bran, and 60 oC (R2=0.87). Factor contribution was enzyme concentration > pH > temperature > ratio > time. Extractabilities under different enzyme conditions were predicted and confirmed with real experimental values. RSM is an appropriate tool for optimization of multiple factors in protein extraction.
Session 30C, Food Chemistry: Proteins
|