Optimization of process parameters of osmotic pressure treatment and heat moisture treatment for rice starch using response surface methodology

Abstract

In the present investigation, rice starch isolated from broken rice of Ranjit variety of Assam was modified by osmotic pressure treatment (OPT) and heat moisture treatment (HMT). Response surface methodology (RSM) based on face-centered central composite design (FCCD) was used to optimize the process conditions of OPT and HMT with independent variables namely, temperature (X1:100–120 °C) and time (X2:15–45 min); and additionally moisture content (X3:20–30%) in HMT. The aim was to obtain higher final viscosity, setback viscosity and gel hardness; lower swelling power and solubility of rice starch on modification. All the independent factors were established as significant (p < 0.05) in deriving the OPT and HMT starches. Temperature of 117 °C and time of 35 min were the optimal conditions for OPT that gave final viscosity of 4718.42cP, setback viscosity of 2312.27cP, gel hardness of 73.12 g, swelling power of 16.21 g/g and solubility of 11.45%. The FCCD resulted in final viscosity of 5341.62cP, setback viscosity of 3337.05cP, gel hardness of 75.11 g, swelling power of 10.57 g/g and solubility of 5.39% at optimum conditions, namely, temperature of 111 °C, moisture content of 29% and time of 45 min for HMT. The response surface plots showed that OPT caused increase in the responses with increasing time and temperature except swelling power. Final viscosity, setback and gel hardness tended to increase but swelling power and solubility reduced in HMT with increase in time, temperature and moisture content. These research findings open up scope for further investigation on the OPT and HMT rice starches and their effective application in rice noodle processing.