Optimisation of Parboiling Process using Response Surface Methodology (RSM) to improve the Physical Properties of Parboiled Milled Rice

Abstract

The optimisation of the parboiling conditions of a popular rice variety in Nigeria using Response Surface Methodology (RSM) was carried out. The parboiling conditions-Initial Soaking Temperature (IST), Soaking Time (ST) and Final Moisture Content (FMC) were statistically combined in a Central Composite Design (CCD) with the effects on selected physical properties of milled rice of FARO 52 rice variety determined. Results obtained were analysed to determine the optimum parboiling conditions (OPC) to produce milled rice with improved physical qualities. Results showed significant influence (at 95% confidence level) of IST, ST and FMC on the head rice yield, broken rice ratio, grain hardness and grain colour of the parboiled milled rice. The optimum paddy parboiling conditions for improved physical qualities of milled rice are: Initial soaking temperature: 67.7°C; Soaking time: 13hrs 18minutes and Final moisture content prior to milling: 12.7%. These optimal conditions are expected to produce parboiled milled rice with the following physical characteristics: Head rice yield, 70%; Broken rice ratio, 2.18%; Grain hardness, 74.7N and Grain colour, 25.8 with a composite desirability of 76.3%.