Optimization of Process Paramaters of Parboiled Black Rice Using Response Surface Methodology

Abstract

Black rice is well known as healthy food. Nowadays, some people try to change their diet with this rice. However, it still has a problem with long preparation time and hard texture. Parboiling is a hydrothermal process that changes rice starch from crystalline to amorphous. The parboiling process of rice consists of soaking in sodium citrate solution, high-pressure cooking, freezing-thawing and drying. The aim of this research was to find the optimum condition from three processing variables: concentration of sodium citrate (0, 2, 5 and 5%, w/v), cooking period in an autoclave (5, 10 and 15 min) and a number of freeze-thaw cycles (1, 2.5 and 4). The optimum condition was achieved with 3.8% sodium citrate concentration, 5 min cooking in an autoclave, and 3.8 freeze-thaw cycles. This optimum condition resulted in parboiled black rice with 25.84 min cooking time, 4.93 total colour difference 101.80 N hardness of cooked rice, 49.04 N chewiness of cooked rice, 5.32 kg rice grain hardness.