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 problem with long preparation time and hard texture. Parboiling is hydrothermal process that change rice starch from crystalline to amorphous. The parboiling process of rice consist 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 autoclave (5, 10 and 15 min) and 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 autoclave, and 3.8 freeze - thaw cycles. This optimum condition resulted in parboiled black rice with 25.84 min cooking time, 4.93 total color difference 101.80 N hardness of cooked rice, 49.04 N chewiness of cooked rice, 5.32 kg rice grain hardness.