Effects of heat -moisture treatment on physicochemical properties and protein quantity of brown red rice

Abstract

Brown red rice (BRR) has been increasingly received great attention from consumers because of its positive contributions on both nutritional and medical areas. Heat – moisture treatment (HMT) was reported to contribute to increase the resistant starch (RS) of rice, which plays an important role in enhancing the nutritional value of BRR through the reducing the risk of obesity and diabetes. This study was carried out to investigate the changes in chemical compositions (ash content, lipid content, protein content and carbohydrate content), flour properties (flour hydration properties and pasting properties) and the quantity of main rice proteins (Albumin, Globulin, Glutelin and Prolamin) of BRR after applying HMT with different moisture content (20%, 25% and 30%) and different heating temperature (1000C and 1200C). HMT did not cause the significant changes in chemical compositions of BRR. However, significant differences in flour hydration properties (the slight decrease of water solubility index and swelling power), pasting properties (the gently increase of pasting temperature and the decrease of peak viscosity, final holding viscosity and breakdown), quantity of rice protein (the decrease of both four protein fractions) of treated samples in comparison with control one were observed in this research. In addition, differences in temperature and moisture contents among six treated samples did not create differences in almost mentioned properties, and the sample that had lowest moisture content and treated at lower temperature, the 1000C – 20% sample, was evaluated to be the most similar to the control sample. In conclusion, HMT did not give significant effects on physicochemical properties of BRR, while cause slight decrease in protein quantities, but these properties of HMT treated BRR may be acceptable. Key words: Brown red rice, Heat – moisture treatment, Chemical composition, Flour hydration properties, Pasting properties, Rice protein quantity.