Optimization of Variable Temperature-Tempering Drying Process and Study on Proteins Structure of Indica Japonica Hybrid Rice

Abstract

In order to improve the drying quality of rice, Indica and japonica hybrid rice were taken as the object and evaluated by waist burst rate, head rice rate, energy consumption and drying time in this experiment. Single factor and response surface analysis were combined to optimize the drying process. The effects of variable temperature-tempering drying on proteins structure and thermal properties of indica and japonica hybrid rice were investigated by differential scanning calorimetry. Fourier infrared spectroscopy and fluorescence spectroscopy. The results showed variable temperature-tempering drying (temperature range 30~60 ℃) that under the conditions of temperature rise 5 ℃, wind speed 1 m/s and tempering ratio 0.6, the rice could be kept in the glassy state, and the waistband burst rate and head rice rate after drying were 79.89% lower and 39.54% higher than those in the constant temperature group (60 ℃), respectively. Under these conditions, the polarity of rice proteins decreased and intermolecular aggregation occured, which improved the thermal stability of rice proteins, and the α-helix content increased from 16.21% to 17.64%. Scanning electron microscope results showed that the surface structure of protein was not significantly affected by variable temperature-tempering drying. The experiment explored and verified the drying mechanism of hybrid rice with variable temperature-tempering drying, which would provide a theoretical and practical reference for the research of high quality drying of hybrid rice.

Keywords

• rice
• variable temperature drying
• tempering
• glass transition
• protein structure
• thermal characteristics