Uso da irradiação micro-ondas para melhorar a qualidade do arroz parboilizado

Abstract

Some of the main drawbacks of the rice parboiling process are the intensities of grain color and flavor, which may be due to the browning reactions during the hydrothermal stage and the vaporization stage, these characteristics adversely affect consumer acceptability. The processes of parboiling have evolved, due to the expansion in the research on rice parboiling and the development of new techniques. However, there are limitations throughout the process, demonstrating the importance of searching for new techniques that can reduce the process time and the browning of parboiled rice grains. The development of faster and more efficient rice parboiling processes, such as microwave irradiation, can improve grain quality and reduce browning reactions. This study evaluated the effects of microwave irradiation on the parboiling process on morphological, technological and structural properties of rice grains. Parboiling was performed via microwave irradiation under the same temperature conditions (soaking and vaporization) used in the conventional process. However, two heating stages (400 and / or 500 W) were used at different exposure times to microwave irradiation (a) stage first: 10, 20, 30 and 40 min and (b) stage second: 0,5 and 10 min. The rice grains submitted to the first step of microwave irradiation absorbed more water and lost less leached solids when compared to the parboiled by conventional parboiled rice. Microwave irradiation decreased the cooking time of rice grains and modified their protein solubility when compared to conventional parboiling. In addition, this technique modified the morphology and crystalline structure of the grains. The use of microwave heating in the parboiling process significantly reduces processing time, making it possible to obtain parboiled rice grains with greater whiteness.