Application of pulsed electric field and drying temperature response on the thermodynamic and thermal properties of red rice starch (Oryza Sativa L.)

The study evaluates the application of pulsed electric field (PEF) and investigates the effects of drying temperature on the thermodynamic and thermal properties of red rice starch (Oryza Sativa L.). The grains underwent extraction process using 0.5% of sodium metabisulfite; the pastes were pretreated with application of PEF (10 and 30 kV/cm); and the pulse frequency was 600 Hz, 6 mu s wide, and 90-s residence time. The pretreated pastes were subjected to temperatures of 40, 50, and 60 degrees C with an air velocity of 1.0 m/s. Evaluation of the thermodynamic properties and thermal properties of the PEF-pretreated starch was carried out after adjusting the diffusive models using boundary conditions of the first and third types. PEF showed maximum reduction in the time process of 180 min (46.15%) for the PEF 30 kV/cm at a temperature of 60 degrees C. The boundary condition of the third type showed a coefficient of determination (r(2)) greater than .98 and low values of the chi 2 function with diffusivity ranging from 2.159 to 7.877 x 10(-5) m(2)/min. A decrease in activation energy (44.59 kJ/mol) was observed revealing positive and decreasing values. The different intensities of PEF resulted in greater moisture transport presenting a uniform distribution within the starch throughout the drying process. The temperature and gelatinization enthalpy were also influenced by PEF. Therefore, PEF can reduce the costs of the drying and gelatinization process reducing environmental impacts generated by high energy consumption. Practical Applications The results obtained will contribute to the optimization of industrial production and will serve as a basis for the implementation of a pretreatment of FPE for large-scale application. This method is promising because it modifies the cellular structure of biological cells such as red rice starch and increases the convective drying rate, reducing drying time and energy expenditure in the process.