Ohmic heating using electrolytes for paddy parboiling: A study on thermal profile, electrical conductivity, milling quality, and nutritional attributes

Abstract

AbstractOhmic heating (OH), a novel thermal technique could be utilized for paddy parboiling to improve milled rice quality. In this research, two paddy varieties (one traditional and one modern variety) were subjected to OH at different salt concentrations (0%, 0.3%, 0.5%, 0.7%, and 0.9%) and voltage gradients (10, 12, 14, 16, and 18 V/cm) and their influence on thermal profile, electrical conductivity (EC), milled rice quality, and nutritional profile were studied in comparison to the conventional steaming method. A factorial design was used to determine the effect of variety, voltage gradient and holding time on head rice yield (HRY), hardness and color difference of parboiled milled rice. Results indicated the significance of salt and voltage on processing time and HRY. On increasing, both enhanced the EC and heating rate leading to a great reduction in parboiling duration whereas HRY increased on lowering the voltage. High significant effects were observed between the factors for HRY and color. The maximum HRY and hardness were obtained for OH at 0.7% salt and 12 V/cm. This treatment when compared to steaming, consumed less energy, and provided less chalkiness, better HRY and hardness for both varieties to a greater extent. OH also positively impacted the nutritional profile of parboiled rice as it retained more protein and fat than the conventional method. These results reveal the superiority of OH in providing a significant favorable impact on the parboiled milled rice quality and has a great potential to be used for paddy parboiling.Practical applicationsOhmic heating is an emerging thermal technique having the potential for rapid uniform heating. In this study, OH was utilized for paddy parboiling by incorporating electrolytes for replacing the conventional steaming method. Steaming requires a boiler for generating steam, which adds to the processing cost and equipping OH eliminates the need for a boiler. This will save water, energy, space, manpower, and maintenance requirements. OH also reduces the parboiling duration, while improving parboiled rice quality. The ohmic behavior of paddy will also facilitate the design of continuous ohmic systems for paddy parboiling which can be immensely useful in the rice processing industry.