APPLICATION OF RADIOFREQUENCY POWER FOR NON-CHEMICAL DISINFESTATION OF ROUGH RICE WITH FULL RETENTION OF QUALITY ATTRIBUTES

The presence of insect pests in stored grains constitutes an undesirable condition leading to product losses, lesser quality, and reduced market value. Currently, to protect grains, the rice industry relies on insecticides and fumigants but many of these products are facing elimination (deregistration) due to health and environmental concerns. An alternative non-chemical disinfestation process is therefore needed. Radiofrequency (RF) power was selected as it can be applied to induce well-controlled, lethal thermal energy levels, rapidly, efficiently, and throughout the whole mass of grains with minimal physical and chemical changes. Natural and laboratory infested dried storage rough rice containing all life cycles of lesser grain borers (Rhyzopertha dominica) and Angoumois grain moths (Sitotroga cerealella) were used to evaluate the efficacy of RF power treatment. This study developed relationships between temperature and disinfestation effects that were used to optimize the process's disinfestation efficiency while operating at power and thermal load levels well tolerated by the commodity. Low-thermal load RF processing at 55°C to 60°C bulk rice temperatures for short times (5 min) resulted in >99% control of all biological stages of Sitotroga cerealella (grain moth). When higher thermal loads were applied using 50°C for Sitotroga cerealella with a 2-h tempering or 60°C for Rhyzopertha dominica with 1-h tempering, the treatment provided 100% control as indicated by the absence of emerging adults over a 120-d observation period. Under these processing conditions, no moisture losses or changes in milling quality were observed. An analysis of the potential of RF power for commercial disinfestation of grains is also included.