Influence of parboiling conditions on rice grain quality characters and insect infestation with rice weevil (Sitophilus oryzae. L) of some rice cultivars

Parboiling improves rice grain hardness and reduces susceptibility to Sitophilus oryzae infestation by gelatinizing the starch and enhancing resistance.A newly designed electric machine was used to parboil four Egyptian rice cultivars-Sakha 108, Giza 178, Super 300, and Egyptian Yasmin-at 70, 75, and 80 °C and determine their susceptibility to Sitophilus oryzae L. (Coleoptera: Curculionidae) infestation. Results indicated that heating affected most traits in all four rice cultivars during both study seasons 2021 and 2022. Super 300 rice cultivar exhibited the highest hulling values (81.23 and 81.42%) when heated to 80 °C, while the Yasmin rice cultivar showed the lowest values for hulling (77.66 and 77.45%) at 70 °C. while Giza 178 cultivar showed a significant decrease in broken percentage (90.85 and 94.02%) compared to control when heated to 80 °C. The results also indicated that the Yasmin rice cultivar had the highest values for white belly, hardness, and gel consistency at 80 °C, while the Sakha 108 cultivar showed the lowest values for these traits at 70 °C. Furthermore, the protein, elongation, and water uptake characters significantly responded to the different investigated treatments. Yasmin cultivar at 80 °C showed the highest significant values for protein (9.26 and 9.47%), elongation (65.02 and 65.44%), and water uptake (453.2 and 455.1 ml water/100 g milled grains) in both seasons. Sakha 108 cultivar had the lowest values for these traits at 70 °C. The S. oryzae insects responded differently to the rice cultivars. Using Dobie's Index of Susceptibility, all cultivars were classified as resistant to S. oryzae infestation. Super 300 was moderately resistant before parboiling but resistant after heat treatment. In conclusion, the study underscores the influence of pre-storage parboiling on rice weevil infestation, suggesting that heat treatment could serve as an effective control measure. These findings emphasize the importance of parboiling conditions in enhancing rice grain quality and bolstering resistance to insect infestation.