Drying characteristics and milling quality of Parboiled rice on Drying and Tempering conditions

Drying and tempering, a known process overtime is still been done improperly which results to huge loses in both quantitative and qualitative parameters of rice. This process has been reported to contribute in hardness of grains and moisture content equalization. To test the impact of drying and tempering, this study treated Japonica rice using reported optimal parboiling conditions. The impact of different tempering conditions (0, 60 and 120 mins for 25oC, 35oC, 45oC and 55oC) at different drying temperatures (25oC, 35oC, 45oC and 55oC) including optimal drying temperature (35oC) for Japonica rice using quality indicators of milling yield, Amylose content, Protein content and whiteness. Duncan multiple test and ANOVA in SAS program were used to analyze data. Results showed a significant improvement in milling yield, the major quality parameter from 68.71% to 73.4% in the optimal condition and slight improvement in Amylose and Protein content. The parboil treatment had impact on the color of the rice. Duncan multiple test showed that tempering temperature and time for the different tempering conditions had significant impact on amylose and protein content and no significant impact on milling yield and whiteness. Oneway ANOVA test indicated tempering temperature was the most important factor in tempering rice. Results from this study will help improve the drying and tempering methods of rice and prevent huge loses that is currently recorded due to the improper and irregular way this process is currently done.