Effect of moisture content on physical properties of Japonica cultivar paddy and whitened rice

The objective of this study was to investigate some physical properties of Japonica cultivar which is widely cultivated in Mazandaran، Iran in two types (paddy and whitened). Some physical properties were evaluated as a function of moisture content for paddy and whitened rice in the range of 10-18% w. b. Results show that physical properties of both rice types are influenced by moisture content. Data obtained for physical properties of paddy and whitened rice are respectively as follows: thousand seed weight 6. 69-7. 11 g and 4. 56-5. 02 g، length 3. 33-3. 49 mm and 2. 72-2. 95 mm، width 2. 15-2. 36 mm and 1. 85-2. 08 mm، thickness 4. 05-4. 32 mm and 3. 04-3. 35 mm، arithmetic mean diameter 4. 054. 32 and 3. 04-3. 35، geometric mean diameter 3. 62-3. 87 and 2. 83-3. 13، sphericity 54. 11%-54. 43% and 62. 60%-62. 35%، grain volume 5. 85-6. 68 mm3 and 3. 54-4. 30 mm3، surface area 35. 11-40. 10 mm2 and 21. 25-25. 81 mm2، true density 1103. 05-1203. 17 kg. m-3 and 1360. 44-1444. 05 kg. m-3، porosity 44%-51% and 34%-41%، angle of repose 22. 61-2768 angle and 16. 15-20. 29 angle، and static coefficient of friction 3. 96-4. 66. and 2. 98-5. 09 increased by increase in moisture content. Bulk density reduced from 614. 33 and 885. 00 kg. m-3 to 588. 33 and 850. 66 kg. m-3 respectively for paddy and whitened rice. All parameters increased by moisture increase except for bulk density showing decreasing trend. In all cases، data related to paddy rice (having bran) were more than whitened one except for bulk density. Altogether، a significant difference was observed between obtained results.