Processing quality of rough rice during drying - modelling of head rice yield versus moisture gradients and kernel temperature
Résumé
The published literature reviews various factors responsible for rice breakage during milling. Artificial drying immediately after harvesting is one of the main causes of kernel fissures in temperate countries like France. These virtually invisible fissures lead to high breakage ratios during milling. The present work attempts to construct a simulation tool capable of predicting head rice yield during drying, so that the design of industrial rice dryers can be improved. Relationships were established between head rice yield and both moisture content gradient and kernel temperature. The influence of the temperature and evaporating capacity of the drying air on head rice yield after processing was studied. Experimental quality data were fitted to a kinetic model. Evaporating capacity was identified as the principal factor responsible for head rice yield reduction: head rice yield is not affected by high drying temperatures if evaporating capacity remains low. The kinetic model developed by the authors describes head rice yield accurately, with an error of 6%.