Drying of Rough Rice (II)

The relation between drying conditions and rice qualities

Abstract

The effects of drying airflow rates, drying air temperatures and drying times on rice qualities such as checking, germination and gloss were determined for rough rice in multi-stage drying.
The tests were performed in 11cm deep static bed on 4 varieties of rice grown in Hokkaido, useing the laboratory scale drier equipments reported in Part I of this study.
1. The relationship of these three drying factors with the percent of checked kernels les to the conclusion that number of checked kernels decreased with increase of drying rates. Here, the drying rate means reduced moisture content divided by total heating time in hour.
2. It was found that temperature of rice in drier was closely related to number of checked kernels, so that temperature of rice could be considered as an index for safe operating schedule under any drying conditions. Data indicated that the safe limit of temperature of rice was 35°C.
3. Nnmber of checked kernels after drying increased continuously up to 48 hour after leaving the drier.
4. When temperature of rice in drier rises over 40°C, rate of germination decreased sharply.
5. Gloss of hulled or milled rice, dried under the condition of rice temperatures below 40°C, was not affected by heating.
It has been demonstrated in many modern drying plants that these laboratory-scale experiments could be applied successfully on a commercial scale.