Abstract
The water content of unhulled rice is conventionally measured by the ordinary pressure drying method and the electrical resistance method. In the former method 5 g of crushed specimen is dried at 106.5±1 ˚C for five hours (referred to as 105ºC method). The latter is a method using the electricity type water meter guaranteed for the measurement precision within 0.5% of the standard error of the 105˚C method. On the other hand, a halogen moisture analyzer with high accuracy and low cost properties has been developed in recent years. However, the drying of unhulled rice by this analyzer has not been reported. This study was carried out to clarify the setting conditions of measuring the water content of unhulled rice using a MOC63u moisture analyzer equipped with a halogen heater in relation to the weight of the sample and the measurement mode (drying mode, measurement ending mode). As a result, the optimum measurement condition was programmed with ∆W1 and ∆W2 in rapid mode using 5 g of ground sample where ∆W1 denotes the change in water rate of 0.5% 30 s-1 at the maximum temperature for rapid drying, and ∆W2 denotes that of 0.03% 30 s-1 at 135ºC at the end of drying. The value obtained using this method showed deviation of 0.06 ± 0.07% (mean value ± standard error) from the value obtained by the 105ºC method which was closely related with that obtained with 10 g kernel by the 135ºC-24 hr method. The proposed method can markedly reduce measurement time to 8 min and 18 s (498 ± 21 s, mean value ± standard error) compared with the 5h in the 105ºC method. It was concluded that this method is widely applicable for the measurement of water content of unhulled rice for investigation of yield.
