Alternative economic and shortened method for the production of dried germinated rice

Abstract

Since germination creates chalky grain around the entire surface of the kernel, it is commonly eliminated by steaming germinated paddy before drying. In this work, a continuous fluidized bed with a capacity of 100 kg/h was therefore used to treat the chalkiness with high-temperature hot air. The performance of this dryer in terms of water evaporation capacity and energy consumption along with the quality attributes was determined quantitatively. Two crops of Khao Dawk Mali 105 stored for 1 month and 8 and 9 months were used as the raw material. Hot air at temperatures of 130–150 °C with full recycling of the exhaust air was able to eliminate the chalkiness perfectly. The best performance, as indicated by higher water evaporation capacity and lower energy consumption, was obtained at a higher feed rate, higher bed depth and higher drying temperature. The higher bed depth and drying temperature provided a higher degree of starch gelatinization and the correspondingly higher head brown rice yield and hardness of the cooked germinated brown rice except for stickiness. Within the studied drying temperature range, the amount of accumulated gamma-aminobutyric acid after drying the rice which had been stored for 1 month decreased slightly compared to that of the sun-dried product, in a range of 11.4–12.6 mg per 100 g, and decreased significantly for the rice which had been stored for 8 and 9 months. The storage period also influenced the texture after cooking. It is recommended that to obtain the premium quality from the germinated product, the paddy should be stored for 1 month, and a drying temperature of approximately 130˚C should be applied. Under the recommended conditions, the energy consumption was about 1.13 MJ/kg of paddy, and the operating cost of the continuous fluidized bed was 0.17 USD/kg, which was more economical than that of the conventional method.

Keywords:

• Chalkiness
• GABA
• germinated rice
• energy consumption
• fluidized bed dryer

Acknowledgements

The author thanks to the learning centre for increasing agricultural production efficiency for providing material and location for testing pilot scale fluidized bed.

Additional information

Funding

The authors express their sincere appreciation to Thailand Research Fund (Grant no. DPG 5980004 and RGU 6180004 and RTA 5880009) for their financial support.