Effects of ambient air dehumidification, air temperature, and drying duration on rough rice quality and pasting properties using fluidized bed and fixed bed dryers

Abstract

AbstractBackground and objectivesHigh humidity ambient air is a common phenomenon in the United States ​Mid‐​South region, resulting in a delay in the drying process to avoid rewetting rough rice. Ambient air dehumidification could have the potential to overcome this challenge and result in a continuous drying process. Therefore, the present study explored the effects of ambient air dehumidification, air temperature, and drying duration on rough rice quality and pasting properties in a fluidized bed and fixed bed drying systems.FindingsA fluidized bed and a fixed bed drying systems were used to study the effects of dehumidification settings (with and without), air temperature (40°C, 45°C, and 50°C), and drying duration (30 min, 45 min, and 60 min) on rice quality and pasting properties in triplicates. Silica gel was used as a desiccant for ambient air dehumidification. The results showed that the range of moisture removal to be 4.5 to 7.1 (%, dry basis) for 1 hr in a fluidized bed rice drying. The maximum water absorbed by air achieved 0.382 and 0.434 kg for fluidized bed and fixed bed dryers, respectively, after 60 min of drying, at 50°C, and with air dehumidification. The peak viscosity of rough rice was lower for all fluidized bed experiments (2,712.8 cP) than the fixed bed drying experiments (2,815.8 cP).ConclusionsThe results showed that head rice yield and rice whiteness did not reduce in fluidized bed drying significantly than the fixed bed drying. Head rice yield was negatively correlated with rice whiteness. Ambient air dehumidification improved moisture removal from rough rice and can be employed during humid conditions. Pasting properties also supported the notion of attaining good quality rice dried in a fluidized bed system compared with a fixed bed drying system. Head rice yield was positively correlated with the peak and trough viscosities signifying the increase in milling yield with the rice water‐absorbing capacity and resistance to cooking textural breakdown.Significance and noveltyThe study proved that utilizing dehumidified air in a fluidized bed drying system could dehydrate rough rice without reducing quality. The system successfully utilized silica gel to dehumidify ambient air, allowing continuous ambient air in‐bin on‐farm drying of rough rice.