The study of shrimp drying by greenhouse drying combined with low humidity air

The objective of this research was to examine the qualities of shrimps dried by a process of solar drying combined with low humidity air (45 %Rh, 30 C). In the study, the shrimps were dried in solar dryer (greenhouse dryer) during daytime followed by drying in climate controlled system, which is coordinated with air conditioner, during the night. The low air temperature and relative humidity drying system consists of the humidity control unit (ultrasonic), airconditioner, temperature and relative humidity sensors, heating coil, and microcontroller unit. For low-temperature drying process, the climate control system controls the compressor in the air conditioner by turning the compressor on-off to control the temperature and relative humidity in the chamber. The dehumidification process controls the surface temperature of the evaporator coil close to the dew point temperature, making water vapor in the air condensed to be water drops. The physical properties of the products such as color, hardness, temperature and moisture content were evaluated. The result shows that the greenhouse combined with low humidity air drying takes 16 hr drying time to reduce the 380% initial moisture content to the 14% (d.b) final moisture content of the shrimp. The average temperature and relative humidity in the solar dryer were 45 C and 47% Rh during a daytime. At night, the low-temperature and low–Rh drying system kept the temperature in a range of 28-30C and relative humidity at 40-45 %Rh for drying shrimp. The average temperature and relative humidity for drying were at 29.25C, 42.58% Rh. The qualities of color was 34.51 ± 5.03. Compared with other drying methods, there was no significant difference (p>0.05) in this quantity. However, the highest shading value of 152.45 Newton was found by drying using the greenhouse drying combined with low moisture drying.