Development and evaluation of hot air‐assisted microwave dryer for shrimp ( Metapenaeus dobsoni )

Abstract

The study aimed to develop a hot air-assisted continuous microwave (HAMW) drying system and evaluate the drying of shrimp under microwave radiation. The drying system comprised of a drying chamber with a conveyor belt of dimension 1.5 × 0.5 m, magnetron of 1.45 kW to generate microwaves at frequency of 2450 ± 50 MHz, hot air generation system with air heater of 1 kW and axial fan of 50 W and other controls. Moisture content of shrimp was reduced from 80.55% to 16.5% within 3.5 h of drying. Volumetric heating effect of microwaves resulted in reduction of drying times. Effective moisture diffusivity of microwave-dried shrimp was found to be 6.7 × 10−7 m2/s. Page model was the suitable fit for the data under study (R2 = 0.998454, RMSE = 0.0.01552 and χ2 = 0.000134). The drying efficiency and specific energy consumption for hot air-assisted microwave drying of shrimp were calculated to be 35.71% and 1.75 kWh/kg, respectively. Water activity, rehydration ratio and shrinkage of the dried shrimp samples were 0.552%, 2.51% and 14.14%, respectively, with maximum color retention. Proximate and microbiological analysis of fresh and dried shrimp were carried out and were found to be under safe limits. The developed HAMW drying system was found to be suitable for shrimp drying under controlled conditions. Practical applications Hot air-assisted microwave (HAMW) drying system was developed to cater drying of shrimp under controlled conditions with lower drying times. Specific energy consumption (1.75 kWh/kg), drying efficiency (35.71%) and effective moisture diffusivity (6.7 × 10−7 m2/s) during drying was found to be superior to convective drying. Evaluation of quality parameters of dried shrimp such as rehydration ratio (2.51), shrinkage (14.14%), water activity (0.552) and total plate count (2 × 104 CFU/g) was falling under acceptable limits. The study suggests HAMW drying system as a potential means of drying shrimps for large-scale commercial production.