Optimization of Process Parameters for Microwave – Convective Drying of Grapes using Response Surface Method
Drying is a key method to preserve agricultural food products. The longer drying time in many conventional
drying methods at relatively elevated temperature during the falling rate periods leads to undesirable degradation of the
finished products. Microwave drying shorten the drying time drastically and improves the desirable sensory quality of final
product. In This study combination of convective hot air drying and microwave heating was applied to produce raisins from
grapes in short time duration with desirable quality aspects. The influence of drying parameters such as specific microwave
power, hot air temperature and their interaction were analyzed using response surface method. This research work was
carried out by doing experiments in laboratory drying setup and optimal combination was determined as 450C hot air
temperature and specific microwave power as 0.25 W/g to obtain results in less than 8 hours to constraint the process for
mass production in single industrial working shift. Optimal conditions were used on continuous conveyor drying setup to
confirm the results for mass production.
Keywords - Drying, Response surface method (RSM), Microwaves, Hot air, Grapes.