Experimental Study On The Carica Papaya Microwave Drying Characteristics In Thin-Layer

Fresh carica papaya is known as the king of all kinds of fruits, which is highly nutritive and healthy for human. During the past several years, the output of carica papaya has been mushrooming in tropical and subtropical zone in China, whereas the preserving technique still lags behind. At present, insolating in the sun or hot air drying are the main drying modes, which are inefficient and of inferior quality for dried products, and restrict the growth of economy in tropical and subtropical zone. Thus, it is critically important to develop more efficient technique for carica papaya preserving. In this study, microwave drying was firstly introduced for the drying of carica papaya. Microwave drying theory and quality changes of dried product were explored and better parameters was obtained. Furthermore, comparisons and combinations between hot air drying and microwave drying were conducted.The microwave drying was carried out at first. It showed that the drying rate obviously increased and the quality of dried papaya was improved. During lower power the drying process basically included pre-heating, constant rate and falling rate periods. As the power was high enough, dehydrating mainly took place in heating period, and the constant rate period disappeared. The semi-empirical Page's equation used to describe the drying kinetics of dried slice materials gave an excellent fit for all data points, where the drying constant k and n were depended on the microwave power per mass.The quality of product by microwave drying was also studied. It was influenced by microwave power, slice thickness and shape to different extent. In general, better quality could be achieved by increasing microwave power, but it would change to be worse as the power exceeded 462W. The thinner was papaya slice, the better was the quality. The straight-cut sample was better than crosscut as far as dried product quality was concerned, but the drying rate was reversed. Therefore the shape should be decided by balancing between the quality and the drying rate.The study of comparisons between hot air drying and microwave drying showed that microwave drying resulted in substantial saving of processing time, nice rehydration...