Physical changes and mechanism of whole litchi in the process of intermittent microwave drying

The objective of this study was to discuss the mechanism of heat and mass change on whole litch and evaluate the physical changes in microwave drying. Based on the analysis of the drying rate of litchi,energy consumption,temperature gradient,browning and pulp shrinkage,physical changes on drying litchi process and corresponding mechanism was studied and discussed in this paper. This study proved that the intermittent drying technology of microwave drying on whole litchi had the advantages of fast drying,high semi-dried litchi pulp quality advantages,low energy consumption,simple device and process. Experiments showed that considering the comprehensive physical changes including energy consumption,color,shrinkage,hardness and texture conditions,microwave power 700 W 7s/65 s heating interval time was the best technology.Meantime,energy consumption was 2.11,and litchi pulp had uniform gold color,in which L*,a*,b* values were separately 37.5,14.4 and 16.4. With flash shrinkage coefficient followed nearly linear shrinkage expansion/contraction,no obvious depression disappeared on surface. Meanwhile,it also helpd choosing proper microwave drying method,and gave reference to the establishment of the computer simulation model of microwave drying of litchi moisture and temperature change.