Effects of intermittent CO 2 convection under far‐infrared radiation on vacuum drying of pre‐osmodehydrated watermelon

BACKGROUND Watermelon, a tropical seasonal fruit with high nutrient content, requires preservation through drying due to its perishable nature. Nevertheless, drying of watermelon through conventional processes has a negative impact either on the drying time or on the final product quality. In this work, osmotic dehydration of watermelon followed by far‐infrared radiation‐assisted vacuum drying ( FIRRAVD ) was optimized to develop dehydrated watermelon with minimum moisture content. Significantly, during FIRRAVD , an attempt was made to further intensify the drying rate by forced convection through intermittent CO 2 injection. Drying kinetics of each operation and physicochemical qualities of dried products were evaluated. RESULTS FIRRAVD was a viable method of watermelon drying with appreciably high moisture diffusivity ( D eff,m ) of 4.97 × 10 −10 to 1.49 × 10 −9 m 2 s −1 compared to conventional tray drying. Moreover, intermittent CO 2 convection during FIRRAVD ( ICFIRRAVD ) resulted in appreciable intensification of drying rate, with enhanced D eff,m (9.93 × 10 −10 to 1.99 × 10 −9 m 2 s −1 ). Significantly, ICFIRRAVD required less energy and approximately 16% less time compared to FIRRAVD . The quality of the final dehydrated watermelon was superior compared to conventional drying protocols. CONCLUSIONS The novel CO 2 convective drying of watermelon in the presence of far‐infrared radiation demonstrated an energy‐efficient and time‐saving operation rendering a dehydrated watermelon with acceptable quality parameters. © 2017 Society of Chemical Industry