Abstract:

To improve the drying productivity and the quality of dried fruits, and to decrease the drying energy consumption, experiments were conducted to study the microwave-vacuum drying characteristics of strawberry slices and the quality of their dried products. The quadratic regression orthogonal design method was employed to establish regression mathematical models describing the relationships between the rehydration ratio of dried strawberry slices, vitamin C retention ratio or the energy consumption durinzg drying and drying power, sample thickness and drying chamber pressure. The effects of these variables on these functions were dealt with. Decreasing sample thickness and drying chamber pressure and increasing drying power could individually result in a higher dehydraation rate. The rehydration ratio of dried strawberry slices and vitamin C retention ratio became both higher, with increasing sample thickness or decreasing drying chamber pressure. The energy consumption during drying tended downward, as sample thickness and drying power increased or drying chamber pressure increased. The optimum process parameters for drying strawberry slices were determined by multivariable nonlinear optimization method as follows: drying power, 6.18 W/g; sample thickness, 5.05 mm; and drying chamber pressure, 55.19 Pa.

Key words: strawberry slices, microwave-vacuum drying, energy consumption, quality