Studies On Vacuum-microwave Drying Tilapia Slices

Tilapia is known of the fish of21st century. Tilapia is delicious and nutritious. China is one of the most important countries of exporting tilapia production. With growth in the living standard, people demands for various products with high quality. As a new Approach of drying, vacuum-microwave drying gathers advantages of both microwave drying and vacuum drying. Under vacuum-microwave drying, water evaporates quickly. Compared with hot air drying, it not only takes less time but also make out production with higher quality. During drying, water in materials was polarized and release energy. In vacuum environment, water evaporated easier than in atmospheric pressure.In this paper, we compared four kinds of drying methods (hot air drying, microwave drying, vacuum-microwave drying and freeze drying) on effect of tilapia slices quality (L, shrinkage rate, rehydrate rate, recover rate, odor, microstructure). It is found that vacuum-microwave dried tilapia slices are on a par with freezing dried ones, which is much better than hot air dried ones and microwave dried ones.Vacuum-microwave drying of tilapia slices under different vacuum (0.03to0.09MPa) and different microwave power (4to12w/g) were investigated. Results showed that the higher microwave power is, the more obviously MR decreased. The higher the vacuum is, the smaller MR is at the end of drying. Meanwhile, the power of microwave had less noticeable influences under high vacuum. In addition, the suitable mathematical model which can be used to describe the relationship of moisture ratio and drying time was established in this paper. The results showed that the model of Page is the most suitable model to predicted the best representation of the experimental data. After comparison of fitting curves and the observed values, we find out the model of Page is good at fitting Tilapia slices during vacuum-microwave drying.In this study, the quality of vacuum-microwave drying tilapia slices was investigated. A response surface methodology (Box-Behnken) was applied to analyze the influence of the process variables (vacuum degree, microwave power, and size) on the quality (L, shrinkage rate, rehydrate rate and recover rate). Based on the experimental results and RSM analysis, the optimal conditions of this process were determined as:microwave power is9.55w/g, vacuum degree is0.09MPa and size is478.26mm2.