The Research Of Combined Drying Tecnique For Leisure Dehydrated Fruits And Vegetables

This study compared various drying operations for fresh fruits and vegetables in terms of drying energy consumption and product quality, designed a combination drying process using freeze drying in the initial phase and vacuum microwave in the final phase, experimentally optimized and mathematically modeled the whole process, and established the thin layer drying model. The optimum drying process thus established provide satisfactory product quality, lower power consumption, and improvements in equipment productivity.The drying effects of freezing, vacuum microwave, and combination freeze & vacuum microwave drying were investigated on apples, carrots and strawberries in terms of drying energy consumption, vitamin C retention, puffing, color, textural characteristics, and sensory evaluation. The results showed that, whether they were apples, carrots or strawberries combination freeze & vacuum microwave drying greatly lessened drying time and significantly shortened energy consumption. Compared to freeze drying, combination drying saved energy consumption more than 40 %. Vitamin C retention rate, color and texture characteristics achieved a level of freeze-dried products. But puffing and anti-moisture absorption was better than simple freeze-dried products. Therefore, combination freeze & vacuum microwave drying deserves promoted application both for economical and product quality considerations.Because energy consumption and production quality were most concerned by the enterprises and consumers. In order to obtain the reduce energy consumption, measures must be taken. Freeze drying has advantages of distillation to remove most water of materials in low temperature and the greatest extent possible to retain the characteristics of the original materials during the initial drying phase. The final drying phase use of vacuum microwave drying of the characteristics of high-intensity, can effectively remove residual moisture, reduce the quality of the material damage, and expand the inside organization. Two advantages make up each other, combination drying avoid the shortcomings of a single drying way. Howere, combination drying consisted of freeze drying followed by vacuum microwave drying will fundamentally solve these problems. Fuji Apples were choosed as the experiment materials. A three-factor, three-level combined experimental design, was chosen to evaluate dependent variables affecting energy consumption, vitamin C retention rate, anti-moisture and sensory evaluation by Response Surface Methodology(RSM). The drying process parameters were optimized and obtained.Fuji Apples were choosed as the experiment materials. The changes in moisture content, MR and drying rate were examined during freeze drying and vacuum microwave drying, respectively. Linear regression and multiple linear regression procedures were used to estimate the parameters associated with the drying models, from which a semi-empirical mathematical model was developed for predicting the thin layer drying kinetics of apple chips during combination drying.