Study On The Microwave Vacuum Drying Characteristics And Drying Technology Optimization Of Banana Slices

Banana (Musa parasdisac), belongs to Musaceae, Musa, as an important fruit of tropical and semitropical area, it has rich nutrition but no cholesterol. Banana can be used for dispelling thermal and moistening lung, relieving constipation with laxatives, preventing vascular sclerosis, depressurization and sectors, so people like it very much. Banana is a climacteric fruit. Owing to the soft texture and shorter storage period, storage and transport become difficult, it also loses seriously, so dehydration becomes an important method of processing and storage. Microwave vacuum drying technology was applied to banana drying in this paper. The microwave vacuum drying characteristics and the rule of quality changes for banana were studied, and the optimal technology parameters were certained by orthogonal experiment and integrated optimization, then compared with vacuum deepfrying and microwave drying to confirm the feasibility of microwave vacuum drying technology. The purpose of all above was to provide an important recommendation for practical industrialization of banana by microwave vacuum drying.1,Using microwave vacuum drying technique to research the properties of banana slices microwave vacuum drying. The effects of microwave power, vacuum degree and initial moisture content on the drying rate were investigated and the changing rule of moisture during the processes of microwave vacuum drying was got. Microwave vacuum drying course of banana slices could be divided into three stages:speed-up, constant-speed and speed-down. During the drying course, dehydration rate was influenced by some factors, and the influence degree of each factor was different (Microwave power>initial moisture content>slice thickness> vacuum degree). The stronger microwave power was, the quicker dehydration rate was and the shorter drying time was. The drying rate was faster and the drying time was shorter when vacuum degree was higher. However, the higher vacuum degree was not always good. Higher vacuum degree would not only enlarge consumption but also make sparkbreakdown. Within the limits of microwave radiation, thicker slices and lower initial moisture content would get quicker dehydration rate and the short the drying time. 2,Effects of microwave vacuum drying parameters on main quality of banana slices (fragility, expansion rate, color and sensory quality) were studied. With the increase of the vacuum degree, the drying temperature would be decrease, color and sensory quality would be better, and its expansion rate and fragility will be increase; The higer microwave intensity was, the more heat energy absorbed by materials, the faster transpiration rate was, and the higher vacuum degree to promote the power of expansion steam pressure, expansion rate and fragility would be improve, the quality of their senses first increases and then decreased. When microwave intensity was 12W/g the color would be closest to the fresh sample.3,The optimization of microwave vacuum drying for banana slices was studied. Taking color, fragility, expansion rate and sensory quality as evaluation indexes, experimental research of microwave vacuum drying on banana slices were carried out to discuss the influence of vacuum, microwave intensity, slices thickness on the product quality. The optimal technology parameters were defined by orthogonal experiment and integrated optimization, then compared with vacuum frying and microwave drying. The results showed that when vacuum was -80kPa, microwave intensity was 12W/g, and slices thickness was 14mm, dried banana slices of the optimal quality was more superior than vacuum frying's and microwave drying's. For these reasons, using the microwave vacuum drying technology can improve the quality of banana slices. These optimal technology parameters could afford theoretical foundation for industrial application of microwave vacuum drying technique of banana.