Microwave drying is a rapid dehydration technique that can be applied to preserve agricultural products. For its complex application environment, the temperature and humidity in the drying material cannot be precisely controlled during microwave drying process. However, microwave drying without exactly controlling temperature and humidity is unable to guarantee the quality of agricultural products. To achieve a high quality, this paper proposed a fuzzy control method for the microwave dryer, which could control the temperature and humidity precisely. To identify the dry effect of the proposed fuzzy control scheme, drying time of Chinese jujube during fuzzy microwave (FM) drying, ordinary microwave (OM) drying, and temperature microwave (TM) drying were investigated, quality attributes such as vitamin C (VC), color and total flavonoids content (TFC) of dried samples were evaluated. As the results showed, total drying time used to reduce 500 g jujube moisture content from 74% to 6% on dry basis required 30, 26, and 31 min using FM drying, OM drying and TM drying, respectively. The drying rate with FM drying was the fastest. Jujube dried by FM drying revealed better color and higher retentions of VC and TFC content than TM and OM drying. Compared with TM and OM drying, FM drying performed shorter drying time and better quality of samples, indicating that microwave dryer with fuzzy controller can provide a practical and effective method for drying jujube with acceptable product quality.
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