Abstract:

As an alternative to conventional electronic oven heating, microwave technique was used for the dehydration of peanuts. Dehydration characteristics of peanuts during microwave treatment under different microwave powers and material loads were investigated for providing experimental evidences for the use of microwave dehydration in the production of dried salted peanuts. Microwave dehydration of peanuts was shown to consist of two stages, i.e., two dehydration peaks. The appearance time of dehydration peaks and the maximum dehydration rate were affected by material load and microwave power. Based this investigation, a Box-Benhnken central composite design involving 3 variables (microwave power, material load, microwave treatment time) at 3 levels was employed to optimize dehydration rate, unit electricity consumption and sensory quality with respect to the production of dried salted peanuts. In the optimization, Design expert 7.0.1 was used and regression models for the above indicators were developed. Results showed that significant effects of microwave power, material load, microwave treatment time on dehydration rate and unit electricity consumption were observed, and material load had a significant effect on sensory quality. The optimal values of these parameters were as follows: microwave power 800 W, material load 54.25 g, microwave treatment time 3.5 min. Under such conditions, dehydration rate, unit electricity consumption and sensory quality score were 5.79 g/min, 0.76 kW·h/kg and 9.17, respectively.

Key words: peanuts, microwave, dehydration characteristics, regression equation