Optimization of Short- and Medium-Wave Infrared Drying and Quality Evaluation of Jujube Powder

In this study, response surface methodology was used to optimize parameters of short- and medium-wave infrared drying processing for producing jujube powder. Optimization factors were power input (675–1,575 W), drying temperature (70–90 °C) and drying time (2.5–3.5 h), and responses were moisture content, L value, b value and vitamin C content of the jujube powder. Box–Benhnken center design was applied to the optimized the processing conditions. The optimal conditions for the production of jujube powder by the short- and medium-wave infrared drying method were power input of 1,125 W, drying temperature at 85.4 °C and drying time for 3.5 h. Under the optimal conditions, the values of moisture content, L, b and vitamin C content of jujube powder were 4.59 %, 64.46, 19.87 and 441.56 mg/100 g, respectively. Quality evaluation of the jujube powder was also investigated. The results were: hygroscopicity of 28.83 %, rehydration of 236.44 %, solubility of 53.59 %, bulk density of 0.70 g/ml, particle size of 154.2 μm, soluble solids content of 82.29 %, total sugar content of 46.87 %, reducing sugar content of 32.09 %, total acid content of 2.03 %, total flavonoids content of 1.45 % and cyclic adenosine monophosphate content of 75.32 mg/kg. The microstructure of jujube powder was irregular and 38 kinds of aroma components were generated.