عنوان مقاله English
Drying is one of the most important steps in raisin processing. Achieving optimum drying conditions can affect the processing time and improvement of raisin quality. In this research, effect of two-temperature and pretreatments on time and drying rate of Black currant grape were studied. Drying was performed in two ways: In the first one, temperatures was constant at four levels of 50, 60, 70, and 80 ºC and in the second one sample were placed at two temperatures. In the latter, samples were placed at 80 ºC and when moisture content was reduced to 50%, temperature was set to 70, 60 and 50 ºC. Four pretreatments including hot water, %5 potassium carbonate, %0.4 olive oil, %0.5 sodium hydracids and no pretreatment were performed. According to the results of the ANOVA, factors such as temperature, two-temperature and pretreatment have significant effects on drying time and average drying rate. Drying time of grape with two-temperature comparing with drying time of constant temperature was decreased up to 67% for some pretreatment. Maximum and minimum activation energy were determined 2893.9, 4538.8 kj/kg.
کلیدواژهها English
