Abstract:

The effects of pretreatment by soaking in a mixed solvent system containing 5 g/100 mL potassium carbonateand 0.6 g/100 mL olive oil and hot-air temperature (50, 60 and 70 ℃) on drying characteristics of white grapes were studiedusing a hot air dryer. Non-linear regression analysis was used to develop four common agricultural thin layer-drying modelsbased on the data obtained and these models were evaluated by coefficient of determination (R2), chi-square value (χ2) androot mean squared error (RMSE). It turned out that the Parabolic model was more appropriate to describe the relationshipbetween moisture ratio and drying time. Compared with the control group, the drying time for the pretreatment group wasshorten by 33.3%, 19.2% and 15.4% at 50, 60 and 70 ℃, respectively, the effective diffusivity of white grapes was increasedby 47.4%, 32.0% and 32.4%, respectively. In addition, the activation energy was decreased by 16.1%, and the rehydrationof dried grapes from the pretreatment group was higher. This pretreatment is not only good for shortening the drying time,improving effective moisture diffusivity and reducing activation energy, but also help preserve the quality of dried products.

Key words: grape, pre-treatment, drying mathematical models, moisture diffusivity, activation energy