预处理对无核白葡萄热风干燥特性的影响

Effect of Pretreatment on Hot Air Drying Characteristics of White Seedless Grapes

为研究预处理对无核白葡萄热风干燥特性的影响,用5 g/100 mL碳酸钾和0.6 g/100 mL橄榄油混合液浸泡无核白葡萄,进行不同干燥温度条件下的热风干燥实验。然后对4种常见的农产品薄层干燥模型进行非线性拟合,并比较评价决定系数(R2)、卡方(χ2)值和标准误差(RMSE)。结果表明:Parabolic模型更加适合描述无核白葡萄热风干燥水分比与干燥时间之间的关系。在干燥温度分别为50、60、70℃时,预处理组的干燥时间比对照组的干燥时间分别缩短33.3%、19.2%、15.4%。预处理组的无核白葡萄的有效水分扩散系数分别提高47.4%、32.0%、32.4%;预处理组的平均活化能比对照组降低16.1%。预处理组葡萄干制品的复水率大于对照组。干燥前预处理可以缩短干燥时间、提高物料有效水分扩散系数、降低干燥活化能和保持干制品良好品质。

The effects of pretreatment by soaking in a mixed solvent system containing 5 g/100 mL potassium carbonate and 0.6 g/100 mL olive oil and hot-air temperature （50, 60 and 70 ℃） on drying characteristics of white grapes were studied using a hot air dryer. Non-linear regression analysis was used to develop four common agricultural thin layer-drying models based on the data obtained and these models were evaluated by coefficient of determination （R2）, chi-square value （;（2） and root mean squared error （RMSE）. It turned out that the Parabolic model was more appropriate to describe the relationship between moisture ratio and drying time. Compared with the control group, the drying time for the pretreatment group was shorten by 33.3%, 19.2% and 15.4% at 50, 60 and 70 ℃, respectively, the effective diffusivity of white grapes was increased by 47.4%, 32.0% and 32.4%, respectively. In addition, the activation energy was decreased by 16.1%, and the rehydration of 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.