Ultrasonic pretreatment of carrot slices: Effects of sonication source on drying kinetics and product quality

Abstract: In this study effects of ultrasonic pretreatment with different sonication sources on drying behavior of carrot slices were evaluated. Fresh carrot slices were pretreated with ultrasonic probe at 65, 75 and 85 W or ultrasonic bath at 10, 20 and 30°C for 3, 5 and 10 min before air drying. Water gain % and solid loss % of pretreated samples were calculated and color values, β-carotene content and rehydration ratios of dried samples were determined. Drying behavior of the pretreated samples was evaluated and the drying data were fitted to thin layer drying models. Constant drying rate period was not observed for the carrot slices; however two definite falling-rate periods having different slopes were obtained. Drying time was significantly reduced (up to 20%) depending on the type of pretreatment. The redness value, total color difference and Chroma values of pretreated and control samples were in the same group (p>0.05). β-carotene content of ultrasonic bath pretreated samples were significantly higher than the samples pretreated with ultrasonic probe and the sample dried without any pretreatment as well (p<0.05). Also rehydration ratios of control samples were found lower than the ultrasound pretreated samples.

摘要：本研究评估了不同超声源预处理对胡萝卜片干燥特性的影响。将新鲜胡萝卜片分别采用功率为65、75、85 W的超声探头（ultrasonic probe），或温度为10、20、30℃的超声水浴（ultrasonic bath）预处理3、5、10 min后，进行热风干燥。计算了预处理样品的水分增重率与固形物损失率，并测定了干燥样品的色泽参数、β-胡萝卜素（β-carotene）含量及复水比。对预处理样品的干燥特性进行了评估，并将干燥数据拟合至薄层干燥模型（thin layer drying models）。结果表明，胡萝卜片未出现恒定干燥速率阶段，但存在两个斜率各异的明确降速干燥阶段。不同预处理方式可显著缩短干燥时间，最高可缩短20%。预处理组与对照组的红度值、总色差及彩度值无显著统计学差异（p>0.05）。超声水浴预处理样品的β-胡萝卜素含量显著高于超声探头预处理样品及无任何预处理直接干燥的样品（p<0.05）。此外，对照组样品的复水比低于超声预处理样品。