Investigation of ultrasound pretreatment time and microwave power level on drying and rehydration kinetics of green olives

Abstract In this study, the effect of ultrasound (US) combined microwave (MW) drying of green olive slices was studied. Olive samples were exposed to ultrasound (5 and 10 minutes; 32 KHz) at room temperature before dried at microwave at 3 different power level (180W, 450 W and 800 W). The drying and rehydration characteristics and quality parameters of olives were determined by comparing with obtained by non-ultrasound pretreated MW dried samples. Midilli et al and Diffusion models were the most suitable models for US-MW drying with the highest R2, and lowest RMSE and chi square values. Total phenolic compounds (TPC) of olive slices reduced during drying in all treatments, however TPC of ultrasound pretreated samples were relatively higher those non treated samples dried at same microwave. Increasing of microwave level and ultrasound time decreased the total drying time up to B.5. This study showed that US-MW can be a useful combine drying method for olive slices which decreased the drying time and improved the qualitative properties of olives.

摘要 本研究探究了超声（Ultrasound, US）联合微波（Microwave, MW）干燥青橄榄片的应用效果。将橄榄样品置于室温环境下，分别经5分钟、10分钟的32kHz超声预处理后，再以180W、450W、800W三种不同功率的微波进行干燥。通过与未经超声预处理的微波干燥样品的测试结果对比，测定了橄榄的干燥特性、复水特性及品质参数。Midilli模型与扩散模型是适配US-MW干燥工艺的最优拟合模型，其决定系数（R²）最高，均方根误差（RMSE）与卡方值均最低。所有处理组的橄榄片总酚类物质（Total Phenolic Compounds, TPC）在干燥过程中均出现含量下降，但经超声预处理的样品总酚含量相对高于相同微波功率下未预处理的样品。微波功率提升与超声处理时长延长可将总干燥时长缩短至多B.5。本研究表明，US-MW联合干燥法可有效缩短青橄榄片的干燥时长并改善其品质特性，是一种极具应用潜力的橄榄片干燥工艺。