Chupawa Prarin, Suksamran Wanwisa, Jaisut Donludee, Ronsse Frederik, Duangkhamchan Wasan
Research Unit of Mechatronics Engineering, Faculty of Engineering, Mahasarakham University, Kamriang, Kantarawichai, Maha Sarakham 44150, Thailand.
Research Unit of Smart Process Design and Automation, Mahasarakham University, Kamriang, Kantarawichai, Maha Sarakham 44150, Thailand.
Foods. 2022 Dec 14;11(24):4045. doi: 10.3390/foods11244045.
Stepwise drying is an effective technique that promotes energy saving without additional capital cost. The stepwise drying mode was investigated for energy consumption and dried product qualities using a coupled heat and mass transfer model associated with kinetics equations of volume shrinkage and degradation of β-carotene in carrot cubes. Simulations were performed using a finite element method with extension of a chemical species transport. Validation experiments were carried out under constant drying modes at 60 °C, 70 °C and 80 °C using a lab-scale convective hot air dryer. The verified models were subsequently employed to investigate the effects of two step-up drying modes (60 to 70 °C and 60 to -80 °C). The optimal drying condition was determined using the synthetic evaluation index (SI) with criteria of high specific moisture evaporation rate (SMER), low shrinkage ratio and β-carotene degradation. Simulated results showed comparable agreement with experimental data of moisture content, shrinkage ratio and β-carotene ratio. Step-up drying of 60 to 70 °C gave the highest SMER of 0.50 × 10 kg of water evaporated per kWh, while the operation at constant temperature of 80 °C gave the lowest value of 0.19 × 10 kg of water evaporated per kWh. Model-predicted results showed less shrinkage of carrot cubes, but higher degradation of β-carotene under step-up drying compared to single-stage drying under temperature of 60 °C. Based on the highest SI value (0.36), carrot cubes were optimally dried under step-up mode of 60 to 70 °C.
逐步干燥是一种有效的技术，可在不增加资本成本的情况下促进节能。利用与胡萝卜块中β-胡萝卜素体积收缩和降解的动力学方程相关的传热传质耦合模型，研究了逐步干燥模式下的能耗和干燥产品质量。使用扩展了化学物质传输的有限元方法进行模拟。在60℃、70℃和80℃的恒定干燥模式下，使用实验室规模的对流热风干燥机进行验证实验。随后，使用经过验证的模型研究两种升温干燥模式（60至70℃和60至80℃）的效果。使用综合评价指标（SI），以高比水分蒸发率（SMER）、低收缩率和β-胡萝卜素降解为标准，确定最佳干燥条件。模拟结果与水分含量、收缩率和β-胡萝卜素比例的实验数据具有可比性。60至70℃的升温干燥具有最高的SMER，为每千瓦时蒸发0.50×10千克水，而80℃恒温运行时的值最低，为每千瓦时蒸发0.19×10千克水。模型预测结果表明，与60℃单阶段干燥相比，升温干燥下胡萝卜块的收缩较小，但β-胡萝卜素的降解较高。基于最高的SI值（0.36），胡萝卜块在60至70℃的升温模式下实现了最佳干燥。
