热风和微波干燥对龙眼品质的影响

Changes in the Quality of Dimocarpus longan During the Hot-Air Drying and Microwave Drying Processes

摘要:

为了获得品质优良的龙眼干制品，研究分析了龙眼果肉在热风和微波两种干燥过程中的品质变化。结果表明，两种干燥方法下果肉褐变度变化均与多酚氧化酶（PPO）活性相关；过氧化氢酶（POD）活性的激活与果肉水分质量分数相关；PPO对温度的敏感性高于POD；抗坏血酸褐变不是引发果肉褐变的主要原因；双层堆积厚度下微波干燥较均匀，制得龙眼质构较优。通过对比分析，微波干燥的效率显著高于热风干燥，且微波干燥下果肉褐变度及PPO活性均低于热风干燥，故微波干燥法比热风干燥法更适合用于龙眼干燥加工。

Abstract:

The changes in quality of longan during the hot-air and microwave drying processes were investigated in this study. As a result，the change in browning degree of the longan pulp was closely related to the polyphenoloxidase（PPO） activity. The activation of peroxidase（POD） activity had a connection with the water content of longan pulp. PPO was more sensitive to high temperature than POD. The browning of ascorbic acid was not the major reason for the browning of longan pulp. Microwave drying was well-distributed when two-layer of fresh longan was placed in the microwave chamber. The longan dried by microwave was acceptable in texture. By comparison，the efficiency of microwave drying was significantly higher than that of hot-air drying and the browning degree and PPO activity of the longan dried by microwave drying were both lower than those of the longan dried by hot-air drying. Therefore，microwave drying is more suitable for the drying process of longan than hot-air drying from the viewpoint of quality and time-saving process.