Drying Kinetics and Quality Change Law of Perilla during Intelligent Dehumidification Drying Process

In order to clarify the characteristics of Perilla during the process of post-harvest drying, the drying characteristics and quality changes of Perilla stems and leaves at different drying temperatures were studied by using a drying device with intelligent moisture removal. The dry basis moisture content change and drying rate curve of Perilla stem and leaf during drying in the temperature range of 50~80 ℃ were given, and the drying data were fitted by mathematical model. The quality differences among dried Perilla at different temperatures, freeze-dried and natural dried perilla were compared, including volatile oil content, rosmarinic acid content, total flavonoids and total phenols content and antioxidant capacity. The changes of volatile flavor were analyzed by ultrafast gas phase electronic nose analysis system. Based on the above indexes, the quality differences of perilla with different drying methods were comprehensively evaluated. The results showed that the drying process of Perilla leaves was always in the slow drying stage, while the stems of perilla experienced three drying stages: Increasing speed, constant speed and decreasing speed. The stems and leaves of Perilla were suitable for Page model and Two-term model respectively. Compared with the traditional drying in the shade, the intelligent low-temperature drying (50 ℃) had no significant difference in the content of active ingredients, antioxidant performance, and the content and abundance of odor substances. The content of volatile oil and other substances was better than the natural drying in the shade. Drying temperature is an important factor that affecting the quality of Perilla. The content of active components, antioxidant capacity and flavor substances of Perilla decreased with the increasing of temperature.