Drying and Quality Characteristics of Flos Lonicerae in Modified Atmosphere with Heat Pump System

Abstract

AbstractModified atmosphere drying of Flos Lonicerae is conducted, and the effects of drying temperature and oxygen content on drying characteristics and product quality are investigated in this study. Nitrogen gas is aerated into the dryer to adjust the oxygen content, and a heat pump system is used to control the drying temperature. The results showed that the increase in drying temperature and the decrease in oxygen content could improve the drying rate and effective moisture diffusivity. Increase in chlorogenic acid and chlorophyll contents as well as decrease in color difference were observed with decreasing drying temperature and oxygen content. High product quality could be achieved at all drying temperature levels when oxygen content was as low as 5%. Therefore, reducing oxygen content in the drying atmosphere is an effective method to improve product quality.Practical ApplicationA modified atmosphere dryer equipped with a heat pump system is developed. The effects of drying parameters, including drying temperature and oxygen content, on drying characteristics and quality of Flos Lonicerae are studied. Nitrogen gas is used to replace certain portions of air to achieve different oxygen content levels in drying processes. The results show that drying under low oxygen content increases effective moisture diffusivity (Deff). It also promotes higher chlorogenic acid and chlorophyll contents as well as better product appearance. Therefore, modified atmosphere drying is a promising method to protect the quality of dried products. The results of this study are helpful to the technological application of modified atmosphere drying with heat pump system for Flos Lonicerae dehydration and preservation.