Abstract
To reveal the vacuum drying mechanism of aqueous extracts and develop vacuum drying processing to provide theoretical guidance for Lonicera japonica Thunb. aqueous extracts, the effects of vacuum pressure (10, 15, 20, 25, 30 kPa), drying temperature (80, 90, 100, 110, 120 °C), and material thickness (2, 4 mm) of vacuum drying on the moisture ratio, drying rate, material temperature, moisture effective diffusivity, activation energy, content and distribution of moisture, water-solubility, flowability, antioxidant capacity, and the contents of chlorogenic acid and galuteolin contents were investigated. Results showed that the drying mechanism of the aqueous extracts was different from that of conventional porous media, which contains drying stagnation and boiling phenomenon. The initial bound water content of the aqueous extracts was 100%, and the bound water will not convert to free water during vacuum drying. The best vacuum drying process for the L. japonica Thunb. aqueous extracts was 30 min, 4 mm, 120 °C and 10 kPa.