Study on vacuum drying kinetics and processing of the Lonicera japonica Thunb. aqueous extracts

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 degrees 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 degrees C and 10 kPa.

Automated summary

This study investigated the vacuum drying mechanism of Lonicera japonica Thunb. aqueous extracts and found that it differs from the drying mechanism of conventional porous media. The optimal vacuum drying process for the aqueous extracts was determined to be 30 minutes, 4 mm thickness, 120 degrees Celsius temperature, and 10 kPa pressure.