Comparative study of microwave-vacuum and vacuum drying on the physicochemical properties and antioxidant capacity of licorice extract powder

Licorice is the dried root of Glycyrrhiza plants, which have longbeen used as flavourings, sweeteners, demulcents and expectorants in Western countries; as anti-allergic and anti-inflammatory drugs in China and Japan; and as therapeutics for diseases, such as cancers, heart disease and diabetes, in Russia and Eastern Europe. Licorice extract powder is the aqueous extract of licorice. Lycyrrhizic acid and flavonoids are the main bioactive constituents of Licorice extract powder that have health functions. Two drying methods, vacuum drying and microwave vacuum drying, were comparatively studied to determine their impact on the physicochemical and antioxidant capacity of licorice extract powder, including its water-solubility, hygroscopicity, flowability, compression moldability, disintegration time, GA and total flavonoids compound contents and antioxidant capacity. The results showed that the physicochemical and antioxidant capacity of licorice extract powder were affected by the drying method. Microwave-vacuum drying maintained the GA and flavonoids components contents as well as the antioxidant capacity and reduced hygroscopicity. However, microwave-vacuum dried powders had a lower water-dissolution and a longer disintegration time than powders tablets. (C) 2017 Published by Elsevier B.V.