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Glabridin (from licorice) and carnosic acid (from rosemary) are natural phenolic compounds which show the antioxidant and antimicrobial activities. Nevertheless, the use of licorice and rosemary extracts in food matrix is highly limited due to the low water solubility and poor chemical stability of active constituents of both extracts. Therefore, the aim of this study is to investigate the functionality and stability of O/W emulsions containing glabridin and carnosic acid for improving their efficiency for food application. To manufacture the O/W emulsions (10% oil, w/w), licorice and rosemary extracts were dispersed, respectively, in soy bean oil (3%, w/w) and then emulsified with various emulsifiers (decaglyceryl luarate, decaglyceryl monooleate, whey protein isolate and casein) using a high pressure homogenizer (10,000psi for 3 times). Particle size and ζ-potential of emulsions were then measured during the storage for 4weeks at room temperature. UV stability, antioxidant & antimicrobial activity were also tested. The size of oil droplets and the ζ-potential values remained within the margin of error during the 4weeks of storage. Core materials in extracts, glabridin and carnosic acid, incorporated into emulsion system were kept less damaged by UV rays than those dissolved in oil only. Antioxidant activity of emulsion systems remained significantly higher than that of oil system during storage period and also depended on the emulsifier type an increase in interfacial area in emulsion system might increase antioxidant activity of core materials dissolved in oil. The result obtained from the study could be beneficial for food industry interested in utilizing licorice and rosemary extracts.
