Carnosic acid from rosemary extract is one of the natural phenolic compounds which show the antioxidant and antimicrobial activities. Nevertheless, the use of rosemary extracts in food matrix is highly limited due to the low water solubility and poor chemical stability of active constituents of extract. Therefore, the aim of this study is to investigate the functionality and effect of starch based polymers on rosemary extract in aqueous solution for improving their efficiency of food application.
To manufacture the rosemary-starch polymer complex, starch based polymers (cycloamylose; CA, cyclodextrin; CD, hydroxypropyl-beta-cyclodextrin; HP-b-CD, maltodextrin; MD, clustered dextrin; ClusD) were firstly dispersed in 5mM phosphate buffer (pH7) according to each concentrations. Rosemary extract was then dissolved in solution to react with the polymers. Enhanced water solubility of rosemary extract was measured using a spectrophotometer. Antioxidant (ABTS assay) & antimicrobial activity (MIC test) were also tested.
In aqueous solution containing CD and HP-b-CD, the solubility of rosemary extract increased almost twice or more (189% and 248% respectively). CA, MD, and ClusD solutions also showed the results of increasing the solubility about 126%~129%. As rosemary extract dissolved better, it was also found to have increased antioxidant and antibacterial activity of rosemary-starch polymer complex. Especially, the degree of antioxidant activity has been increased much larger than the increased solubility level. Consequently, more studies are needed to determine why these results are produced. If further studies and experiments are conducted on this, it could be beneficial for food industry interested in utilizing rosemary extract.

• Shinjae Park(Dept. of Biosystems & Biomaterials Science and Engineering, College of Agriculture and Life Sciences, Seoul National University)
• Yong-Ro Kim(Dept. of Biosystems & Biomaterials Science and Engineering, College of Agriculture and Life Sciences, Seoul National University)