Different strategies are studied to incorporate lipid-soluble bioactive molecules into water-based food systems. However, these systems solely cannot protect the core compound through the storage period, especially when the core is exposed to environmental stress factors. Water soluble fraction of the crude extract from Enteromorpha prolifera was analyzed for its physicochemical characteristics including chemical composition, structure, rheological and thermal properties. The extract was added to O/W emulsion system containing retinol and stabilized with Tween 20, WPI and sodium caseinate to improve storage stability through different modes of action; as a chelator of metal ions and as a scavenger of radicals. Storage stability was mainly determined by zeta potential, particle size distribution, and retinol retention.
The water-soluble extract of E.prolifera mainly consisted of anionic polysaccharide, while impurities of protein, mineral and other pigments were present. Mode of action analysis showed that the extracts had both ferrous ion chelating ability(EC50=0.67%) and free radical scavenging ability(EC50=0.23%), indicating a multifunctioning mechanism of the heterogeneous extract. Addition of extract (0.1%~1% in total emulsion) did not affect the physical stability during 1 week storage.
Protective materials are often added to food systems to improve the stability of core materials but excessive use of additives may be repulsive to consumers. In contrast, the optimum concentration range of E.prolifera extract is much lower compared to that of conventional usage of other materials and has lower toxicity to that of strong chelators while providing effective protection.

• Sun-Young Park(Center for Food and Bioconvergence, Department of Biosystems and Biomaterials Science and Engineering, Seoul National University, Seoul, Republic of Korea)
• Yong-Ro Kim(Center for Food and Bioconvergence, Department of Biosystems and Biomaterials Science and Engineering, Seoul National University, Seoul, Republic of Korea)