Physicochemical characteristics of Enteromorpha prolifera Extract as a Functional Food Additive

Abstract

Enteromorpha prolifera is a common species among the green algae found all over the globe. Physicochemical characteristics and biological activity of integral, hydrolyzed or fractionated extract of E.prolifera has been widely tested in vitro and in vivo, but not many of the researches had been focused on whether the extract maintains its various functionality in the applied food system. This study aims to analyze E.prolifera extract (EPE) as a supplement in food system carrying retinol. To evaluate the physicochemical characteristics of EPE, chemical composition was investigated prior to any other measurements. The extracts had a yield of 13.47% (g extract/g depigmented raw material), 47% of polysaccharide content, and other minor components consists of 12.4% protein and 19% sulfate attached to the building blocks of polysaccharides. Rheological characteristics depending on temperature and pH of the extract was assessed. EPE did not form gel in low concentrations below 2.5% as well as in strong acidic environment of pH lower than 3.5. The strongest gel was formulated in pH 7 with equilibrated G value around 800 Pa (pH 5: 79.38 Pa, pH 9: 480 Pa). EPE gels melted as the temperature rose, and restored the original network as the temperature reached 4 ℃ again. A model food system, O/W emulsion (formulated with synthetic emulsifier Tween 20 and protein emulsifier WPI), was fortified with EPE to investigate the effect of the extract as a protective material against instability factors. Addition of over 5% resulted in a gel, which was also thermo-reversible. Emulsions did not set to gel with EPE concentration below 2.5%. In emulsions formulated with neutral buffer, addition of EPE did not affect the emulsion stability nor the retinol retention rate after 6 days of storage (p>0.05) up to this concentration except for the synergistic increase in gel strength. On the contrary, reactions in emulsions prepared with pH 3.5 buffer were more diverse. The addition of EPE in acidic Tween 20 emulsion enhanced retinol stability depending on the amount of EPE dissolved (Blank: 58.16±4.7%, EPE 2.5%: 81.81±6.8%). For WPI emulsions, excessive use of EPE caused undesirable interaction between protein emulsifier and polysaccharide, resulting in retention rate (22.91±4.3%) lower than that of the blank (40.33±6.5%). The optimum concentration of EPE within the studied conditions was 0.5% (77.16±6.8%). These results suggest a possibility of E.prolifera utilization as a new additive in food system, having desirable rheological properties that leads to a stabilized emulsion in optimum concentration range. It is also a staple species of green algae around the world, and its physiological benefits have already been through in-depth researches. Moreover, the functional fraction of E.prolifera can be extracted without harsh or expensive chemical treatments, and is generally regarded as safe (GRAS) food material. These functionalities suggests that EPE can be applied to the food system as a universal, multifunctioning stabilizing supplement as well as a drug transport supporter.