Limnophila aromatica Crude Extracts as Natural Emulsifiers for Formation and Stabilizing of Oil-in-Water (O/W) Emulsions

Abstract

This study mainly focused on the emulsifying performance of Limnophila aromatica crude extracts obtained by using different ethanolic aqueous solutions (0, 25, 50, 75, and 99.5% (v/v)). All Limnophila aromatica extracts (LAEs) were able to produce emulsions with a volume mean droplet diameter (d4,3) ranging from 273 to 747 nm, except for LAE-99.5 (3269 nm). Only the emulsion prepared by LAE-75 was stable during seven days of storage, without significantly changing droplet size (479–495 nm). The result showed that all LAEs could reduce interfacial tension varied within 12.5 and 16.1 mN/m at the soybean oil/extracts (1% w/w) interface. Compared to other extracts, LAE-75 did not contain the highest protein, saponin, and phenol content (4.36%, 20.14%, and 11.68%, respectively), but it had the lowest ash content (14.74%). These results indicated that the emulsifying performance of LAEs did not rely only on interfacial tension and/or surface-active compounds. The residual demulsifiers, such as inorganic substances, were also significantly involved in the emulsions’ destabilization. Finally, the emulsion consisting of 0.5% (w/w) LAE-75 and 5% (w/w) soybean oil showed considerable stability during storage up to 30 days at different temperatures (5 or 25°C). Therefore, Limnophila aromatica extract has a potential application as a new source of natural emulsifier.