High internal phase emulsions stabilized with carboxymethylated lignin for encapsulation and protection of environmental sensitive natural extract.

Oil-in-water (O/W) high internal phase emulsions (HIPEs) are widely used in foods, pharmaceuticals and cosmetics due to the high drug loading ratio, specific rheological behaviors and long shelf life. However, protective performance of active components within HIPEs maintains a low level. Herein, a series of carboxymethylated enzymatic hydrolysis lignin (EHL-CM-x) were synthesized by nucleophilic substitution and applied as macromolecular surfactant to stabilize the O/W HIPEs. It was found that EHL-CM-x combined with a small dosage of alkyl polyglycoside (APG) are able to stabilize HIPEs with 87 vol% soybean oil under neutral condition, which could be recognized as the highest internal phase reported in foods and pharmaceuticals. As a bioactive compound carrier, such EHL-CM-x stabilized HIPEs enable to provide outstanding UV, thermal and oxidation protection for sensitive natural extracts. The residual drug level obtained in this work is more than two times other gliadin/chitosan hybrid particles and sulfomethylated lignin stabilized HIPEs after UV irradiation. In vitro experiments showed that the minimum inhibitory concentration of curcumin within HIPEs against S. aureus and E. coli was 3.13 mg/mL and 12.5 mg/mL, respectively. Such lignin stabilized HIPEs could be potentially used in various areas, especially those with high stability and biosafety requirements.