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 cos-metics 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 en-zymatic hydrolysis lignin (EHL-CM-x) were synthesized by nucleophilic substitution and applied as macromolec-ular 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 car-rier, such EHL-CM-x stabilized HIPEs enable to provide outstanding UV, thermal and oxidation protection for sen-sitive 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. (C) 2020 Elsevier B.V. All rights reserved.