Effect of WPI/Tween 80 mixed emulsifiers on physicochemical stability of ginsenosides nanoemulsions

Abstract

Conversion of major ginsenosides into minor ginsenosides improves its pharmacological effects. This study managed to convert major ginsenosides into minor ginsenoside Rg3 and compound K (CK) by optimizing acidolysis conditions (pH, incubation temperatures and time) and evaluated the effects of the whey protein isolate (WPI)/Tween 80 ratio on the physicochemical properties of ginsenoside nanoemulsions. The optimal conditions for acidolysis are incubation at 110 °C for 3 h at a pH of 2.0, whereafter the yield of ginsenoside Rg3 and CK was 2.16 mg/g and 2.80 mg/g, respectively. For the ginsenoside nanoemulsions with 0.5% WPI as emulsifier, as Tween 80 increased from 0.1% to 0.5%, the mean droplet diameter gradually decreased from ∼740 nm to ∼310 nm. Accordingly, the encapsulation efficiency of Rg3 and CK increased by 8.36% and 9.03%, respectively, and the centrifugal stability constant increased by 49.82%. These results showed that nanoemulsion prepared with 0.5% WPI and 0.5% Tween 80 exhibited higher encapsulation efficiency and physicochemical stability. In addition, ginsenoside nanoemulsion prepared with 0.5% WPI and 0.5% Tween 80 showed great industrial applicability during freeze-thaw cycles, heat treatments and storage. Generally, the incorporation of Tween 80 as a co-emulsifier improved the encapsulation efficiency and physicochemical stability of WPI-stabilized ginsenoside nanoemulsions, which may improve its bioaccessibility, by stabilizing ginsenoside emulsions during further processing, such as during thermal pasteurization and microencapsulation.