Stability of vitamin A in oil-in-water-in-oil-type multiple emulsions

The stability of vitamin A was studied in three different emulsions: oil-in -water (O/W), water-in-oil (W/O), and oil-in-water-in-oil (O/W/O). The stab ility of retinol (vitamin A alcohol) in the O/W/O emulsion was the highest among the three types of emulsions; remaining percentages at 50 degrees C a fter 4 wk in the O/W/O, W/O, and O/W emulsions were 56.9, 45.7, and 32.3, r espectively. With increasing peroxide value of O/W and W/O emulsifiers, the remaining percentage of vitamin A palmitate and retinol in the emulsions d ecreased significantly, indicating that peroxides in the formulae accelerat e the decomposition of vitamin A. Organophilic clay mineral tan oil gelling agent and a W/O emulsifier) also affected the stability of retinol; synthe sized saponite was better than naturally occurring bentonite for retinol st ability. The stability of retinol in the O/W/O emulsion increased with incr easing inner oil phase ratio (phi(i)), whereas in O/W it was unaffected by phi(i). Encapsulation percentage of retinol in the O/W/O emulsion, the rati o of retinol in the inner oil phase to the total amount in the emulsion, in creased with increasing phi(i). The remaining percentage of retinol in the O/W/O emulsion was in excellent agreement with encapsulation percentage, su ggesting that retinol in the inner oil phase is more stable than that in th e outer oil phase. Addition of antioxidants (tert-butylhydroxytoluene, sodi um ascorbate, and EDTA) to the O/W/O emulsion improved the stability of ret inol up to 77.1% at 50 degrees C after 4 wk. We conclude that the O/W/O emu lsion is a useful formula to stabilize vitamin A.