For the preparation of emulsions, the aqueous phase
(water + thickening agents + caffeine) and the oil phase
(lipophilic compounds + emulsifiers) were heated at 70 C
and mixed together with a TurboTest (Rayneri/VMI,
Montaigu, France) at 1000 rpm. After the temperature
reached 30 C, the pH was adjusted at 5.5 with sodium
hydroxide.