The hot–hot emulsification was used for the preparation of reference w/o emulsion (labeled as RWOE) (Table 1). The oil phase with zinc stearate was heated at 80 °C, while the aqueous phase containing dissolved magnesium sulfate was heated at 85 °C. The prepared aqueous phase was added to the prepared oil phase followed by stirring at constant temperature 5 min at 2000 rpm. Between 55 °C and 60 °C emulsions were homogenized for 3 min at 2000 rpm and then stirred at 650 rpm until room temperature was attained.