Preparation of cosmetic emulsions
Soybean seeds (1 g per sample) were ground to
a fine powder in a mill and extracted for 48 h with
ethanol: hexane 1:1 (50 ml) solvent mixture
under sonication in an ultrasonic bath at ambient
temperature. The extract residue was removed
by filtration through layers of muslin cloth. The
extract was concentrated at rotary evaporator.
Concentrated extract was filtered through
Whatman No. 1 filter paper and was stored in
refrigerator. For the formulation oily phase
composed of paraffin oil (16 %) and emulsifier
Abil-EM90 (3 %) were heated together up to 75 ±
1 °C. At the same time distilled water (quantity
sufficient to make 100 %) was heated at the
same temperature and then 4 % soy bean
extract was added in it. Next, aqueous phase
was added to the oil phase drop by drop. Stirring
was continued at 2000 rpm by the mechanical
mixer for about 15 min until complete aqueous
phase was added, 2 to 3 drops of rose oil were
added during this stirring time to give good
fragrance to the formulation. Thereafter, the speed of the mixer was reduced
to 1000 rpm for homogenization, for a period of 5
min, and then the speed of the mixer was further
reduced to 500 rpm for 5 min for complete
homogenization; until the emulsion cooled to
room temperature. The base was also prepared
by the same method and with same ingredients
but without the soy bean seeds extract. Both
base and the test formulation were found stable
after evaluating pH, centrifugation, electrical
conductivity, phase separation, organoleptic and
physical characteristics (color, creaming and
liquefaction) and the temperature stability tests at
storage conditions of 8 ± 0.5, 25 ± 0.5, 40 ± 0.5,
and also at 40 ± 0.5 °C/70 % RH (relative
humidity) for a period of 3 months.