The textural properties of the skin moisturizer samples were measured
using a Texture Analyzer TA.XT Plus (Stable Micro Systems Ltd.,
Godalming, U.K.). The unit had a load cell of 30 kg, with an A/BE back
extrusion rig, which included a locating base plate, sample containers
(50mm internal diameter), and compression discs (35mm diameter). After
penetrating the sample (25 mm deep) at a rate of 2.0 mm/s, the probe
returned to the initial position. Following this procedure, the
firmness, consistency (related to hardness), cohesiveness, and index of
viscosity (related to adhesiveness) of the samples were measured in
duplicate and average values were calculated for all parameters (all
expressed as positive values). All the measurements were taken at room
temperature of 20 ± 0.2°C.
Microscopy: Emulsions were observed using a portable microscope
Dino-Lite® Edge AM7515MT8A (Taipei, Taiwan), with a magnification of
900x, and images were captured with the in-built camera 5Mpixels
(2592x1944). For this, a small amount of sample was mounted on a glass
slide along with a drop of distilled water under a coverslip. All
samples were examined two months after preparation to assure long term
stability.
Evaluation of white residues after product application on skin: An adaptation to the descriptive skin-feel analysis method described by
ASTM E1490-0365 was implemented here to establish a
qualitative comparison of the white residues left by two products during
rub-out. In this case, 0.1 g of each product was spread on the
mid-section of the forearm, using the index finger for one product and
the middle finger for the other product, both from the opposite hand.
The white residues of both samples were compared after 15 circular rubs
at a rate of two strokes per second.