SENSORY ANALYSIS OF A CHITOSAN GEL NANOFORMULATION 305 The consistence indexes obtained for the formulations, through the Ostwald fl ow model, were 12.28 ± 1.45 (CH), 17.19 ± 0.55 (CH-NC), 13.93 ± 0.32 (HEC), 17.27 ± 0.18 Figure 2. Transmission electron photomicrographs of formulations. (A) NC in aqueous suspension 200.000×, (B) NC in aqueous suspension 500,000×, (C) CH-NC 200,000×, (D) CH-NC 500,000×, (E) HEC-NC 200,000×, (F) HEC-NC 500,000×, (G) CH-OPT 200,000×, and (H) CH-OPT 500,000× (CH: chitosan gel, HEC: hydroxyethyl cellulose gel, NC: nanocapsules, OPT: optimized gel) Size bars to the left corresponds to 100nm, while size bars to the right corresponds to 50nm.

JOURNAL OF COSMETIC SCIENCE 306 (HEC-NC), 14.84 ± 2.74 (CH-OPT), 19.70 ± 1.02 (CH-NC-OPT). All hydrogels showed similar consistence values, although the hydrogels containing nanocapsules pre- sented signifi cant slightly higher values than the respective hydrogels containing pure water (p 0.05). Comparing the different hydrogels containing water (CH, HEC, CH- OPT), no differences were found but, on the other way, comparing the different hydrogels containing nanocapsules (CH-NC, HEC-NC, CH-NC-OPT), the CH-NC-OPT pre- sented signifi cant slightly higher consistence (p 0.05), maybe due to an interaction of the nanocapsules and the adjuvants, increasing the consistence. The rheological proper- ties are important to be determined since there might be a relation between them and the sensory properties (25). SENSORY ANALYSIS Phase I: Chitosan gels versus hydroxyethyl cellulose gels. The phase I sensory analysis comprised the comparison between the chitosan gel and a hydrogel commonly used in cutaneous formulations (hydroxyethyl cellulose gel) and also, between the chitosan hydrogel con- taining and not containing nanocapsules. Table II shows the responses from the volun- teers, in percentages, when comparing the paired samples. It is interesting to notice that the percentage of volunteers who saw differences between samples was always higher than the percentage of volunteers who thought the samples were similar for the present attri- bute. Nevertheless, it was important to determine if the percentage of volunteers who pointed out that there were differences among samples were signifi cantly higher than the volunteers who pointed out no differences were perceptible. When this requirement was achieved, the answers of the volunteers who choose one or other sample for the evaluated attributes were taken into account and another statistical test was performed only consid- ering these volunteers. Table III shows the p value obtained comparing the percentage of volunteers who saw differences among samples with the percentage of volunteers who could not see differ- ences. For the attributes oiliness (comparison CH vs. CH-NC), immediate stickiness (all comparisons), fi lm formation (all comparisons), homogeneity of the fi lm (comparisons CH vs. HEC and CH vs. CH-NC), and preference (all comparisons), the percentage of volunteers who choose one or the other sample was signifi cantly higher than the Figure 3. Rheological profi les of formulations (shear stress vs. shear rate) (CH: chitosan gel, HEC: hydroxy- ethyl cellulose gel, NC: nanocapsules, OPT: optimized gel).