COSMETIC CREAM WITH AQUEOUS EXTRACT AND DATE FRUIT SEED OIL 365 Figure 3. (A) Henry’s straight, (B) iso-response surface, and (C) response surface. Case of viscosity (Vis) (Pa·s).

JOURNAL OF COSMETIC SCIENCE 366 The quadratic equations are in the form: Spreadability: YSp = 13.99 X1 + 18.59 X2 + 8.89 X3 − 17.36 X1X2 + 2.01 X1X3 + 3.06 X2X3 − 123.87 X1X2X3 Viscosity: YVis = 17.23 X1 + 33.81 X2 + 17.23 X3 + 37.53 X1X2 + 43.82 X1X3 + 3.28 X2X3 + 107.18 X1X2X3 The calculated model values in the center of the domain (Sp = 7.87 and Vis = 34.90) are close to those found experimentally (Table I). The response surface and contour curves related to the Sp are illustrated in Figure 2B and C, respectively. As that can be seen, the Sp values are positively correlated with proportions of both aque- ous and fatty phases, the beeswax proportion being fi xed at its mean value. Compared with the Sp, the Vis shows another behavior (Figure 3B and C). The high values were obtained in the area close to the center of the experimental domain, and at low values of beeswax fractions. Globally, results show that there is a relatively wide composition range to obtain a suit- able cosmetic cream from the point of view of Sp and Vis, knowing that for a moistur- izing cream, the values of these two criteria are required to be 15 and 19 cm2 and 7.16−88.00 Pa·s, respectively (33). Taking into account these data, the formulation corresponding to the test 2 (Table I) seems to be the most appropriate, involving a fi nal product with an acceptable white external aspect and a homogenous viscous texture (Figure 4). Figure 4. Cosmetic cream sample of the selected formulation.