mucilage was suspended in 100 mL water and 100 mL soybean oil, and homogenized at 8,000 rpm in an extract dispenser (Q252-28, Quimis) for 1 min. The mixture was then separated into four tubes of 50 mL, each containing 30 mL of emulsion and immediately centrifuged at 4,000 rpm for 5 min. The EA was calculated by the ratio between the volume of the emulsifi ed layer and the total volume in the tube, according to equation 2: Volume of the emulsified layer(mL) EA = ×100 Total volume in the tube(mL) (2) To evaluate the emuls ion sta bility, an emulsion was prepared according to the procedure described earlier, heated in a water bath at 80°C for 30 min, and cooled in tap water for 15 min. The emulsion was then centrifuged for 5 min at 4,000 rpm in a centrifuge (Sorvall ST16R, ThermoFisher Scientifi c). The emulsion stability (ES) was calculated as the ratio between the volume of the remaining emulsifi ed layer and the total volume in the tube, according to equation 3. Volume of the remaining emulsified layer(mL) ES= ×100 Total volume in the tube(mL) (3) DEVELOPMENT OF COSMETIC FOR MUL ATIONS Four cosmetic formulations wer e developed using the ingredients described in Table 1. A volume of 1,000 mL of each cream formulation was prepared by heating the ingredients of the oil phase (Phase A: 90 g) and the aqueous phase (Phase B: 3 g in F1 and F3 1 g in F2 and 5 g in F4 dispersed in approximately 800 mL of water) separately, to a tempera- ture of 75° ± 5°C. Phase B was poured into Phase A under constant stirring (600 rpm) to avoid blistering using a mechanical stirrer (TE 139). Stirring was continued until the emulsion temperature reached 40°C and then added to Phase C (Phase C: 10 g of the solid Table I Cosmetic formulations Ingredients Concentration (% w/w) # F1 F2 F3 F4 Phase A: oily Glyceryl monostearate 3 3 3 3 Cetearyl alcohol 3 3 3 3 Helianthus annuus seed oil 1 1 1 1 Cocos nucifera oil 2 2 2 2 Phase B: watery TM - 0.1* 0.3* 0.5* Xanthan gum 0.3 - - - Distilled water q.s. q.s. q.s. q.s. Phase C Sodium benzoate 0.5 0.5 0.5 0.5 Caprilyl glycol 0.5 0.5 0.5 0.5 Distilled water q.s. q.s. q.s. q.s. # F1: control formulation using 0.3% xanthan gum, *F2: formulation using 0.1% mucilage, *F3: 0.3% mucilage, and *F4: 0.5% mucilage, q.s.: quantum satis/quantum suffi cit. JOURNAL OF COSMETIC SCIENCE 282

ingredients solubilized in approximately 200 mL). The emulsion containing all ingredi- ents was constantly stirred until it reached room temperature, and then distilled water was added to reach the fi nal volume. The formulations developed remained standing for 24 h for stabilization before starting the characterization tests. FORMULATION STABILITY UNDER STRESS CONDITIONS Twenty-four hours after preparation , the samples were conditioned in transparent glass vials with 2/3 of their capacity, with sealed caps, to avoid the loss of gases and steam to the medium, and subjected to cycles of thermal stress: 24 h at 45°C and 24 h at 5°C for 12 d, totaling six complete cycles. The samples were analyzed after prepa ration and at the end of each thermal stress cycle. The physical–chemical analyzes performed in each sample were pH, density, viscosity, and rheological parameter evaluation. The pH was measured using a benchtop pH meter (Q400AS, Quimis), previously calibrated with buffer solutions, and the pH measurements were taken directly on the samples. The density evaluation was performed with the aid of a stainless steel pycnometer, which is recommended for semisolid products. The calculation for relative density determination was performed through equation 4: 2 1 0 – = – M M0 d M M , (4) where d = density, M0 = mass of the em pty pycnometer (g), M1 = mass of the pycnometer with distilled water (g), and M2 = mass of the pycnometer with the sample (g). The apparent viscosity of formulations was measured using a Microprocessor Rotary Viscom- eter (Q860M21, Quimis) with a spindle 3. The temperature of the samples was maintained at 20° ± 1°C with the aid of a thermostated bath. The fl ow curves were obtained by measuring the viscosity (η) in mPa.s and increasing shear rates (γ) of 0.1–1 s-1. The rheological parame- ters were adjusted to the Ostwald De Waele model (potency law), and the values of consistency index (k) and fl ow behavior index (n) were obtained by equation 5. τ = shear stress. = I k( ƣ)n–1. (5) The data of characterization parameters of t he formulations were submitted to analysis of variance and Tukey’s test [(signifi cance of 95%) (p 0.05) XLSTAT Software (version 2018 Free, Microsoft Excel, Addinsoft, Paris, France)]. RESULTS AND DISCUSSIONS CHARACTERIZATION OF TAR O MUCILAGE (TM) X-ray di ffractometry. The X-ray diffractog ram of TM (Figure 1) s hows that the mucilage of the rhizomes of Colo- casia esculenta (L.) Schott presents a semicrystalline profi le, which is a characteristic of many TARO MUCILAGE IN COSMETIC FORMULATIONS 283