The mucilage of taro showed a high EC (1,172.2 g of emulsifi ed oil per gram of protein), and this is mainly due to the presence of carbohydrates and proteins in high concentrations. According to Andrade et al. (2), the emulsifying property of the mucilage of Colocasia esculenta is related to the chemical composition, due to the presence of carbohydrates rep- resenting the hydrophilic part and the presence of proteins that are the hydrophobic part, which are part of the macro molecule AGP, which can be confi rmed in the FTIR spectrum by the presence of bands which represent AGP’s fi ngerprint. STABILITY STUDY The stability of semisolid emulsions prepared with mucilage of Col ocasia esculenta (F2, F3 e F4) and xanthan gum (F1) was evaluated by comparing pH, density, viscosity, consistency index, and fl ow behavior index (initial and fi nal) after six cycles of thermal stress (Table 3). A small reduction in the pH values was observed with the increase of the mucilage content in the formulations (Table 3). This behavior is possibly associated with the slightly acidic pH (5.91) of TM, whose content increased from formulation F2 to F4. Similarly, after the thermal stress cycles, there was also a small reduction in pH, and this is possibly related to stabilization reac- tions inherent in complex mixtures such as cosmetic creams, which are formulated with different ingredients. It should be noted that this fact did not infl uence the acceptable characteristics of the product, since the pH remained close to the pH of human skin, which is around 5.5 (31). Figure 4. Fourier transform infrared spectroscopy (FTIR) for TM. TARO MUCILAGE IN COSMETIC FORMULATIONS 287

Formulations containing both xanthan gum (F1) and TM (F2, F3, and F4) showed rela- tively close values of density, although analysis by analysis of variance and Tukey’s test showed statistically signifi cant differences. The substitution of xanthan gum by TM did not lead to intense changes in product density. This characteristic can be considered inter- esting, since the density parameter can infl uence the spreadability, and the results indi- cate little difference between the creams with TM (F1: 0.1%, F3: 0.3%, and F4: 0.5%) and the standard formulation containing xanthan gum (F1: 0.3%). The viscosity is a variable that characterizes rheologically a system and helps to determine if a product has consistency and fl uidity. The rheological evaluation is important in the study of emulsions, since it can promote information about the physical stability of a product, especially when it is subjected to temperature variations (32). The viscosity and shear rate data were adjusted to the Ostwald de Waelle model, and the consistency index (k) and fl ow behavior (n) were obtained. As can be seen in Table 3, high viscosity and consistency indices were observed both in the sample containing xanthan gum (F1: 9,624.0 mPa.s) and formulations containing TM (F2: 3,792.0 millipascal-second (mPa.s), F3: 7,752.0 mPa.s, and F4: 11,640.0 mPa.s). When using the same concentration (0.3%) of xanthan gum and TM (F1 and F3, respectively), it was demonstrated that the xan- than gum contributed to obtaining a product with a slightly higher viscosity (F1: 9,624.0 mPa.s and F3: 7,752.0 mPa.s). On the other hand, when the TM concentration was increased from 0.3% to 0.5%, there was an increase of about 21% in the value of the apparent viscosity of the product in relation to the standard formulation. In this sense, it was observed that the content of the mucilage greatly infl uences the apparent viscosity of the product. Regarding the stability test, it can be seen that the mucilage concentration also infl u- enced the rheological behavior of the samples. Whereas viscosity reduction was observed in the formulation containing xanthan gum (F1) after submission to thermal stress cycles, in contrast to formulations containing 0.1 and 0.3% (F2 and F3) of the mucilage, thermal stress led to an increase in viscosity. However, this phenomenon was not verifi ed when higher concentrations of mucilage (0.5%, F4) were used in the formulation, where Table III Properties of creams formulated with Colocasia esculenta mucilage and xanthan gum after 24 h (initial time) of preparation and after the six cycles (12 d of thermal stress) Sample Time pH Density η (mPas.s) γ (s-1) k (mPa.sn) n F1 24 h 6.92g ± 0.01 0.979e ± 0.007 9,624.0 0.24 3,193.31 0.22 12 d 6.80h ± 0.05 0.989e ± 0.003 7,152.0 0.24 2,441.17 0.24 F2 24 h 7.03a ± 0.06 0.930a ± 0.008 3,792.0 0.39 2,735.73 0.65 12 d 6.73b ± 0.11 0.972b ± 0.002 10,920.0 0.39 7,243.77 0.56 F3 24 h 6.84c ± 0.01 0.920c ± 0.006 7,752.0 0.34 3,984.25 0.38 12 d 6.68d ± 0.01 0.923c ± 0.003 8,520.0 0.34 5,089.15 0.52 F4 24 h 6.78e ± 0.01 0.915d ± 0.006 11,640.0 0.12 2,818.34 0.34 12 d 6.68f ± 0.03 0.928d ± 0.054 5,184.0 0.12 2,443.54 0.65 #F1: control formulation using 0.3% xanthan gum. *F2: 0.1% mucilage. *F3: 0.3% mucilage. *F4: 0.5% mucilage. *Equal letters in the same column do not have signifi cant differences according to the Tukey test (p 0.05). η: apparent viscosity millipascal-second (mPa.s) γ: shear rate (s-1) k: consistency index n: fl ow behavior index. JOURNAL OF COSMETIC SCIENCE 288