RICESORB® FOR LOOSE FACE POWDERS 295 using naked eye and a colorimetric examination, bulk density, fl ow property (angle of repose), and pH according to the previously mentioned methods. In addition, the specifi c assessment of the fi nished products, loose face powders, based on TIS 443-2525 (11) was performed as mentioned following paragraphs. TESTING OF MOISTURE The te sting procedure was modifi ed from t he method of TIS 443-2525 (11). Moisture present in loose face powder formulations was determined using an HB43-S Moisture analyzer equipped with a built-in balance (Mettler Toledo Co. Ltd.). An empty alumi- num sample pan (Mettler Toledo Co. Ltd.) was placed in a sample pan handler of the moisture analyzer. After taring, a sample (3 g) was accurately weighed on the sample pan. The drying and measuring processes were carried out at 105 ± 2°C. The percent- age of the moisture content (%MC) of the sample was automatically achieved using the analyzer. TESTING OF INSOLUBLE SUBSTANCES IN BOILING WATER The sample (1 g) was accurately weighed, tr ansferred into a 500-ml beaker, and wetted with ethanol. Then, 200 ml of distilled water was added to the sample and boiled. After sedimentation, a clear water portion of the mixture was fi ltered through a Gooch crucible, a sintered glass fi lter or a porous porcelain. The fi lter equipment was accurately weighed before the fi ltration process. The remaining sample in the beaker was rinsed with distilled water and subjected to fi lter. The obtained fi ltrate was dried in a hot air oven (ED400/ E2-N, Scientifi c Promotion Co. Ltd., Bangkok, Thailand) at 105 ± 2°C until a constant weight was obtained. The percentage of insoluble substances in boiling water was calcu- lated based on the following equation: weight of filtrate g % insoluble substances in boiling water weight of test sample g  ¬ ž ­q100. ž ­ Ÿ (3) STABILITY OF LOOSE FACE POWDERS The stab ili ty of loose face powders was monito red by storing the samples at 45 ± 2°C (RH = 75% ± 5%) and ambient temperature for 2 mo (12). The changes in physicochemical properties (e.g., color, odor, moisture, and pH) of the samples were recorded after the end of each month. All experiments were performed in triplicate. STATISTICAL ANALYSIS Student’s t-test and one-way analysis of variance were used to test the statistical differ- ence, and a p-value of 0.05 was considered signifi cant difference.
JOURNAL OF COSMETIC SCIENCE 296 RESULTS AND DISCUSSION PHYSICOCHEMICAL PROPERTY O F RICESORB® AND TALCUM Morphology. Using the SEM technique, it was found that RiceSo rb® had almost a spherical shape with rather smooth surface morphology. Uniformity of particles was observed. Its particle size was around 6 μm (Figure 1). Talcum possessed irregular surfaces and bigger particle sizes about 25 μm. It was observed that the particle sizes of talcum were not uni- form. Talcum used in the current study was pharmaceutical grade its greater particle sizes thus provided lower surface areas for sebum or oil absorption in comparison to RiceSorb®. Also, more spherical shapes of RiceSorb® could improve the skin feel (1). Bulk density, fl ow property, and pH. As seen from Table II, bulk densities of RiceSorb® and talcum were 0.40 ± 0.01 and 0.55 ± 0.11 g/ml, respectively. The bulk density of the two materials differed signifi cantly (p 0.05). It was noted that RiceSorb®, which had almost spherical shapes and smaller particle sizes, exhibited lower bulk density than talcum. The fl ow of powder is essential for the manufacturing process, especially during mixing and packaging. The fl ow characteristics of the substances were determined by angle of repose measurement. Several methods have been proposed for angle of repose determination such as the tilting box method, fi xed funnel method, and hollow cylinder method (13). In the current study, the fi xed funnel method was selected. It was found that the angle of repose of RiceSorb® was lower than that of talcum (Table II). Based on the USP 41 and NF 36 (10), RiceSorb® with an angle of repose of 35° could be classifi ed as having good fl owability, whereas talcum, which had an angle of 38°, could be classify as fair (aid not needed) fl owability. This is probably due to rather rounded shape and smooth surface of RiceSorb®. Such properties are capable of reducing resistance to movement between par- ticles, resulting in a lower angle of repose. The pH values of two materials were markedly different. Talcum had a higher basic pH of 8.8. RiceSorb® showed a weak acidic pH of 6.2, which is more compatible with the skin surface pH. Based on these results, the basic properties of RiceSorb® were more promising than those of talcum. LOOSE FACE POWDERS: PHYSICOCHEMICAL PROPERTY AND STABILITY The ing redients of loose face powders composed of RiceSorb® or tal cum, other white mate- rials such as zinc oxide and zinc stearate, tamarind fruit pulp extract, and preservatives. Five formulations of loose face powders were prepared, namely, FT0, FT1, FT2, FT3, and FT4 based on the ratios of talcum and RiceSorb® (4:0, 3:1, 2:2, 1:3, and 0:4). The physicochemical properties of the freshly prepared formulations (24 h) were investigated Table II Bulk Density, Angle of Repose, and pH of RiceSorb® and Talcum Substance Bulk density (g/ml) Angle of repose (°) pH [mean ± standard deviation (SD), n = 3] RiceSorb® 0.40 ± 0.01 35.10 ± 1.27 6.16 ± 0.01 Talcum 0.55 ± 0.11 38.07 ± 0.44 8.75 ± 0.01 n: number of samples.
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