The mechanism of triethanolamine (TEA) soap browning has been uncovered. The reaction proceeds as follows. Firstly, TEA is degraded into diethanolamine and acetaldehyde. Secondly, diethanolamine is further degraded into monoethanolamine and acetaldehyde. Thirdly, two molecules of acetaldehyde dimerize to crotonaldehyde, which reacts with monoethanolamine to generate brownish products with conjugated double bonds. Thus, TEA alone generates Maillard-type products through a series of degradation and recombination reactions. JAOCS 74, 891-893 (1997).Soaps are widely used in a variety of household and personalcare products. Quality soaps are triethanolamine (TEA) salts of fats or oils and create quick foaming and dense lather. Also, TEA soaps have good low-temperature solubility. However, when stored at moderately high temperatures (more than 50°C), TEA soaps have been known to acquire a brownish color. If stored for a long period, they gradually show this type of color change at lower temperatures. Colors are appealing to consumers, and discoloration damages products. In this article, we clarified the mechanism in which TEA soaps obtain a brownish color. TEA alone generates Maillard-type products (1-4) through a series of degradation and recombination reactions. EXPERIMENTAL PROCEDURESMaterials. All reagents were commercially available and were used without further purification.Qualification and quantitation of amines. A soap solution (2 mL) was mixed with 2 mL of 1M Na 2 CO 3 /NaHCO 3 buffer (pH 9), followed by addition of 100 µL of 12.5% fluorodinitrobenzene/methanol and was incubated at 50°C for 1 h. An aliquot (20 µL) was applied for reversed-phase high-performance liquid chromatography (HPLC) in a C 18 column (4.6 × 250 mm; Shiseido, Tokyo, Japan); flow rate, 1 mL/min; mobile phase, 0.01% trifluoroacetic acid with increased concentration of methanol from 0 to 80% in 30 min. The chromatographic system was equipped with an ultraviolet detector, and absorbance was read at 350 nm. The analysis was carried out at 30°C.Qualification and quantitation of aldehydes. A soap solution (1 mL) was mixed with 4 mL of 0.025% dinitrophenylhydrazine/2N HCl and was incubated for 1 h at room temperature. An aliquot (20 µL) was applied for reversed-phase HPLC as described above.Gas chromatography/mass spectrometry (GC/MS) analysis. All results were obtained with an HP 5972A gas chromatograph/mass spectrometer (Hewlett-Packard, Palo, Alto, CA). Separation of the compounds was achieved on a 15 m × 0.25 mm i.d. methylpolysiloxane (DB-1) fused-silica capillary column (film thickness 0.1 µm) from J&W Scientific (Folsom, CA). Helium was used as a carrier gas at flow rate of 0.55 mL/min. The GC injection port was maintained at 300°C, and the MS interface was maintained at 280°C. The ion source temperature was 280°C. The column oven temperature was raised from 40 to 200°C at 10°C/min and from 200 to 350°C (5 min) at 20°C/min. The mass spectrometer was operated in the scanning mode (range 40-700 m/z). Electron ionization was accomplished wit...

We have developed various kinds of ultrafine emulsifying methods using POE/POP dimethyl ether. Among ultrafine emulsions made by these methods, it was reported that an o/w type emulsion, which had been prepared with POE/POP dimethyl ether, sterol surfactant, and polar oils, was characterized by a lamellar structure on the outside of nano‐size emulsified particles (lamellar nano‐capsules). The investigation of the use of various kinds of lipophilic active ingredients inside the particles showed that the particles could hold the ingredients stably. The fluidity of emulsified particles was also investigated from the measurements of fluorescent polarization and NMR measurements. On the other hand, panel tests of a cosmetic essence containing the emulsion showed that approximately 80% of panelists confirmed the essence could improve their skin condition including skin‐moisture and skin‐tension after the treatments, and they felt a clear progress in skin‐improvement by continuing use of the essence. Keywords:  POE/POP dimethyl ether, sterol surfactant, polar oil, ultrafine emulsion, lamellar structure, lipophilic active ingredient, fluorescent polarization, cosmetic essence, skin‐moisture, skin‐tension

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