The Advantages of Palm‐Based Dihydroxy Stearate in Deodorant Sticks

Dihydroxystearic acid (DHSA) has been prepared from palm oleic acid via catalytic reaction. An in vivo test confirmed that the use of DHSA at 5% and below is nonirritating. With two vicinal alcohol groups positioned at C9 and C10, DHSA has been found to be applicable in cosmetics as thickeners or gelling agents. Stearic acid is known to be used as a stick‐gel foaming agent. The aim of this study was to examine the possibility of combining the potential stick‐forming properties of DHSA with antimicrobial properties, and at the same time to determine its key physical properties and the deodorant efficacy of this raw material. A ternary phase diagram of palm‐based dihydroxystearic acid (DHSA)/propylene glycol (PG)/sodium hydroxide was constructed at 80°C. The phase changes were observed visually through polarizer film and a polarizer microscope. The result showed that the anisotropic properties changed from isotropic, lamellar liquid crystals identified as Maltese cross patterns and 2‐phases. Deodorant sticks developed based on the Maltese cross pattern showed the most stable network. Formulae D4 (antimicrobial active and perfume), D5 (antimicrobial active), D6 (perfume), and D7 (without antimicrobial and perfume) were compared with C1 and C2, commercially available sodium stearate‐based deodorant sticks. The sticks were characterized for pH, softening point, hardness, disintegration time, syneriesis upon three months' storage and in vivo microbial test. The physicochemical properties remain unchanged after three months' storage. The screening for bacteria type was made using blood agar media and the species identified was Staphyloccocus. In manittol agar and saboroud media, it inhibited the bacteria and fungus/yeast growth for at least four to eight hours in D7. The same results were found with the rest of the samples.

Keywords:

• Dihydroxystearic acid
• deodorant stick
• stearic acid
• ternary system
• antimicrobial properties

Acknowledgments

I would like to thank Y Bhg. Tan Sri Datuk Dr. Yusof Basiron (Director‐General of MPOB) for giving the opportunity to publish this article. Special thanks to Dr. Salmiah Ahmad for her guidance and contribution towards the completion of this project. Thanks also to Hajar Bilal and Aishah Tahir for their assistance.