Synopsis

Human sebum is a mixture of triglycerides, fatty acids, wax esters, squalene, cholesterol, and cholesterol esters. P. acnes, a bacterium that is normally found on the skin, hydrolyzes certain triglycerides to fatty acids, thereby changing the sebum composition. The objective of this study was to examine the physical state of a model sebum and the effect of variations in its composition on its physical properties including (a) the carbon chain length of the components, (b) the ratio of unsaturated to saturated components, and (c) the ratio of triglycerides to fatty acids. A model sebum mixture was prepared based on a composition reported in the literature and evaluated by differential scanning calorimetry (DSC). Since cholesterol and cholesterol esters contribute insignificantly to sebum composition, they were not included. Squalene was kept constant (13%), while the concentration of the rest of the components was varied. Variations of sebum were prepared by dissolving all components in a 3:1 chloroform-methanol mixture for uniformity. Subsequently the solvent was evaporated at room temperature. The samples were then analyzed using DSC. Four distinc