Robusta green coffee bean extract (Coffee canephora) contains chlorogenic acid, a polyphenolic compound that functions as an antioxidant. It acts by inactivating the oxidation reaction to prevent free radicals from forming. In this study, robusta green coffee bean extract was made in serum preparations because the serum contains a high concentration of active ingredients. It can immediately overcome skin problems and provide a relaxing effect when applied. This study aimed to determine the effect of varying the levels of extracts of robusta green coffee beans (Coffee canephora) at 2.5%, 5%, and 7.5% on the physical and chemical characteristics (organoleptic, pH, dispersibility, homogeneity and viscosity) and the physical stability in serum preparations with an HPMC 0.5% gelling agent. The study was initiated by making a serum formulation with variations in the level robusta green coffee bean extract levels of 7.5%. Organoleptic and homogeneity tests were observed. The pH, dispersibility, and viscosity tests were analyzed using the One-way Anova data analysis methods. The stability test was carried out using the Freeze-Thaw method. The results of the data before and after the stability test were analyzed using the Paired- Sample T Test. Increasing levels of robusta green coffee bean extract in serum had an effect on the results of the physical and chemical characteristics. The intensity of the color is got sharper, the spreadability increased, while the pH and viscosity decreased. The results of the Freeze-Thaw stability test during the 12 days of storage did not affect the pH value and dispersion. So, preparation was stable and safe for use on the skin.
Keywords: Robusta green coffee bean extract (Coffee canephora), serum, physicochemical characteristics, and stability.