Effect of Roasting Type on the Physicochemical Characteristics of Natural Coffee Soap Produced by Cold Process Technology

Abstract

This study investigated the physicochemical characteristics of natural coffee soap produced using the cold process method with different coffee roasting types—light, medium, and dark. The analysis focused on moisture content, pH, free fatty acids, caffeine, and free alkali levels. Results showed that moisture content ranged from 13.47% to 15.16%, pH from 10.16 to 10.67, free fatty acids from 0.79% to 1.02%, caffeine from 0.16% to 0.20%, and free alkali from 0.30% to 0.43%. Statistical analysis revealed that roasting type significantly affected moisture content, pH, free fatty acids, and caffeine levels but not free alkali content. Dark roast soap exhibited the lowest moisture content and the highest pH, indicating a firmer and more stable texture, while medium roast soap had the highest caffeine concentration. The decrease in free fatty acids with increasing roast intensity suggests enhanced lipid degradation during roasting. These findings indicate that roasting type plays a crucial role in determining the physicochemical quality of coffee-based soap. Dark-roasted coffee produced a more balanced formulation, though further optimization is needed to minimize residual alkali for safe cosmetic application