The growing interest in natural and sustainable ingredients is driving innovation in the field of cosmetics. In this context, the utilisation of coffee grounds and orange peels as post-consumption waste under the principles of the circular economy not only fosters environmental sustainability but also economic sustainability. The soap formula incorporated 2% coffee grounds, brewed coffee extract, and orange peel essential oil, and was produced using the hot process method. The pH of the soap was measured in three separate samples, yielding values of 8.93, 9.06, and 8.96, with a mean of 8.98 ± 0.07, indicating its suitability for topical application. The gas chromatography-mass spectrometry (GC-MS) analysis of the pure orange peel essential oil identified dl-limonene (89.0%), α-myrcene (2.0%), and α-pinene (1.0%) as the dominant compounds. In the soap matrix, these compounds were retained at 93.3%, 120.0%, and 85.0%, respectively, indicating moderate thermal loss with occasional variance. Fatty acid profiling revealed oleic acid (41.2%), stearic acid (22.5%), and palmitic acid (13.7%), which contribute to moisturization, lathering, and hardness. The findings support the integration of food-derived waste materials as functional ingredients in cosmetic formulations, enhancing both ecological value and product efficacy.
Büyükyörük et al. (Thu,) studied this question.