Development of a coffee ground body scrub: evaluating stability and the effect of particle size

Abstract

This study aimed to develop and evaluate a sustainable body scrub formulation using coffee powder, focusing on the effect of granulometric separation on physicochemical stability and sensory performance. Two formulations were prepared using coffee powder, one with granulometric separation and one without, and were tested for pH, density, viscosity, and stability under thermal stress, centrifugation, and light exposure. All pH values remained within the acceptable range for topical application (4.58 ± 0.07 to 5.61 ± 0.13), and the scrub exhibited pseudoplastic behavior (n = 0.38), favorable for spreadability. Significant phase separation was observed under stress conditions (χ² = 8.40; p = 0.015), particularly at high temperature and light exposure, and this instability is hypothesized to be related to the thermal sensitivity of xanthan gum. Sensory analysis with 30 panelists showed high acceptability indices (AI > 70%) for all attributes. The formulation with granulometric separation (0.6–1.18 mm) showed improved sensory performance, especially in terms of odor and overall evaluation. These findings support the use of coffee powder as an eco-friendly alternative to microplastics in cosmetics, reinforcing its functional viability in stable and sensorially acceptable formulations.