Advanced characterization of sustainable exfoliating particles from food waste for facial scrub formulations and their in vivo evaluation

Public opinion is increasingly interested in environmental issues and the state of health of the planet. As the economic system continues to go through a process of continual change, the most important problem is to plan for a sustainable future. This research presents a well-defined experimental strategy for converting food waste into cosmetic products, particularly face scrub formulations, by employing, whenever possible, ingredients from natural sources. Food and agricultural waste, such as coffee grounds (CF), malt residue (TM), hop remnants (HS), pomegranate leftovers (WF and MF), and pomace (WP and WL), were used in this work as source products for creating mechanical cosmetic scrubbing. The samples were subjected to drying, grinding, and sieving to generate powders with varying grain sizes showing particles with diameters between 420 and 707 μm for CF, TM, WL, HS, and WF samples and 1000 μm for MF and WP samples. An optical microscope study determined every sieved fraction's size, shape, and surface properties. Following the assessment of powder wettability, the chosen samples were used as green exfoliating particles (GEP) to formulate lipogel-based facial scrubs. The lipogels were characterised by their physicochemical properties, microbial stability and in vivo efficacy. For all the formulations, a marked reduction in the sebum was observed at t30, which was only partially restored at t60. Results in the transepidermal water loss (TEWL) among all the formulations and at different time points confirmed that the skin barrier integrity is not affected by mechanical exfoliation, also encountering the volunteers' appreciation.