From waste to valuable cosmetic raw material: the valorization of coffee silverskin following the approach of circular economy

Coffee silverskin (CS) is a tegument of coffee beans that constitutes a by-product of the roasting process. CS has no commercial value and is currently discarded as a solid waste. CS chemical composition can be broken up into cellulose, lignin, proteins, lipids and phenolic compounds, each of which has a great potentiality as a raw material in many fields, included cosmetics. The aim of the work is to selectively extract the lipid and the phenolic fractions from CS and to study their use as functional and active ingredients in cosmetic formulations. This project is part of a bigger program named CirCo (Circular Coffee), focused on the valorization of this residue of agro-food industry, not only in cosmetics, but also for innovative and sustainable solutions in paper production. CirCo involves different academic and industrial research groups and aims at creating a model that embraces the increasingly emerging circular economy approach, practicing industrial symbiosis, waste-to-resource vision and life cycle thinking. CS extracts are obtained using supercritical fluid extraction (SFE), obtaining a promising lipid fraction. The compound is a semisolid brownish material and shows a peculiar composition of fatty acids, with a significant amount of C20:0 and C22:0. The organoleptic and the chemico-physical properties of the resulting lipid fraction are firstly assessed. Its chemical composition is determined by means of fatty acid and unsaponifiable matter analyses. Volatile content analysis, FT-IR, DSC and GPC are used to acquire further technical data. Chemico-physical characterization is targeted on one side to assess the safety and the regulatory compliance, on the other side to classify the lipid fraction in terms of cosmetic properties. A stability study is then performed on the raw material to define its oxidation stability and shelf life, while compatibilities with other ingredients are carried out to guide the formulation. Based on the results obtained, the most suitable formulations are selected to generate prototypal make-up products using the lipid fraction of silverskin. The underway scale-up of the extraction from lab to pilot scale confirms the extraction protocol and guarantees the needed amount of materials for formulating new cosmetic products. The choice to valorize a residue of agro-food industry for different applications, the adoption of a promising and green process such as SFE, the network created among reaserch groups of academia and industry are virtuous elements useful to explore how far we are from a complete sustainable industrial development, where environment, business, quality and safety standards need to fit the same big picture