Preliminary evaluation of pressurized hot water extraction for the solubilization of valuable components from hospital kitchen wastes

Abstract

An alternative to mitigate the environmental impact of food waste is the separation of valuable components. Due to the difficulty and heterogeneity of such wastes, the study of model systems allowing a regular and predictable production and composition was used. A mixture of pre- and post-consumption kitchen wastes from a hospital with an automated organic matter segregation and drying system (HKW) has been collected to obtain representative samples of the different diets prepared daily. The chemical characterization of streams revealed a variation in composition of the wastes depending on the menus. Those from dinner + breakfast (D + B) presented protein content in the range 42–54% of the dry weight and those form lunch + snack (L + S) in the range 19–33%, whereas the carbohydrate content was 52–65% in D + B and 47–53% in L + S waste streams. These values suggested the possibility of proposing a different valorization scheme for each type of stream. In this study, a green extraction process with pressurized hot water under microwave heating has been explored for the solubilization of the most abundant and valuable components, protein, and carbohydrates. The starch fractions recovered from the crude extract were proposed for the formulation of anti-freezing hydrogels suitable for 3D printing, and the possibilities of valorizing other fractions such as proteins as plant biostimulants are also discussed.