Extraction of surface‐active polymers from the compost of olive processing waste

Abstract

AbstractPolysaccharides and proteins with potential use as emulsifiers and thickeners are extracted at pH 5, 7, and 9 from olive processing wastes, from the onset to the end of a full compost cycle (6 months). The aim is to monitor the temporal evolution of parameters which are related to the emulsifying ability, such as surface tension, macromolecular populations distribution, and chemical composition of the produced materials. The products are characterized using size exclusion chromatography (SEC–MALLS/UV), Fourier‐transform infra‐red spectroscopy (FTIR), and equilibrium surface tension. The initial extracts comprise of a large array of macromolecules; following 2 months of composting, the polysaccharides are considerably smaller than the ones at the onset of the composting. During the subsequent months, disintegration of the olive matrix enhances the extraction. At pH 7, a variety of proteins is produced as compared to the equivalent process at pH 5, which is attributed to the charge of proteins, while parts of the cellulosic matrix and some peptidic entities are only released from the humus at the end of the composting. At pH 9 the extraction of polysaccharides is enhanced due to the charged side chains and the elimination of positive charges. These are confirmed from FTIR. The oil (miglyol)–water interfacial tension is higher at the low‐pH extracts, leaving interesting room for adjusting the emulsification capacity (favored at low pH) and the extract composition (macromolecules favored at high pH). This makes for a promising source of valuable additives from the by‐products of the olive processing industry.Practical ApplicationsIn this work, we reclaim surface‐active polysaccharides and proteins with potential use as emulsifiers and thickeners, from olive processing wastes, as these undergo a 6‐months composting cycle. The products are characterized for their composition and oil–water interface activity, a key parameter for their performance as emulsifiers. We highlight the evolution of the extracts composition and their properties as they are reclaimed at different stages of the composting process. This work can provide information on the valorization of highly polluting food processing waste as precursors of high added value food ingredients, with the relevant impact on the environment, the local economy, and the green labeling of foods.