Filtration-compression step as downstream process for flavonoids extraction from citrus peels: Performances and flavonoids dispersion state in the filtrate

Initiative of waste treatment has to be based on user-friendly technologies, using robust, cost-effective and low-energy consuming processes. The global objective of this study was to reduce technical steps for the extraction of flavonoids (naringin and narirutin) from citrus peel (grapefruit peel). After a first fresh peel grinding, the relevance of a simple filtration-compression, as a first downstream process, of the obtained slurry was studied. An optimization of this solid-liquid separation was proposed and the impact of a pectinolytic enzymatic treatment, resulting potentially in a larger release of flavonoids, was investigated. The results demonstrated that a preliminary step of filtration-compression, directly realized on fresh grinded peels as downstream processing for flavonoids extraction could be pertinent and that the enzymatic treatment improved the slurry filterability. An optimal separation was obtained with a transmembrane pressure of 5 bar, leading to highest extractable liquid phase volume and to an extraction around 80% of naringin and narirutin. A modelling of the filtration step, essential for the scaling of a filtration-compression process on site, was proposed. An originality of this work was to identify the dispersion state of the flavonoids within the liquid phase, capital identification for a relevant choice of the subsequent extraction step of these compounds.