Résumé
Grapes are the world's second largest produced fruit crop, with an annual production of 77 million tons in 2013 [1]. Among grapes processing industries, wineries induce approximately 10 million tons of byproducts per year, mostly pomace and lees [2]. Nowadays, the management and the valorization of food industry wastes constitute an economical, environmental and social challenge. It turns out that grape based products such as grape pomace contain a high amount of polyphenols, well known for their biological activities [3]. Thus, the extraction and purification of those high added value compounds from grape pomace are of great interest for cosmetic, nutraceutical and other chemical industries. Membrane technologies, well-known for their several advantages (low environmental impact, no solvent utilization, high selectivity, etc.), can be used to recover different classes of phenolic compounds from pomace extract, according to their molecular weights. In food industries, crossflow filtration is generally performed using tubular mineral membranes under high crossflow velocities [4, 5]. However, immersed organic hollow-fiber membrane process could be interestingly used as an alternative separation technique for such application, notably due to the significant reduction of the energy consumption [6]. In this context, the aim of this work was to provide reliable information to develop a convenient immersed hollow-fiber membranes pilot for the isolation of polyphenols from grape pomace extracts. Therefore, lab-scale experiments were performed using a frontal filtration module in order to identify the main parameters governing the separation efficiency. Three factors known to impact membrane performances were considered and tested: (i) the membrane average pores diameter or molecular weight cut-off (0.1 μm 100 kDa 10 kDa polyethersulfone membrane), (ii) the physiochemical characteristics of pomace extracts (particles size distribution, turbidity, etc.) and (iii) the hydrodynamic conditions, namely shear stress. In order to identify the optimal operating conditions for the pilot-scale filtration, the performances of lab-scale filtration were particularly studied in terms of fouling mechanisms (productivity) and phenolic compounds separation (selectivity). (Résumé d'auteur)