Recovery of valuable soluble compounds from washing waters generated during small fatty pelagic surimi processing by membrane processes.

This work focuses on the treatment of washing waters coming from surimi manufacturing using ultrafiltration technology at a laboratory scale. Four membrane materials (poly-ether sulfone, polyacrilonytrile, poly vinylidene fluoride and regenerated cellulose) and 5 Molecular Weight Cut-Off (from 3 to 100 kDa) have been studied at bench laboratory scale using the pilot Rayflow 100, commercialised by Rhodia Orelis. The investigation deals with the ability for membranes to offer a high retention of biochemical compounds (proteins and lipids). Results obtained during adsorption tests showed that the regenerated cellulose material seems to be the most appropriate with regards to pore size reduction due to the protein-adsorption. During the ultrafiltration of the washing water, the regenerated cellulose material leads to the best results, followed by the polyacrylonitrile and poly-vinylidene fluoride materials. Poor results were obtained with polyether sulfone membrane. Compared to the other materials, the regenerated cellulose is the easiest to regenerate, with minimal cleaning water and no chemical treatment necessary. Biochemical characterization of the fractions generated during the ultrafiltration with the polyacrilonytrile, poly vinylidene fluoride and regenerated cellulose membranes showed that all the membranes provided a high recovery rate of the lipids and proteins. The 10 kDa regenerated cellulose membrane had the highest performance and was further evaluated. With such a treatment, the chemical oxygen demand was reduced by 75%. By performing hydrolysis followed by a centrifugation, biochemical composition of the sludge and liquid fraction were modified, producing an insoluble fraction containing fats and few proteins and a soluble fraction containing proteins and few fats. The sludge, initially insoluble, was mainly solubilized during hydrolysis, and lipids and peptides were concentrated by ultrafiltration.