Liquid side-streams from food industries can be processed and used in food applications and contribute to reduce the environmental footprint of industries. The goal of this study was to evaluate the effectiveness and applicability of protein and phosphorus separation processes, namely microfiltration, ultrafiltration and flocculation, using protein-rich process waters with low (LS) and high (HS) salt content from the processing of salted cod (Gadus morhua). The application of different flocculants (chitosan lactate and Levasil RD442) were evaluated at different concentrations and maturation periods (0, 1 or 3 h). The results showed that different flocculation treatments resulted in different recoveries of the nutrients from LS and HS. Proteins in LS could be most efficiently recovered by using Levasil RD442 0.25% and no maturation period (51.4%), while phosphorus was most efficiently recovered when using Levasil RD442 1.23% and a maturation period of 1 h (34.7%). For HS, most of its protein was recovered using Levasil RD442 1.23% and a maturation period of 1 h (51.8%), while phosphorus was recovered the most using Levasil 1.23% and no maturation period (47.1%). The salt contents allowed interactions through intermolecular forces with Levasil RD442. The ultrafiltration method was effective on HS since it recovered higher percentages of nutrients in the retentate phase (57% of the protein and 46% of the phosphorus) compared to LS.
Keywords: flocculants; flocculation; microfiltration; phosphorus; protein; ultrafiltration.