Influence of pH and operation variables on biogenic amines nanofiltration

This work analyzes the ability of nanofiltration membranes to separate biogenic amines. Biogenic amines evolve in fermented foods and beverages and may have toxic effects. Model solutions of putrescine, histamine and tyramine in a wide range of pH were tested using an organic membrane with a molecular weight cut-off (MWCO) of 1000 Da and an isoelectric point (IEP) of about 7. Feed pH strongly influenced solute rejection. In acidic conditions up to pH 4, rejections of around 98, 96 and 90% were attained for histamine, putrescine and tyramine, respectively. Very low rejections of 5–10% were found at neutral pH and only moderate 20–40% rejections were generally observed in the alkaline zone. Furthermore, proton rejection was negative up to pH 6 and positive above this pH, regardless of the amine tested. The results were discussed in terms of the changes that pH produces on the electrical charge of both membrane and amines, and consequently on the membrane–solute interactions. Electrostatic repulsion was shown to be the dominant mechanism governing the separation process. In contrast, sieving exclusion did not seem to play a significant role.