CONICET | Buscador de Institutos y Recursos Humanos

The objective of this work was to study the effect of typeof acid (hydrochloric, lactic, citric and acetic) on theformation of soluble complexes of thermally denatured -lactoglobulin (-lg) and carboxymethylcellulose (CMC). βlg was prepared at different concentrations (0.125, 0.250and 0.500% w/w) at pH 7.0 and heated at 80 ° C for 15minutes. The complexes were formed with 0.3% (w/w) ofCMC and two percentages of protein (0.125 and 0.250)at pH 4. They were characterized by UV-visible(absorbance at 600 nm), fluorescence, dynamic lightscattering (DLS), flow rheology and FTIR. The complexesshowed greater coefficient of consistency, K, and lowerpseuplastic index (n) than CMC pure. The 0.125 -lg/0.3CMC complexes formed with acetic or lactic acids hadthe highest K and the lowest n. The 0.250 -lg/0.3 CMCcomplexes formed with acetic acid had the highest K andthe lowest n. Interestingly, K decreased with the proteinratio increase for the -lg/CMC complexes formed withHCl. The NaCl addition at 100 mM or more decreased theturbidity of all soluble complexes. However, thecomplexes 0.125 -lg/0.3 CMC formed with acetic acidand the complexes 0.250 -lg/0.3 CMC formed withacetic, lactic and citric acid showed stable curves in thefluorescence tests. The FTIR spectra of the complexesshowed electrostatic interactions between themacromolecules. It is concluded that the complexesformed with acetic acid have high electrostatic interaction,even in presence of salt, for both concentrations ofproteins studied. On the other hand, the complexes 0.250B-lg/0.3CMC formed with HCl revealed an excess ofprotein that lowered the viscosity of the systems. Thisstudy shows that the type of acid used in the formation of asoluble complex is as essential as the proteinpolysaccharide ratio, the pH or the nature of the polymers.This knowledge will be used in the future for thereplacement of fat in food systems like yogurt.