Understanding the alkali cold gelation of whey proteins with NaCl and SDS

The alkali cold gelation of whey proteins is studied due to its fascinating rheological gelation profiles, as well as to investigate the existence of an alkali dissolution threshold for protein hydrogels with the protein concentration. Alkali cold gelation is achieved by first producing soluble protein aggregates followed by a sudden increase of the pH. At pH > 11.6 there is a de-gelation step with time following an initial quick gelation step. This dynamic transition involves only the formation of non-covalent interactions between the initial covalently crosslinked aggregates; first they are formed but later on they are destroyed. This mechanistic hypothesis is verified here by adding NaCl and SDS in addition to alkali. A sharp transition of the system modulus can be achieved due non-covalent interactions on soluble disulfide crosslinked aggregates in a narrow protein concentration range.