Alkali cold gelation of whey proteins. Part I: Sol-gel-sol(-gel) Transitions

Ruben Mercade-Prieto, Sundaram Gunasekaran

Research output: Indexed journal article Articlepeer-review

31 Citations (Scopus)


The cold gelation of preheated whey protein isolate (WPI) solutions at alkaline conditions (pH >10) has been studied to better understand the effect of NaOH in the formation and destruction of whey protein aggregates and gels. Oscillatory rheology has been used to follow the gelation process, resulting in novel and different gelation profiles with the gelation pH. At low alkaline pH, typical sol-gel transitions are observed, as in many other biopolymers. At pH >11.5, the system gels quickly, after ∼300 s, followed by a slow degelation step that transforms the gel to a viscous solution. Finally, there is a second gelation step. This results in a surprising sol- gel-sol-gel transition in time at constant gelation conditions. At very high pH (>12.5), the degelation step is very severe, and the second gelation step is not observed, resulting in a sol-gel-sol transition. The first quick gelation step is related to the quick swelling of the WPI aggregates in alkali, as observed from light scattering, which enables the formation of new noncovalent interactions to form a gel network. These interactions are argued to be destroyed in the subsequent degelation step. Disulfide cross-linking is observed only in the second gelation step, not in the first step.

Original languageEnglish
Pages (from-to)5785-5792
Number of pages8
Issue number10
Publication statusPublished - 19 May 2009
Externally publishedYes


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