Cold‐set whey protein gels induced by calcium or sodium salt addition

Abstract

Cold-set whey protein isolate (WPI) gels formed by sodium or calcium chloride diffusion through dialysis membranes were evaluated by mechanical properties, water-holding capacity and microscopy. The increase of WPI concentration led to a decrease of porosity of the gels and to an increase of hardness, elasticity and water-holding capacity for both systems (CaCl 2 and NaCl). WPI gels formed by calcium chloride addition were harder, more elastic and opaque, but less deformable and with decreased ability to hold water in relation to sodium gels. The non linear part of stress-strain data was evaluated by the Blatz, Sharda, and Tschoegl equation and cold-set gels induced by calcium and sodium chloride addition showed strainweakening and strain-hardening behaviour, respectively. The fractal structure of the gels indicated a weaklink behaviour. For WPI gels results suggest intrafloc links, formed at heating step, which were more rigid than the interfloc links, promoted by salt addition.

Evaluation of Yogurt Microstructure Using Confocal Laser Scanning Microscopy and Image Analysis

“…This also applies to milk gels, where fractal models have been suggested to mathematically model the kinetic behavior of the gel formation (Horne ). Fractal analysis has successfully been used to study the properties of range of different protein gels (Hagiwara and others ; Pugnaloni and others ; Dàvila and others ; Dàvila and Parés ; Kuhn and others ; Torres and others ). Nonetheless, Pugnaloni et al () recognized that although the fractal dimension can be a sensitive descriptor, it is not unique.…”

Structural and functional characterization of solution, gel, and aggregated forms of trypsin in organic solvent-assisted and pH-induced phase changes

“…At high salt concentrations, electrostatic repulsion between protein molecules screened sufficiently so that protein molecules could come closer to form aggregates [18]. Gelation becomes slower as CaCl 2 concentration reached at low CaCl 2 concentrations as in Kuhn's work [11]. Also Kuhn observed aggregates at high CaCl 2 concentrations.…”

“…In a study with whey proteins, it was observed that at low CaCl 2 concentrations (10 mM or lower than 10 mM), gelation was slow and ordered, fine stranded gels were obtained. At high CaCl 2 concentrations (higher than 10 mM), gelation was fast and aggregates were obtained [11]. At high salt concentrations, electrostatic repulsion between protein molecules screened sufficiently so that protein molecules could come closer to form aggregates [18].…”

Cold-set hydrogels made of whey protein nanofibrils with different divalent cations

“…Therefore, cations in addition to cross-linking, particulated the linear WPI fibrils due likely to the flexibility of structures. Similarly, it was reported that soy protein [12] and whey protein [4] cold-set gels prepared with high concentrations of Ca 2+ (>10 mM) had particulate microstructures. The gel made with Zn 2+ had a more compact microstructure than its counterparts made with Ca 2+ or Mn 2+ (Fig.…”

“…CaCl 2 and NaCl are the most common salts for cold gelation of whey proteins [4]. However, monovalent cations are not convenient for fabrication of gels from ␤-lactoglobulin nanofibrils since salt bridges formation (such as fibril − ... + Ca + .…”