Modifying the microstructure and mechanical properties of whey protein isolate gels using large deformation oscillatory strain
2016 (English)In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 61, 672-677 p.Article in journal (Refereed) Published
The effect of oscillatory shear during heat-induced gelation of whey protein isolate has been investigated. For each gel sample, a single oscillating strain was applied during the gelation process from within the range of 0-1.0. A strain sweep was then used to evaluate the linear viscoelastic region as well as the fracturing properties of each gel. The application of strains lower than ∼0.01 during gelation did not affect the storage modulus while larger strains resulted in lower storage moduli in the linear viscoelastic region. Furthermore, gels produced under small (<0.01) strain amplitudes showed a single fracture point, while gels produced under high (>0.01) amplitude strain were characterised by a two-step fracture pattern. Between the fracture steps, strain hardening behaviour was observed. Confocal laser scanning microscopy was used to identify structural differences between the gels. Greater inhomogeneity was found in gels produced under large amplitude compared to small amplitude strain. It is suggested that localised redistribution of aggregates due to shear during gelation increases the average pore size and possibly creates two distinct types of aggregate structure with differing moduli. The combined effect of heating rate and oscillatory strain was also investigated. We postulate that the mechanism underlying our observations is generic to many gel systems.
Place, publisher, year, edition, pages
2016. Vol. 61, 672-677 p.
Whey protein isolate; Strain-hardening; Gel; Large amplitude oscillatory shear; Microstructure; Heat-set gelation
IdentifiersURN: urn:nbn:se:ri:diva-29207DOI: 10.1016/j.foodhyd.2016.06.017OAI: oai:DiVA.org:ri-29207DiVA: diva2:1086655