Heat-Induced Gelation of Globular Proteins:  4. Gelation Kinetics of Low pH β-Lactoglobulin Gels

Abstract

Particulate gels, especially those formed from heating protein solutions, have been extensively investigated over the years. One focus of this work has been, for commercial reasons, on rather crude mixtures of the main milk protein components (whey isolates), -lactoglobulin and R-lactalbumin. Moreover, most previous work has concentrated on examining structural and rheological properties of fully cured gels. In the present paper, a less pragmatic approach is adopted, and the gelation behavior of solutions of relatively pure -Lg (under isothermal heating at 80°C) are investigated over a range of concentrations and pH values (7, 3, 2.5, and 2). Both gel time and limiting (extrapolated) long-time modulus data were measured and were considered in light of currently available models for the gelation process. Whereas the gel time data was described best by a semiempirical model introduced by one of the authors, the modulus data could be quite adequately understood in terms of branching theory (cascade theory description) results, corresponding well with conclusions from structural studies of the gels using negative-staining electron microscopy. A fractal model was much less successful in this respect. Gel time data, it seems, reflect much more sensitively the details of network assembly in a particular case. Modulus-concentration data, on the other hand, are less determined by gel type and more universal.

Mechanical characterization of network formation during heat-induced gelation of whey protein dispersions

“…The drawback of this kind of analysis is that obtained self-similarity is guaranteed only within the examined range and the relevance with the gelation kinetics is scarce. 55 It is, in fact, expected that the value of the fractal dimension itself changes with concentration, observation length scale, and aging (postgelation reactions). 56,57 There is no doubt that fractal dimension is not a magic number but solely one of the parameters required to characterize gel network structures (e.g., lower and upper limits of self-similarity, strand thickness, pore size distribution, etc.…”

Tuning the properties of β-lactoglobulin nanofibrils with pH, NaCl and CaCl2

“…Ionic strength and pH affect both the kinetics of fibril formation (Arnaudov & De Vries, 2007;Aymard et al, 1999) and the morphology of fibrils (Arnaudov & de Vries, 2006;Aymard et al, 1999;Durand, Gimel, & Nicolai, 2002;Kavanagh et al, 2000b, Mudgal, Daubert, & Foegeding, 2009. Macroscopic properties of b-lactoglobulin fibril dispersions/gels such as turbidity (Sagis et al, 2002), gel strength (Kavanagh, Clark, & Ross-Murphy, 2000a) and critical percolation concentration (Sagis, Veerman, & van der Linden, 2004) are also affected by ionic strength and pH.…”

Espalhamento e secagem de filme de amido-glicerol-fibra preparado por "tape-casting"

“…Para suspensões com temperaturas de até 50ºC, observou-se que o módulo de elasticidade (G') foi superior ao módulo viscoso G", em todo o espectro de frequências de oscilação avaliado, o que, de acordo com Kavanagh et al (2000), mostra a importância da componente elástica da suspensão. Nas temperaturas acima de 50ºC, ocorreu um cruzamento das curvas, em uma estreita faixa de frequências (0,01, 0,02 e 0,03 rad s -1 , para 50, 60 e 70ºC (Figura 2 B).…”