Heat-Induced Gelation of Globular Proteins. 2. Effect of Environmental Factors on Single-Component and Mixed-Protein Gels

Abstract

In the first paper in this series, we investigated heat-induced gelation of single component systems of the globular protein, bovine serum albumin. A series of rheological experiments revealed that we can describe gelation time in terms of two physical parameters, concentration and temperature. In this paper we examine more complex systems, including the effect of pH and ionic strength, on heat-induced gelation of bovine serum albumin (BSA), and another globular protein, β-lactoglobulin (β-Lg). These factors significantly influenced protein gelation, a result which has not been reported in detail before. However, no detailed analysis was possible, because the behavior is very complex. We also consider the extension of both model and experiments to (quasi-) binary mixed systems, viz. the gelation of binary systems chosen from three globular proteins: BSA, β-Lg, and α-lactalbumin (α-La). We have obtained reliable results only for the BSA and β-Lg system because of experimental difficulties. From the data of the BSA/β-Lg system, it was found that gelation behavior changed significantly with the ratio of the two proteins. The change in the gelation time and temperatures was not expressed as a linear equation but required a cross-term. This strongly suggests that current models for the concentration dependence of modulus for mixed biopolymer gels will need to be modified.

The influence of bovine serum albumin on β-lactoglobulin denaturation, aggregation and gelation

“…The interaction between BSA and -lg in heat-induced gels has been studied previously (Tobitani & Ross-Murphy, 1997). It was found that the ratio of the two proteins to each other affected the gelation behaviour with the inclusion of BSA accelerating the formation of the heat-set gels.…”

Molecular mobility and oxygen permeability in amorphous β-lactoglobulin films

“…It was found that the ratio of the two proteins to each other affected the gelation behavior with the inclusion of BSA accelerating the formation of heat-set gels (Tobitani and Ross-Murphy, 1997). Many studies in the past have elucidated this synergy with respect to various other physical parameters but have overlooked the effect of mixing these two differently sized proteins pertaining to the permeability and mobility of the matrix.…”

“…A smaller protein molecule can be easily incorporated into an interfacial film (Suttiprasit, et al, 1992;Hunter et al, 1991). The interaction between BSA and β-Lg in heat-induced gels has been studied previously (Tobitani & Ross-Murphy, 1997). It was found that the ratio of the two proteins to each other affected the gelation behavior, with the inclusion of BSA accelerating the formation of the heat-set gels.…”

Influence of Cosolvent Systems on the Gelation Mechanism of Globular Protein: Thermodynamic, Kinetic, and Structural Aspects of Globular Protein Gelation

“…A series of rheological experiments showed that gelation time can be described in terms of concentration or temperature (Tobitani and Ross-Murphy 1997a) and that the gelation kinetics were fairly accurately portrayed by their model system. In the same paper, they demonstrated that pH and ionic strength had a significant impact on the gelation time of binary mixed systems (BSA, ␤-lactoglobulin, and ␣-lactalbumin) although only reliable results were obtained for the BSA and ␤-Lactoglobulin systems, due to the complexity of the experiments (Tobitani and Ross-Murphy 1997b). It was, however, possible to relate the gelation behavior to the ratio of the 2 proteins present in the binary experimental design .…”