Power Law Behavior of Structural Properties of Protein Gels

Abstract

Whey proteins are globular, heat-sensitive proteins. The gel structure, the formation of this structure, and the rheological properties of particulate whey protein isolate (WPI) gels have been investigated. On increasing the NaCl concentration, the permeability of the WPI gels increased, indicating a coarsening of the gel structure, confirmed by confocal scanning laser microscopy pictures. Only a part of the total amount of protein present contributed to the gel network at the gel point (the primary spatial structure). Large variations were observed in the amount of aggregated material at the gel point (and thus the primary spatial structure) as a function of NaCl concentration, due to differences in the kinetics of the denaturation/aggregation process. After the gel point more protein is incorporated in the gel network by "thickening" the strands in the gel and "decorating" the pores in the gel, apparently without changing the gross spatial structure. Power law behavior was found for the permeability dependence of aged gels on the amount of aggregated material at the gel point. For various salt concentrations the curves coincided to one master curve. This power law behavior is consistent with a primary spatial structure of fractal flocs with a fractal dimensionality of 2.4. The elastic modulus is remarkably related (via a power law) with the total amount of protein contributing to the gel network, in contrast to permeability.

Properties of Hydrogels Derived from Cationic Analogues of Bile Acid: Remarkably Distinct Flowing Characteristics

“…The combination of the observation of an exponent different from 2 of the G′ vs C scaling law and that of fibers by SEM (accounting for the description of the linear backbones of the flocs) is a good argument to consider the colloidal gel model involving fractal flocs as a possible theoretical context. It appears that n ∼ 5 is similar to the exponent observed for whey protein in salted gels (n ∼ 5) 40 and comparable to that obtained for boehmite alumina gels (n ∼ 4.2). 38 The trend of a decreasing limit of linearity with increasing concentration indicated that the latter alumina gel system was in the strong-link regime.…”

Properties of Hydrogels Derived from Cationic Analogues of Bile Acid: Remarkably Distinct Flowing Characteristics

“…The combination of the observation of an exponent different from 2 of the G′ vs C scaling law and that of fibers by SEM (accounting for the description of the linear backbones of the flocs) is a good argument to consider the colloidal gel model involving fractal flocs as a possible theoretical context. It appears that n ∼ 5 is similar to the exponent observed for whey protein in salted gels (n ∼ 5) 40 and comparable to that obtained for boehmite alumina gels (n ∼ 4.2). 38 The trend of a decreasing limit of linearity with increasing concentration indicated that the latter alumina gel system was in the strong-link regime.…”

Kinetics of Aggregation and Gelation of Globular Proteins after Heat-Induced Denaturation

“…The experimental results are well described by the calculated values; see the solid line in Figure 13. For comparison, we also show the results obtained by Verheul et al 43 on a whey isolate which shows the same qualitative behavior.…”

“…The experimental results are well described by the calculated values; see the solid line in Figure . For comparison, we also show the results obtained by Verheul et al on a whey isolate which shows the same qualitative behavior.

13 Aggregate concentration at the gel point as a function of the total β-lg concentration for various temperatures indicated in the text (pH 7, 0.1 M CH 3 COONH 4 ).

…”

Gelation of Edible Blue-Green Algae Protein Isolate ( Spirulina platensis Strain Pacifica): Thermal Transitions, Rheological Properties, and Molecular Forces Involved

“…We will return to this point below. It is notable that the above scaling exponents of elastic moduli versus protein concentration are within the range of exponents observed for various protein gels, between 2 and 7 depending on experimental conditions (43,44).…”

Properties of Hydrogels Derived from Cationic Analogues of Bile Acid: Remarkably Distinct Flowing Characteristics

“…The combination of the observation of an exponent different from 2 of the G′ vs C scaling law and that of fibers by SEM (accounting for the description of the linear backbones of the flocs) is a good argument to consider the colloidal gel model involving fractal flocs as a possible theoretical context. It appears that n ∼ 5 is similar to the exponent observed for whey protein in salted gels (n ∼ 5) 40 and comparable to that obtained for boehmite alumina gels (n ∼ 4.2). 38 The trend of a decreasing limit of linearity with increasing concentration indicated that the latter alumina gel system was in the strong-link regime.…”

Kinetics of Aggregation and Gelation of Globular Proteins after Heat-Induced Denaturation

“…The experimental results are well described by the calculated values; see the solid line in Figure 13. For comparison, we also show the results obtained by Verheul et al 43 on a whey isolate which shows the same qualitative behavior.…”

“…The experimental results are well described by the calculated values; see the solid line in Figure . For comparison, we also show the results obtained by Verheul et al on a whey isolate which shows the same qualitative behavior.

13 Aggregate concentration at the gel point as a function of the total β-lg concentration for various temperatures indicated in the text (pH 7, 0.1 M CH 3 COONH 4 ).

…”

Gelation of Edible Blue-Green Algae Protein Isolate ( Spirulina platensis Strain Pacifica): Thermal Transitions, Rheological Properties, and Molecular Forces Involved

“…We will return to this point below. It is notable that the above scaling exponents of elastic moduli versus protein concentration are within the range of exponents observed for various protein gels, between 2 and 7 depending on experimental conditions (43,44).…”

Properties of Hydrogels Derived from Cationic Analogues of Bile Acid: Remarkably Distinct Flowing Characteristics

“…The combination of the observation of an exponent different from 2 of the G′ vs C scaling law and that of fibers by SEM (accounting for the description of the linear backbones of the flocs) is a good argument to consider the colloidal gel model involving fractal flocs as a possible theoretical context. It appears that n ∼ 5 is similar to the exponent observed for whey protein in salted gels (n ∼ 5) 40 and comparable to that obtained for boehmite alumina gels (n ∼ 4.2). 38 The trend of a decreasing limit of linearity with increasing concentration indicated that the latter alumina gel system was in the strong-link regime.…”

Kinetics of Aggregation and Gelation of Globular Proteins after Heat-Induced Denaturation

“…The experimental results are well described by the calculated values; see the solid line in Figure 13. For comparison, we also show the results obtained by Verheul et al 43 on a whey isolate which shows the same qualitative behavior.…”

“…The experimental results are well described by the calculated values; see the solid line in Figure . For comparison, we also show the results obtained by Verheul et al on a whey isolate which shows the same qualitative behavior.

13 Aggregate concentration at the gel point as a function of the total β-lg concentration for various temperatures indicated in the text (pH 7, 0.1 M CH 3 COONH 4 ).

…”

Gelation of Edible Blue-Green Algae Protein Isolate ( Spirulina platensis Strain Pacifica): Thermal Transitions, Rheological Properties, and Molecular Forces Involved

“…We will return to this point below. It is notable that the above scaling exponents of elastic moduli versus protein concentration are within the range of exponents observed for various protein gels, between 2 and 7 depending on experimental conditions (43,44).…”