Rheology of Milk Protein Gels and Protein-Stabilized Emulsion Gels Cross-Linked with Transglutaminase

Oscillatory shear measurements have been used to investigate the rheological properties of enzymically cross-linked milk protein gels at neutral pH with and without emulsion droplets. A Ca2+-independent transglutaminase extracted from microorganisms was used as the enzyme source. Storage and loss mo...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 1996-06, Vol.44 (6), p.1371-1377
Main Authors: Dickinson, Eric, Yamamoto, Yukiko
Format: Article
Language:English
Subjects:
Animal, plant, fungal and microbial proteins, edible seaweeds and food yeasts
BETA LACTOGLOBULINA
BETA LACTOGLOBULINE
Biological and medical sciences
CASEINATE
CASEINATOS
COLLOIDE
COLOIDES
DEGRADACION
DEGRADATION
EMULSION
Food industries
Fundamental and applied biological sciences. Psychology
LECITHINE
LECITINAS
PROPIEDADES REOLOGICAS
PROPIEDADES TERMICAS
PROPRIETE RHEOLOGIQUE
PROPRIETE THERMIQUE
PROTEINAS DE LA LECHE
PROTEINE DU LAIT
TRANSFERASAS
TRANSFERASE
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Summary:Oscillatory shear measurements have been used to investigate the rheological properties of enzymically cross-linked milk protein gels at neutral pH with and without emulsion droplets. A Ca2+-independent transglutaminase extracted from microorganisms was used as the enzyme source. Storage and loss moduli are presented for gels formed from enzyme-treated β-lactoglobulin solutions (13 and 14 wt % protein) and β-lactoglobulin-stabilized emulsions (7−9 wt % protein, 32.5 wt % oil). The frequency dependence of the small-deformation elastic moduli of the enzyme-treated gels is weaker than for the equivalent heat-set β-lactoglobulin gels (90 °C for 30 min), and the strain dependence of the elastic moduli of the enzyme-treated gels is of opposite sign to that of the heat-set gels at large deformations. These differences in rheological behavior are consistent with a network consisting of permanent covalent cross-links for the enzyme-induced gels and predominantly physical cross-links for the heat-set gels. Thermal processing after enzyme treatment is very effective in making a strong gel from either a β-lactoglobulin solution or a β-lactoglobulin-stabilized emulsion. Lecithin addition to the β-lactoglobulin-stabilized emulsion gel before enzyme treatment was found to have a weakly positive effect on the gel strength arising from lecithin−protein complexation. When β-lactoglobulin was replaced with sodium caseinate, the rate and extent of enzyme-induced cross-linking was found to increase substantially. Keywords: Emulsion gel; transglutaminase; β-lactoglobulin; sodium caseinate; enzymic cross-linking; thermal denaturation; rheology; lecithin−protein interaction
ISSN:0021-8561
1520-5118
DOI:10.1021/jf950705y