Study of the shear and extensional rheology of casein, waxy maize starch and their mixtures

• Published in: Food hydrocolloids Vol. 21; no. 5; pp. 716 - 725
• Main Authors: Chan, Philip Shiu-Kin, Chen, Jianshe, Ettelaie, Rammile, Law, Zerah, Alevisopoulos, Stefan, Day, Eddy, Smith, Sam
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 2007; Elsevier
• Subjects: Biological and medical sciences; biopolymers; Casein; chemical concentration; corn starch; Extensional rheology; Food additives; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; mixtures; Phase separation; rheological properties; Shear rheology; shear stress; Starch and starchy product industries; surface tension; temperature; thermodynamics; Trouton ratio; viscosity; waxy corn; Waxy maize starch; Casein; Extensional rheology; Waxy maize starch; Shear rheology; Phase separation; Trouton ratio; Shear; Starch; Corn; Mixture; Milk protein; Cereal; Carbohydrate; Polysaccharide; Rheological properties
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2007.02.001

This work investigated the shear and uniaxial extensional flow behaviour of aqueous casein and phosphated waxy maize starch systems as a function of the deformation rate, biopolymer concentration and the temperature. Trouton ratios were calculated to compare different responses of biopolymers to the shear and extensional deformation. It was found that the casein system (20% w/w) had a much higher and linearly increasing Trouton ratio against the log increase of strain rate. The starch system (35% w/w) had a Trouton ratio close to 3 at low strain rates, but increasing linearly once the strain rate exceeded 2 s −1. The apparent shear and extensional viscosity showed an exponential increase with the concentration for both biopolymers, with casein being more concentration dependent. Their Trouton ratios were also very much concentration dependent: remained close to 3 at low biopolymer levels, but increased significantly at higher concentrations. Temperature variation experiments demonstrated that the flow properties of casein and waxy maize starch follow an Arrhenius relationship, with casein showing stronger temperature dependence than starch. While casein systems displayed a decrease in Trouton ratio with temperature increase, waxy maize starch had the opposite behaviour. The mixing of casein–waxy maize starch resulted in higher apparent extensional viscosities and higher Trouton ratios than single biopolymer systems.