Analises reologicas e calorimetricas de sistemas-modelo de proteinas do leite adicionados de carragena e sacarose. / Rheological and Calorimetry Analysis of milk proteins systems-models with carrageenan and sucrose added.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

Interactions among milk proteins-carrageenan-sucrose in aqueous medium were studied in systems at pH 6.7 and submitted to thermal treatment at 70ºC for 30 min. These interactions were studied by evaluation of rheological behavior under oscillatory and steady shear of biopolymers mixture and sucrose during and after gelation. The mechanical properties of gelified products were determined in studies under uniaxial compression at high deformations, allowing a study of the characteristics of rigidity and elasticity of formed gels. The rheological properties were strongly influenced by carrageenan, wich showed interactions with milk proteins and favored the elasticity characteristic of the systems. Whey protein isolate (WPI) favored the formation of a more strength network, while sodium caseinate seemed decrease the rigidity of the gel network, since improved the viscous characteristic of the systems. Sucrose enhanced the interaction between WPI and carrageenan causing the formation of a more elastic network and resistant to the rupture. The interactions among milk proteins-carrageenan-sucrose were evaluated by quantification of state of water in these systems using a differential scanning calorimetry, with determination of free and unfreezable water fractions and the melting temperature onset. The unfreezable water (UFW) and temperature onset were strongly influenced by sucrose, probably by the enhancement of interactions protein-protein and protein-water. The thermal treatment (70ºC for 30 min) supported the interactions between the whey protein with the hydrophilic fractions of casein and their interactions with carrageenan. The interactions between milk proteins after thermal treatment were analysed by polyacrylamide gel electrophoresis related to intermolecular and intramolecular aggregation. This analysis allowed to verify that the protein concentration of the system had an effect on the amount of the free units in solution, making possible the interactions of them with the other systems components, as water and carrageenan.

ASSUNTO(S)

sodium caseinate rheology carrageenan reologia calorimetria caseina calorimetry leite - proteinas sacarose

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