Rheology of ι-carrageenan gels containing caseins
1996; Elsevier BV; Volume: 10; Issue: 2 Linguagem: Inglês
10.1016/s0268-005x(96)80029-4
ISSN1873-7137
AutoresM.G. Lynch, Daniel M. Mulvihill,
Tópico(s)Polysaccharides Composition and Applications
ResumoSmall strain oscillatory techniques were used to study the effects of added sodium caseinate or casein fractions on the rheology of 1% ι-carrageenan gels containing 0.01 moll dm3 CaCl2 or 0.02 moll dm3 KCl at 5°C. The mechanical spectra (frequency dependence of G′ (storage modulus), G″ (loss modulus) and tan δ (G″/G′)) of all mixed casein/ι-carrageenan systems differed from those of corresponding ι-carrageenan gels. Added κ-casein transformed a relatively weak Ca2+-free ι-carrageenan gel to a strong, elastic gel, indicating increased crosslinking which is attributed to electrostatic interactions between κ-casein and ι-carrageenan. Changes to the rheology of Ca2+-free ι-carrageenan gels on addition of αs- or β-casein are attributed to excluded volume effects, with monomeric β-casein exerting a greater excluded volume effect than aggregated αs-casein. Added αs-or β-casein also altered the rheology of Ca2+-containing ι-carrageenan gels, attributable to Ca2+-mediated interactions of αs- and β-caseins with ι-carrageenan. The effects of these caseins were reduced on dephosphorylation of the caseins indicating the importance of phosphate groups for the interaction of these caseins with ι-carrageenan in systems containing Ca2+. Low levels of sodium caseinate increased both the rigidity and elasticity of Ca2+-free ι-carrageenan gels and Ca2+-containing ι-carrageenan gels. However, higher levels of sodium caseinate reduced elasticity in both cases. Sodium caseinate had a greater effect on the rheology of ι-carrageenan gels in the presence of Ca2+, presumably due to Ca2+-mediated interactions of αs- and β-caseins with ι-carrageenan.
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