Résumé :
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Gel formation and the melting of kappa-carrageenan in the presence of beta-lactoglobulin were investigated using dynamic theological techniques as well as a sequence of experimental sweeps of time-temperature, frequency, and strain. The blends, initially prepared at 45 °C, show homogeneous mixtures, which then lead to the formation of a gelled kappa-carrageenan network containing inclusions of native beta-lactoglobulin during the controlled cooling phase from 45 to 20 °C. In its native state, the protein seems to weaken the polysaccharide network, particularly when present in high concentration. Upon subsequent heating to 90 °C, mixed gels presented a biphasic profile: the first phase, characterized by a decrease in the storage modulus, involves a heat-induced meltdown of the kappa-carrageenan network, whereas the second phase, exhibiting an increase in the storage modulus, corresponds to the build up of a protein network. The DSC analysis showed that each biopolymer undergoes specific conformational changes. These results are highly indicative of the lack of association between the biopolymers and suggest a phase separation and gelation in beta-lactoglobulin and kappa-carrageenan mixtures.
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