The physical behaviour of food protein’s supramolecular structures during freezedrying
2011
Passot, Stéphanie | Fonseca, Fernanda | Brothier, Fabien
Many proteins are able to self-assembly into well-defined supramolecular structures. We have previouslyshown that two food globular proteins with highly homologous tertiary structures and opposite electriccharges, i.e. lysozyme and a-lactalbumin, interact under specific conditions of temperature and pH andgenerate spherical microparticles. The objective of this study was to investigate the stability of the lysozyme- a-lactalbumin microparticles during lyophilisation, one example of food processes. Solutions of proteinmicroparticles without and with addition of protective molecules such as sucrose or matlodextrin werefreeze-dried under conservative conditions in a pilot plant and samples were removed at each step of theprocess: after freezing, sublimation and desorption. The morphology and the particle size distribution of theprotein microparticles were investigated by direct optical observation under a microscope and by using aCoulter counter. The freezing (and thawing) appeared to be the most damaging steps with the formation ofclusters or agglomerates of microparticles. Addition of sucrose or maltodextrin sharply reduced the formationof particles agglomerates after freezing by limiting the cryoconcentration of the particles and trapping themin an amorphous matrix. Maltodextrin seemed to be a more efficient protective molecule than sucrose forpreserving the stability of the protein microparticles during the freeze-drying process.
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