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| - Structural Collapse Prevents β-Carotene Loss in a SupercooledPolymeric Matrix
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| - The kinetics of degradation and surface color changes of β-carotene encapsulated in a polymericmatrix (PVP-40) and its relationship with physical changes (manifested as structural collapse) of thematrix were studied during storage of samples at several water activities at constant temperature.The degradation rate constants obtained decreased with an increase in the relative humidity (RH) ofthe storage atmosphere. β-Carotene losses were observed mainly at RHs below the glass transitiontemperature (Tg) of the corresponding systems, and the lower degradation constant rates wereobserved under conditions where the matrices were fully plasticized (i.e., rubbery) and collapsed(RH, 64 and 75%). An inverse correlation was observed between collapse and degradation rateconstants. The results presented here indicated that the molecular mobility of the matrix is not ratelimiting for the degradation of β-carotene. Factors such as microstructure and porosity of the polymericmatrix may be more important as modifiers of kinetic reactions. Surface color was not a sensitiveindicator of β-carotene retention, because it was mostly affected by the degree of matrix hydrationand collapse phenomena. Keywords: Encapsulation; β-carotene; collapse; molecular mobility; glass transition
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