title: beta-carotene encapsulation in a mannitol matrix as affected by divalent cations and phosphate anion.
abstract: The effects of addition of divalent cations and phosphate buffer on the degree of beta-carotene encapsulation in a mannitol matrix during freeze-drying were analyzed. The degradation rate of encapsulated beta-carotene as a function of % RH and its relationship with the physical state of the matrix during storage at 25 degrees C was also studied. The presence of phosphate salts significantly delayed mannitol crystallization at a highly satisfactory degree during freeze-drying and, consequently, the degree of beta-carotene encapsulation increased. This effect was maintained over quite long time during storage of the freeze-dried samples at 25 degrees C. Unavoidable local variations in water content during 3 years storage caused the decrease of T(g) values and made the crystallization degree to increase. The divalent cations showed a synergistic effect and also modified the kinetics of beta-carotene degradation during storage, increasing its stability. The mechanism of crystallization inhibition likely includes a change in hydrogen bond network or/and change in molecular mobility in the presence of divalent cations and phosphate anions. The degradation rate of beta-carotene in a mannitol/KH(2)PO(4) matrix increased as increasing % RH until a value at which the samples collapsed (75% RH), and then the degradation rate decreased. Collapse phenomena may affect diffusion of oxygen from the surface to the inside of the matrix and increase retention of beta-carotene. Surface color was not an appropriate indicator for beta-carotene degradation, because it was mostly dependent on the optical properties of the matrix, which changed with the degree of matrix hydration and collapse.
authors.affiliation: Departamento de Industrias, Facultad Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Ciudad Universitaria, Buenos Aires, Argentina.
authors.forename: Sonia C
authors.initials: SC
authors.lastname: Sutter
authors.forename: María P
authors.initials: MP
authors.lastname: Buera
authors.forename: Beatriz E
authors.initials: BE
authors.lastname: Elizalde
mesh_terms: D000838:Anions; D002021:Buffers; D002413:Cations, Divalent; D002626:Chemistry, Pharmaceutical; D003116:Color; D003460:Crystallization; D004339:Drug Compounding; D004355:Drug Stability; D004356:Drug Storage; D005079:Excipients / Q000737:chemistry*; D005612:Freeze Drying; D005998:Glycine / Q000737:chemistry; D006813:Humidity; D007700:Kinetics; D008353:Mannitol / Q000737:chemistry*; D008956:Models, Chemical; D010710:Phosphates / Q000737:chemistry*; D017680:Potassium Compounds / Q000737:chemistry*; D013499:Surface Properties; D013678:Technology, Pharmaceutical / Q000379:methods; D014815:Vitamins / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D019207:beta Carotene / Q000737:chemistry*
chemical_list: D000838:Anions; D002021:Buffers; D002413:Cations, Divalent; D005079:Excipients; D010710:Phosphates; D017680:Potassium Compounds; D014815:Vitamins; D019207:beta Carotene; D014867:Water; D008353:Mannitol; C013216:potassium phosphate; D005998:Glycine