Adsorption kinetics of some carotenoids at the oil/water interface.
The kinetic analysis of the adsorption of two carotenoids (i.e., ethyl ester of beta-apo-8'-carotenoic acid and beta-carotene, all trans-isomers) from n-hexane solutions at the oil/water interface is presented for several carotenoid concentrations in the oil phase. A new kinetic approach is developed and it addresses the diffusion adsorption associated with a reversible interfacial reaction, which describes the reorientation of surfactant molecules between two conformations. This approach leads to a general analytical expression that contains four physical parameters and describes with high accuracy the experimental dynamic interfacial tensions for the two carotenoids, which independently adsorb from n-hexane phase to the n-hexane/water interface. The calculations give the characteristic times for the carotenoid adsorption at the oil/water interface in terms of diffusion relaxation and kinetic relaxation times. The results explain the long time effects on the adsorption of these carotenoids at the oil/water interface. The data are in substantial agreement with the molecular structure of these carotenoids and with the earlier data recorded for cholesterol adsorption at the n-heptane/water interface. Based on these findings, we propose a molecular mechanism for the interfacial transformation of carotenoid molecules at a hydrophobic/hydrophilic interface.
Joos
Paul
P
Department of Chemistry, University of Antwerp, B-2610 Wilrijk, Belgium.
Tomoaia-Cotisel
Andrada
A
Sellers
Andrew J
AJ
Tomoaia-Cotisel
Maria
M
D000327:Adsorption; D002338:Carotenoids / Q000737:chemistry*; D004058:Diffusion; D007700:Kinetics; D008962:Models, Theoretical; D009821:Oils / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry*; D019207:beta Carotene / Q000737:chemistry
D009821:Oils; D019207:beta Carotene; D014867:Water; D002338:Carotenoids