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Reactions between β-Lactoglobulin and Genipin: Kinetics and Characterization of the Products

Qi, Phoebe X., Nuñez, Alberto, Wickham, Edward D.
Journal of agricultural and food chemistry 2012 v.60 no.17 pp. 4327
activation energy, atomic force microscopy, beta-lactoglobulin, crosslinking, desorption, mass spectrometry, pH, polyacrylamide gel electrophoresis, reaction kinetics, temperature
In this paper, we present the first detailed study of the reaction kinetics and the characterization of the products from the endothermic reactions between β-lactoglobulin and genipin. The effects of the concentration, temperature, and pH were investigated. In the temperature range studied, the reaction was approximately a pseudo-first-order with respect to genipin and 0.22-order and −0.24-order with respect to β-lactoglobulin for pH 6.75 and 10.5 with corresponding activation energy (Ea) estimated to be 66.2 +/- 3.8 and 9.40 +/- 0.36 kJ/mol, respectively. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis studies, validated by matrix-assisted laser desorption ionization-time of flight mass spectrometry, showed the presence of oligomeric, i.e., di-, tri-, quadri-, and pentameric, forms of cross-linked β-lactoglobulin by genipin at neutral but not alkaline pH; however, an extensive cross-linked network was not observed, consistent with the atomic force microscopy images. It was demonstrated that the reaction temperature and the concentration of genipin but not that of β-lactoglobulin positively affected the extent of the cross-linking reactions.