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

• Published in: Journal of agricultural and food chemistry 2012-05, Vol.60 (17), p.4327-4335
• Main Authors: Qi, Phoebe X, Nuñez, Alberto, Wickham, Edward D
• Format: Article
• Language: English
• Subjects: activation energy; atomic force microscopy; beta-lactoglobulin; Biological and medical sciences; Calorimetry, Differential Scanning; Cross-Linking Reagents; crosslinking; desorption; Food industries; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Iridoids - chemistry; Kinetics; Lactoglobulins - chemistry; mass spectrometry; Microscopy, Atomic Force; Milk and cheese industries. Ice creams; polyacrylamide gel electrophoresis; reaction kinetics; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Temperature; Thermodynamics
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf300311k

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 (E a) 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.