Antigenicity and functional properties of β-lactoglobulin conjugated with fructo-oligosaccharides in relation to conformational changes

Bovine β-lactoglobulin (β-LG) was conjugated with fructo-oligosaccharides (FOS) by Maillard reaction to investigate the relationship among antigenicity, functional properties, and conformational changes of β-LG. When comparing the antigenicity of β-LG conjugated with FOS at different ratios, the lowest antigenicity of β-LG was observed at a ratio of 1:4, which was about 7 times lower than that of the control β-LG. Thus, the ratio of 1:4 was chosen to conjugate β-LG with FOS, and the functional properties and conformational changes of β-LG-FOS conjugates were investigated. The functional properties (solubility, emulsifying ability, and emulsion stability) of β-LG were enhanced after conjugation with FOS. Furthermore, the molecular weight of β-LG increased from 18.4 to 19.9 kDa after conjugation with FOS, as evaluated by sodium dodecyl sulfate-PAGE and mass spectrometry. Partial unfolding of β-LG occurred after conjugation with FOS, as reflected by the quenching of fluorescence, the red-shift of fluorescence spectra, and the increase of β-strands, which may contribute to the decrease in antigenicity and the improvement of functional properties.