Evaluating secondary structure changes in beta-lactoglobulin induced by supercritical CO2 treatment

This is the authors' abstract. We don't add key points for this paper.

The focus of this research was to evaluate changes in the secondary structure of β-LG induced by supercritical CO2 (ScCO2) treatment of whole milk powder (WMP). Processing conditions of 63°C/200 bar and 75°C/300 bar were chosen for further investigation because they produced the highest reduction in antigenicity, 42.9% ± 2.83% at 63°C/200 bar and 54.75% ± 2.43% at 75°C/300 bar, respectively, via sandwich ELISA. Orbitrap fusion liquid chromatography-MS/MS detected the presence of capric acid under processing conditions of 63°C/200 bar and lactose molecules at 75°C/300 bar, and these post translational modifications were established to be unique to ScCO2 processing. The β-LG was isolated from reconstituted WMP via isoelectric precipitation and membrane filtration, and secondary structure analysis was conducted via UV-absorption, intrinsic and extrinsic, circular dichroism, and FT-MIR spectroscopy. Results indicated the unfolding of the β-LG molecule, with exposure of Trp residuals to the exterior and an increase in surface hydrophobicity of the protein molecule. Circular dichroism spectroscopy results highlighted an increase in α-helices and random coils with a reduction in β-sheets characteristic to β-LG and thus highlighting significant changes in the secondary structure of the protein. Glycoprotein formation and caprylation had the most significant effects on the amide I and II regions of β-LG, indicative of posttranslational modifications and were found to be unique to ScCO2 processing.