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

Identifier:  imarina:9462794

Handle: https://hdl.handle.net/20.500.11797/imarina9462794

Authors:  Venkatram, R; Castellvi, SD; Rodriguez-Saona, L; Jiménez-Flores, R

Abstract:
The focus of this research was to evaluate changes in the secondary structure of (3-LG induced by supercritical CO2 (ScCO2) treatment of whole milk powder (WMP). Processing conditions of 63 degrees C/200 bar and 75 degrees C/300 bar were chosen for further investigation because they produced the highest reduction in antigenicity, 42.9% +/- 2.83% (+/- SD) at 63 degrees C/200 bar and 54.75% +/- 2.43% at 75 degrees C/300 bar, respectively, via sandwich ELISA. Orbitrap fusion liquid chromatography-MS/MS detected the presence of capric acid under processing conditions of 63 degrees C/200 bar and lactose molecules at 75 degrees C/300 bar, and these post translational modifications were established to be unique to ScCO2 processing. The (3-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 Fourier-transform mid infrared spectroscopy. Results indicated the unfolding of the (3-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 alpha-helices and random coils with a reduction in (3-sheets characteristic to (3-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 (3-LG, indicative of post-translational modifications and were found to be unique to ScCO2 processing.