The effect of high pressure microfluidization on the structure and length distribution of whey protein fibrils

The effect of high pressure microfluidization on native β-lactoglobulin (β-lg) or whey protein isolate (WPI), both before and after heat-induced protein fibril formation at pH 2.0, was investigated using atomic force microscopy (AFM), shear birefringence, reversed phase-high pressure liquid chromatography, attenuated total reflectance–Fourier transform infrared spectroscopy and fluorescence spectroscopy. The morphology and length distribution of the fibrils were determined using AFM and flow-induced birefringence, respectively. High pressure (≥50 MPa) microfluidization treatment of β-lg induced ∼30% protein denaturation, accompanied by changes in secondary structure. Fibrils formed from high pressure treated β-lg or WPI were similar in length to fibrils formed from non-pressure treated proteins. High pressure (≥50 MPa) microfluidization of fibrils formed from β-lg or WPI resulted in their breakup into more uniformly sized and much shorter fibrils. Microfluidization pressures of up to 170 MPa resulted in slightly shorter fibrils but did not completely dissociate them.