Effect of high-intensity pulse electric fields on denaturation of bovine whey proteins

The effect of pulsed electric field (PEF) processing on denaturation of bovine whey proteins has been studied. Protein concentration was determined by radial immunodiffusion and lactoperoxidase activity by a spectrophotometric technique. For the five proteins studied (beta-lactoglobulin, alpha-lactalbumin, lactoperoxidase, IgG and lactoferrin), no significant differences were found in the concentration of immunoreactive proteins between untreated milk or whey samples and those subjected to a treatment of 50, 100 and 200 pulses at 37.6 kV/cm. Likewise, lactoperoxidase activity did not change under PEF conditions tested. The effect of pasteurization treatments on whey proteins was also determined for comparison with PEF treatments. Treatment at 65 degrees C for 30 min and at 75 degrees C for 15 s markedly decreased concentration of lactoferrin to 53% and 58% of the initial value when heated in whey. Besides, both treatments caused a considerable decrease of concentration and enzymatic activity of lactoperoxidase treated in milk or whey. Heat treatments at 80 and 90 degrees C for 15 s produced a severe loss of immunoreactivity of IgG, lactoferrin and lactoperoxidase. The application of PEF treatments for milk preservation could prevent changes in structure and functionality of whey proteins with biological activity that are heat-sensitive.