Effect of Ozone Treatment on the Structure and Allergenicity of Milk Whey Protein

In this study, we explored the effect of ozone treatment on the structure and allergenicity of milk whey protein. The changes in amino acid composition, sulfhydryl group and disulfide bond contents of whey protein were measured after ozone treatment for 0, 5, 10, 15, 20 and 25 s. Circular dichroism spectroscopy, ultraviolet spectroscopy and fluorescence spectroscopy were applied for analyzing the structural changes. Finally, the ability to bind to specific antibodies in vitro was determined by indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) to evaluate the potential allergenicity. The results showed that ozone treatment reduced the contents of some amino acids in whey protein. It reduced the contents of free sulfhydryl and total sulfhydryl groups from 5.78 to 2.13 µmol/g and from 14.98 to 12.97 µmol/g, respectively, but increased the content of disulfide bonds from 4.60 to 5.42 µmol/g. Spectroscopic analysis showed that the secondary structure of whey protein was changed. At the early stage of ozone treatment, the tertiary structure became loose, but as the treatment time increased, some protein molecules gathered together and the content of disulfide bonds increased, causing the spatial structure of whey protein to return to its original ordered state. The results of ic-LISA showed that the allergenicity of whey protein decreased significantly after ozone treatment. In conclusion, ozone treatment holds great potential in improving the safety of milk-containing foods.