Corona is a protein coat that is formed in interaction of microplastics (MP) with proteins. Surrounded by protein corona, MP develop new biological properties like escape from immune system, prolonged persistence in circulation and interference with cellular and molecular processes. It is consisted of two parts, hard corona that is formed after binding of molecules with higher affinity and soft corona, with more loose bound proteins. β-Lactoglobulin (BLG) which constitutes approximately 50% of total whey proteins, despite its high value as a food ingredient, provides significant health risk in patients allergic to bovine milk. The aim was to get a better insight in interactions of BLG as food allergen to selected MPs (polyethylene terephthalate, PET<80um; polypropylene PP 63-180um). Isolated unpasteurised/pasteurised BLG was incubated with MP in vitro, in simulated physiological fluids. Coronas were analysed with reduced SDSPAGE electrophoresis. BLG showed low binding for both MPs. There was some difference in protein content of hard coronas if we compare pasteurized and unpasteurized BLG, for both PP and PET. Percent of bound proteins in hard corona of unpasteurized BLG was about 3% in comparison to 2% in the case of pasteurized BLG. There is a difference in protein profile of hard coronas of both PET and PP incubated with pasteurized BLG compared to hard coronas with unpasteurized BLG. Mass spectrometry analysis of PET hard corona confirmed that bound fragments are BLG C terminal polypeptides. Our results implicate that presence of MPs may influence allergen properties of both pasteurised and unpasteurised BLG.