The spread and adsorbed layers of β-lactoglobulin (BLG) microgel were investigated by the dilational surface rheology, atomic force microscopy and optical microscopy. It is shown that only careful purification of the BLG microgel dispersion gives a possibility to observe distinctions between the properties of spread layers of BLG nano- and micro particles on the one hand, and the properties the layers of BLG molecules on the other hand. The BLG particles do not have a thick and soft corona like poly(N-isopropylacryl) microgel. The fluctuations of the surface pressure of the BLG microgel layers at high surface compressions are a consequence of a special collapse mechanism, which has not observed earlier for the layers of both soft and rigid nano- and microparticles.