Effect of heat treatment on the detection of intact bovine beta-lactoglobulins by LC mass spectrometry.

Lactoglobulin (LG) is the most abundant protein of the whey fraction of cow's milk, and due to its high nutritional value as well as its technological properties it is widely used as an ingredient in food preparation. As a consequence of heat treatment, milk proteins may undergo structural changes such as protein unfolding and aggregation, in addition to chemical modifications. This, in turn can change the allergenic potential of LG. In this study, the potential of mass spectrometry has been exploited to investigate LG protein modification and stability as a consequence of thermal treatments applied to both standard solutions and milk samples. An investigation into the charge-state distribution in ESI-MS source revealed that, in standard solutions, a higher degree of protonation accompanies increases in the severity of the heat treatment applied. In contrast, the analysis of milk samples revealed a higher stability of the charge-state distribution of LG. However, we observed modification of LG spectra after heating of standard solutions as well as milk samples caused by lactosylation. The degree of LG lactosylation has been investigated in raw milk samples by LC-MS and provides a potential marker to trace heat treatments.