Impact of thermal processing on stability of milk glycoproteins

摘要

Bovine glycosylated caseinomacropeptide (gCMP) as well as glycoproteins from the milk fat globule membrane (MFGM) received a lot of interest due to their nutritional and technological properties as well as their potential as ingredient for food applications [1-3]. Bioactive properties of milk glycoproteins like antibacterial effects are reported to be closely associated with their structure in terms of the attached glycans. Furthermore, technological properties are influenced by the carbohydrate side chains [2, 4]. However, during product manufacturing milk glycoproteins can be modified. Therefore, processing that influences the degree of glycosylation leads to alterations of bioactivity and techno-functional properties of gCMP and MFGMglycoproteins (MFGM-GP) and accordingly to glycoprotein-containing products. Hence, gCMP and MFGMGP were studied for their glycan stability during heat treatment and in dependence of pH. Process stability was analyzed by quantifying the liberation of the terminal carbohydrate, N-acetylneuraminic acid (Neu5Ac), from gCMP and MFGM-GP. The results clearly show that thermal stability of the glycoproteins was strongly influenced by pH. Optimal heating conditions were reached at neutral pH. At acidic pH conditions hydrolysis of glycans from the protein backbone took place during thermal treatment. Hence, structural changes of gCMP and MFGM-GP occur and with it the alterations of functional and technological properties.