Effect of pasteurization on the enzymatic cross-linking of milk proteins by microbial transglutaminase in view of milk fat globule membrane isolation

Abstract

This study investigated the prospective effect of pasteurization on the microbial transglutaminase (mTGase) as an enzyme-protein cross linking in view of milk fat globule membrane (MFGM) isolation. Compositional analysis and microstructure properties of MFGM and milk proteins were examined. Pasteurization induced casein cross-linking compared to non-pasteurized sample. MTGase treatment without pretreatment induced the covalent bonds between casein micelles, whether on the surface or between the molecules. Therefore, more casein micelles cross-linked and less micelle liberated into the serum with less aggregation. The cross-linking of whey proteins could be improved by heating as well, which led to an unfolding of the whey proteins, and made them more accessibility for mTGase. The results demonstrated that the pretreatment might improved mTGase-casein cross linking, but in turn affected MFGM obtained proportion adversely. Microstructure properties were investigated for the three layers after ultracentrifugation and showed absorption of non-MFGM proteins onto MFGM surface of all samples. An increase of κ-casein in pasteurized sample was an indicator of a possible κ-casein association with MFGM and/or interaction with whey proteins (β-Lactoglobulin) based upon heating. However, pasteurization might induce more cross-linking of milk proteins, thermal treatment reduced the mTGase ability to show remarkable impact on MFGM and non-MFGM proteins interaction.