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Research article - Peer-reviewed, 2020

Effects of milk proteins and posttranslational modifications on noncoagulating milk from Swedish Red dairy cattle

Nilsson, K.; Johansen, L. Buhelt; de Koning, D. J.; Duchemin, S. I.; Hansen, M. Stenholdt; Stalhammar, H.; Lindmark-Mansson, H.; Paulsson, M.; Fikse, W. F.; Glantz, M.

Abstract

Milk that does not coagulate after rennet addition, also called noncoagulating (NC) milk, is unwanted in cheese production due to prolonged processing time. Amounts of whey and casein proteins, genetic variants, as well as posttranslational modifications (PTM) of proteins are all contributing factors in rennet -induced coagulation of milk. In this study, we conducted a wide- ranging investigation of milk proteins in milk samples from 616 Swedish Red dairy cattle using liquid chroma- tography-high resolution mass spectrometry. Relative concentration of proteins, genetic variants, and PTM were compared between NC milk and coagulating milk. The PTM investigated were phosphorylation of caseins and glycosylation of kappa-casein. Several genetic variants and PTM were found, including rare phosphorylation variants of the alpha(S)-caseins. Genetic variants were found to effect the expressed amount of different proteins. Further, the effect of protein amounts and PTM on a binary NC milk trait was modeled using a generalized linear model. The model showed that NC milk significantly correlated with higher relative concentrations of alpha-lactalbumin and beta-casein and lower relative concentrations of beta-lactoglobulin and kappa-casein. Regarding PTM of caseins, an effect on NC milk from a lower relative concentration of alpha(S1)-casein with 8 phosphate groups were found, even though an effect from total relative concentration of alpha(S1)-casein was not found. This study has provided insights into protein variants and PTM important for NC milk to improve this undesirable property.

Keywords

milk coagulation; protein profile; genetic variants; posttranslational modifications

Published in

Journal of Dairy Science
2020, Volume: 103, number: 8, pages: 6858-6868
Publisher: ELSEVIER SCIENCE INC