Chymosin-induced hydrolysis of caseins: Influence of degree of phosphorylation of alpha-s1-casein and genetic variants of beta-casein

E. Bijl, H.J.F. van Valenberg, S. Sikkes, S. Jumelet, G. Sala, K. Olieman, A.C.M. van Hooijdonk, T. Huppertz

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The objective of this study was to investigate the impact of natural variations in aS1-casein and b-casein composition of milk on chymosin-induced hydrolysis of these caseins in milk gels and in sodium caseinate solutions. At 50% casein degradation, 15% more of aS1-casein with eight phosphate groups was hydrolysed compared with aS1-casein with nine phosphate groups in chymosin-induced milk gels. Furthermore, in sodium caseinate solutions, >10% more b-casein A2 was degraded compared with bcasein A1 and B at 50% casein degradation. Proteolysis by chymosin was not impacted by natural variation in the aS1-casein/b-casein ratio. Natural variation in aS1-casein/b-casein ratio did not impact upon firmness and gel strength in milk gels. Overall, comparison of sodium caseinate solutions to milk gels showed that differences in either phosphorylation of aS1-casein or amino acid composition of b-casein caused significant differences in degradation by chymosin, possibly due to changes in physical conformation of caseins.
Original languageEnglish
Pages (from-to)215-221
JournalInternational Dairy Journal
Issue number2
Publication statusPublished - 2014



  • capillary-zone-electrophoresis
  • rennet coagulation properties
  • bovine alpha-s1-casein
  • protein-composition
  • milk-proteins
  • kappa-casein
  • secondary structure
  • individual cows
  • polyproline-ii
  • cheese

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