1. Chymosin-induced hydrolysis of caseins: Influence of degree of phosphorylation of alpha-s1-casein and genetic variants of beta-casein
- Author
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Hein J.F. van Valenberg, Guido Sala, Thom Huppertz, Etske Bijl, Sybren Sikkes, Stijn Jumelet, Kees Olieman, and Toon van Hooijdonk
- Subjects
capillary-zone-electrophoresis ,animal structures ,Proteolysis ,bovine alpha-s1-casein ,Applied Microbiology and Biotechnology ,cheese ,chemistry.chemical_compound ,Hydrolysis ,Capillary electrophoresis ,Casein ,medicine ,protein-composition ,Chymosin ,Food science ,polyproline-ii ,VLAG ,Chromatography ,medicine.diagnostic_test ,individual cows ,secondary structure ,Phosphate ,rennet coagulation properties ,Food Quality and Design ,kappa-casein ,chemistry ,Food Technology ,Phosphorylation ,milk-proteins ,Composition (visual arts) ,Food Science - Abstract
The objective of this study was to investigate the impact of natural variations in αS1-casein and β-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 αS1-casein with eight phosphate groups was hydrolysed compared with αS1-casein with nine phosphate groups in chymosin-induced milk gels. Furthermore, in sodium caseinate solutions, >10% more β-casein A2 was degraded compared with β-casein A1 and B at 50% casein degradation. Proteolysis by chymosin was not impacted by natural variation in the αS1-casein/β-casein ratio. Natural variation in αS1-casein/β-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 αS1-casein or amino acid composition of β-casein caused significant differences in degradation by chymosin, possibly due to changes in physical conformation of caseins.
- Published
- 2014
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