European Biophysics Journal

, Volume 35, Issue 6, pp 503–509 | Cite as

Size distribution of pressure-decomposed casein micelles studied by dynamic light scattering and AFM

  • Ronald Gebhardt
  • Wolfgang Doster
  • Josef Friedrich
  • Ulrich Kulozik
Article
First Online:
Received:
Revised:
Accepted:

Abstract

Reversible and irreversible states of pressure-dissociated casein micelles were studied by in situ light scattering techniques and ex situ atomic force microscopy. AFM experiments performed at ambient pressure reveal heterogeneities across the micelle, suggesting a sub-structure on a 20 nm scale. At pressures between 50 and 250 MPa, the native micelles disintegrate into small fragments on the scale of the observed sub-structure. At pressures above 300 MPa the micelles fully decompose into their monomeric constituents. After pressure release two discrete populations of casein aggregates are observed, depending on the applied initial pressure: Between 160 and 240 MPa stable micelles with diameters near 100 nm without detectable sub-structures are formed. Casein micelles exposed to pressures above 280 MPa re-associate at ambient pressure yielding mini-micelles with diameters near 25 nm. The implications concerning structural models are discussed.

Keywords

Casein micelles High pressure Dynamic light scattering Atomic force microscopy 
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Notes

Acknowledgements

This work was supported by the Deutsche Forschungsgemeinschaft: Forschergruppe FR 456/25–4, project A1 and SFB 533, project B11.

References

  1. Anema SG, Lee SK, Schrader K, Buchheim W (1997) Effect of pH on the turbidity of pressure-treated calcium caseinate suspensions and skim milk. Milchwissenschaft 52:141–146Google Scholar
  2. Anema SG, Lowe EK, Stockmann R (2005) Particle size changes and casein solubilisation in high-pressure-treated skim milk. Food Hydrocolloids 19:257–267CrossRefGoogle Scholar
  3. Cheftel JC, Tiehbaud M, Dumay E (2002) High pressure-low temperature processing of foods: a review, p. 327 – 340 In: Winter R (ed) Advances in high pressure bioscience and biotechnology II, Springer Verlag and other articles in this volumeGoogle Scholar
  4. Dalgleish DG, Spagnuolo PA, Douglas Goff H (2004) A possible structure of the casein micelle based on high-resolution field-emission scanning electron microscopy. Int Dairy J 14:1025–1031CrossRefGoogle Scholar
  5. Desobry-Banon S, Richard F, Hardy J (1994) Study of acid and rennet coagulation of high pressurized milk. J Dairy Sci 77:3267–3274Google Scholar
  6. Doster W, Friedrich J (2005) Pressure-temperature phase diagrams of proteins. In: Buchner J, Kiefhaber Th (eds) Protein folding handbook, Wiley-VCH, Berlin pp 99–126Google Scholar
  7. Gaucheron F, Famelart MH, Mariette F, Raulot K, Michel F, Le Graet Y (1997) Combined effects of temperature and high pressure treatments on physicochemical characteristics of skim milk. Food Chem 59:439–447CrossRefGoogle Scholar
  8. Gebhardt R, Doster W, Kulozik U (2005) Pressure-induced dissociation of casein micelles: size distribution and effect of temperature. Braz J Med Biol Res 38:1209–1214CrossRefGoogle Scholar
  9. Holt C, de Kruif CG, Tuinier R, Timmins PA (2003) Substructure of bovine casein micelles by small-angle X-ray and neutron scattering. Colloids Surf A 213:275–284CrossRefGoogle Scholar
  10. Horne DS (1998) Casein Interactions: casting light on the black boxes, the structure in dairy products. Int Dairy J 8:171–177CrossRefGoogle Scholar
  11. Horne DS (2003) Casein micelles as hard sheres: limitations of the model in acidified gel formation. Colloids Surf A: Physicochem Eng Aspects 213:255–263CrossRefGoogle Scholar
  12. Huppertz T, Kelly AL, Fox PF (2002) Effects of high pressure on constituents and properties of milk. Int Dairy J 12:561–572CrossRefGoogle Scholar
  13. Huppertz T, Fox PF, Kelly AL (2004a) Properties of casein micelles in high pressure-treated bovine milk. Food Chem 87:103–110CrossRefGoogle Scholar
  14. Huppertz T, Fox PF, Grosman S, Kelly AL (2004b) Dissociation of caseins in high pressure-treated bovine milk. Int Dairy J 14:125–133CrossRefGoogle Scholar
  15. Keenan RD, Hubbard CD, Mayes DM, Tier CM (2003) Role of calcium phosphate in the high-pressure-induced gelation of milk. In: Food colloids-biopolymers and materials. The Royal Society of Chemistry, Cambridge pp 109–118Google Scholar
  16. McMahon DJ, McManus WR (1998) Rethinking casein micelle structure using electron microscopy. J Dairy Sci 81:2985–2993CrossRefGoogle Scholar
  17. Mozhaev V, Heremans K, Frank J, Masson P, Balny C (1996) Proteins: Structure Function, and Genetics 24:81–91Google Scholar
  18. Needs EC, Stenning RA, Gill AL, Ferragut V, Rich GT (2000) High pressure treatment of milk: effects on casein micelle structure and on enzyme coagulation. J Dairy Res 67:31–42CrossRefGoogle Scholar
  19. Provencher SW (1982) Comput Phys Comm 27:213–229Google Scholar
  20. Regnault S, Thiebaud M, Dumay E, Cheftel JC (2004) Pressurisation of raw skim milk and of a dispersion of phospho-caseinate at 9°C or 20°C: effects on casein micelle size distribution. Int Dairy J 14:55–68CrossRefGoogle Scholar
  21. Tolkach A, Kulozik U (2005) Fractionation of whey proteins and caseino-macropeptide by means of enzymatic cross-linking and membrane separation techniques. J Food Eng 67:13–20CrossRefGoogle Scholar
  22. Walstra P, Jenness R (1984) Dairy chemistry and physics. Wiley, New YorkGoogle Scholar
  23. Walstra P (1999) Casein sub-micelles: do they exist? Int Dairy J 9:189–192CrossRefGoogle Scholar

Copyright information

© EBSA 2006

Authors and Affiliations

  • Ronald Gebhardt
    • 1
  • Wolfgang Doster
    • 1
  • Josef Friedrich
    • 2
  • Ulrich Kulozik
    • 3
  1. 1.Physik-Department E 13Technische Universität MünchenGarchingGermany
  2. 2.Physik-Department E14 and Lehrstuhl für Physik WeihenstephanTechnische Universität MünchenFreisingGermany
  3. 3.Lehrstuhl für Lebensmittel-Verfahrenstechnik und MolkereitechnologieTechnische Universität MünchenFreisingGermany

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