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Rangées de graines.. © INRA, Elena Schweitzer © Fotolia

Our results

  1. Introduction
  2. Research and Innovation 2018 - For Food and Biobased Products
  3. Dry-cured ham: a process simulator can now define routes of manufacture that yield lower-salt products
  4. The way in which proteins aggregate when heated may change their sensitising potency
  5. Enhancing the viability of spray-dried probiotic bacteria by stimulating their stress tolerance
  6. Human milk digestion in the preterm infant: impact of technological treatments
  7. Research & Innovation 2017 - For Food and Biobased Products
  8. To stick or not to stick? Pulling pili sheds new light on biofilm formation
  9. When biopolymers selfassemble: a balance between energy and entropy.
  10. Mimicking the gastrointestinal digestion in a lab-on-a-chip:the microdigester
  11. How a milk droplet becomes a powder grain
  12. Research & Innovation 2016 - For Food and Bioproducts
  13. A new process for the biorefining of plants
  14. Under the UV light : the bacterial membrane
  15. Reverse engineering or how to rebuild ... bread!
  16. Green Chemistry: a step towards lipid production in yeast
  17. Individually designed neo-enzymes for antibacterial vaccines
  18. Multi-scale mechanical modelling: from the nanometric scale to the macroscopic properties of bread crumb
  19. Minimill: 500 g to assess the milling value of soft wheats
  20. Microbial production of lipids for energy or chemical purposes
  21. The discrete role of ferulic acid in the assembly of lignified cell wall
  22. Eco-design of composites made from wood co-products
  23. Analysis of volatile compounds enables the authentication of a poultry production system
  24. Nanoparticles as capping agents for biopolymers microscopy
  25. Pasteurisation, UHT, microfiltration...All the processes don't affect the nutritional quality of milk in the same way
  26. Integration of expert knowledge applied to cheese ripening
  27. Controlling cheese mass loss during ripening
  28. The shape memory of starch
  29. Research & Innovation 2015 - For Food & Biobased Products
  30. Behaviour of casein micelles during milk filtering operations
  31. Overaccumulation of lipids by the yeast S. cerevisiae for the production of biokerosine
  32. Sequential ventilation in cheese ripening rooms: 50% electrical energy savings
  33. An innovative process to extract bioactive compounds from wheat
  34. Diffusion weighted MRI: a generic tool for the microimaging of lipids in food matrices
  35. Characterization of a major gene of anthocyanin biosynthesis in grape berry
  36. New enzyme activity detectors made from semi-reflective biopolymer nanolayers
  37. Improving our knowledge about the structure of the casein micelle
  38. Heating milk seems to favour the development of allergy in infants
  39. Fun with Shape
  40. Using volatile metabolites in meat products to detect livestock contamination by environmental micropollutants
  41. SensinMouth, when taste makes sense
  42. A decision support system for the fresh fruit and vegetable chain based on a knowledge engineering approach
  43. SOLEIL casts light on the 3D structure of proteins responsible for the stabilisation of storage lipids in oilseed plants
  44. A close-up view of the multi-scale protein assembly process
  45. Controlling the drying of infant dairy products by taking water-constituent interactions into account
  46. Polysccharide nanocrystals to stabilise pickering emulsions
  47. Discovery of new degradative enzymes of plant polysaccharides in the human intestinal microbiome
  48. A durum wheat flour adapted for the production of traditional baguettes
  49. Virtual modelling to guide the construction of « tailored-made » enzymes
  50. How far can we reduce the salt content of cooked meat products?
  51. Diffusion of organic substances in polymer materials: beyond existing scaling laws
  52. Smart Foams : various ways to destroy foams on demand !
  53. Dates, rich in tannins and yet neither bitter nor astringent
  54. Sodium content reduction in food
  55. Research & Innovation 2014

Improving our knowledge about the structure of the casein micelle

The casein micelle, the main protein component of milk (80% of milk proteins), is undoubtedly the natural colloidal object that we encounter the most frequently in our everyday life.

Updated on 06/17/2013
Published on 06/05/2013

Discovering the construction and transformation mechanisms of the casein micelle in order to understand its dynamics   

This protein aggregate, comparable to a sphere of a hundred nanometres in diameter, has been studied for the past thirty years using physico-chemical methods. However, its structure and thus its molecular and supramolecular organisation, are still poorly established. This lack of knowledge is a major conceptual obstacle for understanding and therefore controlling its functionalities. In fact, the casein micelle plays a key role in many transformation processes in the food industry.

A better understanding of casein micelle structure  

To understand the micellar dynamics and organisation, we study the mechanisms of transport and construction of the micelle in the secretion pathway since these two processes are very closely interrelated. Our approach is unique in that we study these phenomena in situ in the mammary epithelial cell by exploiting the spatio-temporal aspect of micelle formation. The primary steps in the formation of the casein micelle are studied in vesicles derived from the rough endoplasmic reticulum, prepared from mammary tissues of rats or goats. These experiments reveal for the first time the existence of a form of alpha-S1 casein associated with the membrane in the endoplasmic reticulum and in the more distal compartments of the secretory pathway of mammary epithelial cells. Our data suggest that alpha-S1 casein, essential to the efficient export of other caseins from the endoplasmic reticulum to the Golgi apparatus, plays a key role in the first stages of the biogenesis of casein micelle and in the transport of caseins in the secretory pathway.

Through an approach that uses concentration by osmotic stress, a technique derived from "soft matter" physics, we showed that the micelle adopts a succession of behaviours typical of certain "model" colloids when the concentration is increased: hard sphere, "adhesive" sphere, followed by a "soft and deformable" colloid.  These results are directly applicable, through the knowledge of the concentration at the liquid-gel transition, for example.  As a follow-up to this research, we explored the internal structure of the casein micelle by following its evolution  during osmotic compression, using small angle x-ray scattering. During these manipulations, the physico-chemical environment of the micelle was unchanged, with the result that only its response to a mechanical stress was followed up.
The results obtained are particularly original and informative.  They suggest that the micelle is a heterogeneous material consisting of dense regions that resist compression, and "soft" regions or voids that contract or cave in when the micelle is deformed (see illustration).  This representation of a sponge-like casein micelle differs from existing models and is a major advance from the fundamental point of view.    
structrure of the caseine micelle under osmotic compression

Structure de la micelle de caséine sous compression osmotique. © INRA
Structure de la micelle de caséine sous compression osmotique © INRA

Illustration: Structure of the casein micelle under osmotic compression: (A) SAXS spectra of the micelle at different casein concentrations.  These spectra reveal three "oscillations", or characteristic distances, that correspond to the three levels of the internal structure of the micelle.  (B) Representation of the internal structure: a sponge-like micelle with three structural levels.   

Elucidating the structure of the casein micelle to control processes   

Determining the role of alpha-S1 casein in the transport of caseins in the secretory pathway as well as in the formation of the casein micelle, and identifying the mechanisms responsible for the establishment and secretion of this supramolecular structure will allow us to better understand and, therefore, control casein micelle production by the mammary epithelial cell and the functionalities associated with it  
To control these processes, it is of utmost importance to elucidate casein micelle structure and to understand how this structure and the overall behaviour of the micelle are affected during transformation and concentration operations.  In the long run and in terms of applications, improving our knowledge of casein micelle structure will make it possible to advance on many points related to the manipulation and use of this biological object in different areas: control of transformation processes, encapsulation and controlled release of target compounds, etc.    


This work was carried out with the collaboration of B. Cabane (ESPCI, UMR7636 PMMH) and the Inra division for Animal Physiology: Eric Chanat, Annabelle Le Parc, INRA, UR1196 Génomique et Physiologie de la Lactation, Domaine de Vilvert, F-78350 Jouy-en-Josas.


See also

  • A. Le Parc, J. Léonil, E. Chanat. AlphaS1-casein, which is essential for efficient ER-to-Golgi transport, is also present in a tightly membrane-associated form. BMC Cell Biology 2010, 11:65
  • http://www.biomedcentral.com/1471-2121/11/65. doi:10.1186/1471-2121-11-65
  • A. Bouchoux, P.-E. Cayemitte,J. J., G. Gésan-Guiziou, B. Cabane, Biophys. J., vol.96, p.693, 2009
  • A. Bouchoux, B. Debbou, G. Gésan-Guiziou, M.-H. Famelart, J.-L. Doublier, B. Cabane, J. Chem. Phys., vol.131, p.165106, 2009
  • A. Bouchoux, G. Gésan-Guiziou, J. Perez, B. Cabane, Biophys. J., vol.99, p.3754, 2010
  • Behaviour of casein micelles during milk filtering operations
  • What's new in the Milky Way