Revea Ling Casein Micelle Dispersion under Various Ranges of Nacl: Evolution of Particles Size and Structure

Dispersions of casein micelles (CM) were studied at a constant protein concentration of 5 wt % in high NaCl environment ranging from 0% to 12% by Dynamic light scattering (DLS) and Fourier Transform Infrared (FTIR). The rehydration profiles obtained were interpreted in term of wetting, swelling and dispersion stages by using a turbidity method. Two behaviours were observed depending on the salt concentration. The first behaviour (low salt concentration) presents a typical rehydration profile with a significant change between 3 and 6% NaCl indicating quick wetting, swelling and long dispersion stage. On the opposite, the dispersion stage of the second behaviour (high salt concentration) was significantly shortened indicating a strong modification of the protein backbone. A salt increase result to a destabilization of the micelle and the formation of mini-micelles more or less aggregated indicating an average micelles size ranging from 100 to 200 nm. For the first time, the estimations of secondary structural elements (irregular, ß-sheet, α-helix and turn) by the Amide III assignments were correlated with results from Amide I.




References:
[1] L. Sawyer, P. N. Barlow, M. J. Boland, L. K. Creamer, H. Denton, P. J.
B . Edwards, C. Holt, G. B. Jameson, G. Kontopidis, G. E. Norris, S.
Uhrinova, and S. Y. Wu, Milk protein structure - What can it tell the
dairy industry╦Ø╦Ø? Int. Dairy J. 12: 299-310, 2002.
[2] P. Walstra, Casein sub-micelles: Do they exist╦Ø╦Ø? Int. Dairy J. 9: 189-
192, 1999.
[3] H. E. Swaisgood, Characteristics of milk In Food Chemistry, 3rd ed.;
Fenneman, O. R., Ed.Marcel Dekker, Inc.: New York: pp 841-878, 1996.
[4] M. H. Famelart, Y. Le Graet, and K. Raulot, Casein micelle
dispersions into water, NaCl and CaCl 2: Physicochemical
characteristics of micelles and rennet coagulation Int. Dairy J. 9: 293-
297.
[5] F. Gaucheron, Y. Le Graet, M. Piot, and E. Boyaval, Determination of
anions of milk by ion chromatography Lait, 76: 433-443, 1996.
[6] T. F. Kumosinski, and J. J. Unruh, Quantitation of the global
secondary structure of globular proteins by FTIR spectroscopy:
Comparison with X-ray crystallographic structure Talanta, 43: 199-
219, 1996.
[7] D. M. Curley, T. F. Kumosinski, J. J. Unruh, and H. M. Farrell Jr,
Changes in the Secondary Structure of Bovine Casein by Fourier
Transform Infrared Spectroscopy: Effects of Calcium and
Temperature J. Dairy Sci. 81: 3154-3162, 1998.
[8] D. M. Byler and H. Susi, Examination of the secondary structure of
proteins by deconvolved FTIR spectra Biopolymers, 25: 469-487,
1986.
[9] S. Cai, and B. R. Singh, Identification of β-turn and random coil amide
III infrared bands for secondary structure estimation of proteins
Biophys.Chem. 80: 7-20, 1999.
[10] A. O. Karlsson, R. Ipsen, and Y. Ardö, Observations of casein micelles
in skim milk concentrate by transmission electron microscopy LWT -
Food Sci. Tech. 40: 1102-1107, 2007.
[11] M. Philippe, Y. Le Graët, and F. Gaucheron, The effects of different
cations on the physicochemical characteristics of casein micelles Food
Chem. 90: 673-683, 2005.
[12] T. Huppertz and P. F. Fox, Effect of NaCl on some physico-chemical
properties of concentrated bovine milk Int. Dairy J. 16: 1142-1148,
2006.
[13] A. HadjSadok, A. Pitkowski, T. Nicolai, L. Benyahia, and N. M.
Mostefa, Characterisation of sodium caseinate as a function of ionic
strength, pH and temperature using static and dynamic light scattering
Food Hydrocolloid. 22: 1460-1466, 2008.
[14] C. Gaiani, S. Banon, and J. Scher, P. Schuck, and J. Hardy Use of a
turbidity sensor to characterize micellar casein powder rehydration:
Influence of some technological effects J. Dairy Sci. 88: 2700-2706,
2005.
[15] H.M. Farrell Jr, E. D. Wickham, J. J. Unruh, P. X. Qi, and P. D.
Hoagland, Secondary structural studies of bovine caseins: Temperature
dependence of β-casein structure as analyzed by circular dichroism and
FTIR spectroscopy and correlation with micellization Food
Hydrocolloid. 15: 341-354, 2001.
[16] C. Gaiani, J. Scher, J. J. Ehrhardt, M. Linder, P. Schuck, S. Desobry,
and S. Banon, Relationships between dairy powder surface
composition and wetting properties during storage: importance of
residual lipids J. Agr. Food Chem. 55: 6561-6567, 2007.
[17] R. Jost, Functional characteristics of dairy proteins Trends, Food Sci.
4: 283-288, 1993.
[18] P. Schuck, A. Davenel, F. Mariette, V. Briard, S. Méjean and M. Piot,
Rehydration of casein powders: Effects of added mineral salts and salt
addition methods on water transfer Int. Dairy J. 12: 51-57, 2002.
[19] C. Le Ray, J. L. Maubois, F. Gaucheron, G. Brulé, P. Pronnier, and F.
Garnier, Heat stability of reconstituted casein micelle dispersions:
Changes induced by salt addition Lait, 78: 375-390. 1998.
[20] M. B. Grufferty, and P. F. Fox, Effect of Added NaCl on Some
Physicochemical Properties of Milk Irish. J. Food Sci. Tec. 9: 1-9.
1985.
[21] D. S. Horne, and C. M. Davidson, The effect of environmental
conditions on the steric stabilization of casein micelles Colloid Polym.
Sci. 264: 727-734. 1986.
[22] S. Cai, and B. R. Singh, A Distinct Utility of the Amide III Infrared
Band for Secondary Structure Estimation of Aqueous Protein Solutions
Using Partial Least Squares Methods Biochemistry, 43: 2541-2549.
2004.
[23] R. Hussain, C. Gaiani, L. Aberkane, and J. Scher, Characterization of
high-milk-protein powders upon rehydration under various salt
concentrations J. Dairy Sci. 2010, in press.
[24] P. Walstra, On the stability of casein micelles J. Dairy Sci. 73: 1965-
1979. 1990.
[25] M. J. Jonkman, P. Walstra, M. A. J. S. Van Boekel and D. J. Cebula,
Behaviour of casein micelles at conditions comparable to those in ice
cream Int. Dairy J. 9: 201-205. 1999.