Effect of Heat Treatment on Whey Proteins Denaturation in the Presence and Absence of Lactose

Jasim M.S. Al-Saadi
Food Science Department, Technical College of Agriculture, Halabja, Sulimmania

The effect of lactose on denaturation of whey proteins was investigated in cow
milk, with and without lactose, heated at different temperatures ranged of (65-95)°C for
30 min. Compared with the milk without, the milk containing lactose showed a smaller
increase in pH values and a higher concentration of whey proteins. Whey proteins
percentage in milk samples with and without lactose heated at (65,70,75 ,80,85,90 and
95) °C for 30 min were(90.38,88,86.16 , 67.9,44,23,23.5 and 23.2%) and (82.85,75, 71.14 ,
44.18,25.92,20.52 and 20%) respectively. It was concluded that heating cause formation
new band located below β-Lg band in whey samples of both milk ,with and without
lactose , and the intensity of this band increased with increment of heating temperatures
and heating time.

Keywords: milk proteins, heat treatment, whey proteins , denaturation


[1] H.S. Singh, "Heat-induced interactions of proteins in milk. Protein and fat globule
modifications" IDF seminar, special issue 9303. 191, (1993).
[2] D. W. S. Wong, W. M. Camirand and A. E. Pavlath, "Structures and Functionalities of
Milk Proteins" Critical Reviews in Food Science and Nutrition, 36 , pp.807-844, (1996).
[3] H.E. Swaisgood, " Review and update of casein chemistry" Journal of Dairy Science, 76,
[4] A. J. R. Law, D. S. Horne, J. M. Banks and J. Leaver "Heat induced changes in the whey
proteins and caseins" Milchwissenshaft, 49, pp.125-129, (1994).
[5] H. D. Jang and H. F. Swaisgood " Disuiphide bond formation between thermally
denatured β-lactoglobulin and k-casein micelles" Journal of Dairy Science, 73, pp.900-904,(1990).
[6] P. F. Fox, " Advanced dairy chemistry. I. Proteins" Applied Science Publishers , London ,(1992).
[7] A. R. Hill, " The β-lactoglobulin-k-casein complex" Canadian Institute of Food Science
and Technology Journal, 22, pp.120-123, (1989).
[8] M. Corredig and D. Dalgleish, " The mechanisms of the heat-induced interaction of whey
proteins with casein micelles in milk" International Dairy Journal, 9, pp.233-236,(1999).
[9] S. G. Anema and Y. Li, "Effect of pH on the association of denatured whey proteins with
the casein micelles in heated reconstituted skim milk" Journal of Agricultural and Food
Chemistry, 51, pp.1640−1646 ,(2003).
[10] J. M. S. Al-Saadi , A. M. Easa and H.C. Deeth "Effect of lactose on cross-linking of milk
proteins during heat treatments" International Journal of Dairy Technology, 63 ,pp. 1-6, (2013).
[11] R. Jenness and J. Koops" Preparation and properties of a salt solution which simulates
milk ultra-filtrate" The Netherlands Milk and Dairy Journal, 3,pp. 153–164,(1962).
[12] A. L, Kelly and J. Foley " Proteolysis and storage stability of UHT milk as influenced by
milk plasmin activity, plasmin/β-lactoglobulin complexation, plasminogen activation and
somatic cell count" International Dairy Journal ,7, pp.411–420,(1997).
[13] Association of Official Analytical Chemists "Official methods of analysis", 13th ed. pp
[14] U. K. Laemmli "Cleavage of structural proteins during the assembly of the head of
bacteriophage T4" Nature, 227 ,pp.680-685,(1970).
[15] A.T. Andrews "Properties of aseptically packed ultra-high-temperature milk. III.
Formation of polymerized protein during storage at various temperatures" Journal of
Dairy Research, 42,pp. 89-99,(1975).
[16] N. Venkatachalam, D. J. McMahon and P. A. Savello "Role of protein and lactose
interactions in the age gelation of ultra-high-temperature processed concentrated skim
milk" Journal of Dairy Science,76,pp.1882-1894,(1993).
[17] H.T. Wright" Nonenzymatic deamidation of asparaginyl and glutaminyl residues in
proteins" Critical Reviews in Biochemistry and Molecular Biology, 26,pp. 1-52,(1991).
[18] D. G. Dalgleish and J. A. Hunt" Protein-protein interactions in food materials"In
Ingredient Inter-actions. Effects on Food Quality (Ed. A.G. Gaonkar). Marcel Dekker,
New York, pp. 199-233,(1995 ).
[19] M. van Boekel "Heat-induced deamidation, dephosphorylation and breakdown of
caseinate " International Dairy Journal, 9,pp. 237-241,(1999).
[20] L. Pellegrino, M. van Boekel, H. Gruppen, P. Resmini and M. A. Pagani " Heat-induced
aggregation and covalent linkages in β-casein model systems" International Dairy
Journal, 9,pp. 255-260,(1999).
[21] J. M. S. Al-Saadi and C. H. Deeth "Cross-linking of proteins in UHT milk during
storage at different temperatures" Australian Journal of Dairy Technology, 63,pp. 93-99,(2008).