Effect of protein, nonprotein-soluble components, and lactose concentrations on the irreversible thermal denaturation of beta-lactoglobulin and alpha-lactalbumin in skim milk.
The effect of protein, nonprotein-soluble components, and lactose concentrations on the irreversible denaturation of beta-lactoglobulin (beta-LG) and alpha-lactalbumin (alpha-LA) in reconstituted skim milk samples was studied over a wide temperature range (75-100 degrees C). The irreversible thermal denaturation of beta-LG had a reaction order of 1.5 and that of alpha-LA had a reaction order of 1.0 in all systems and under all conditions. The rates of irreversible denaturation of beta-LG and alpha-LA were markedly dependent upon the composition of the milk. At all temperatures, the irreversible denaturations of beta-LG and alpha-LA were enhanced at a higher protein concentration and were retarded when the nonprotein-soluble components and lactose concentrations were increased. The effects of increasing the concentrations of lactose and nonprotein-soluble components were interpreted using the preferential hydration theory and allowed for the interpretation of the changes in the denaturations of beta-LG and alpha-LA when the milk total solids concentration was increased.
Anema
Skelte G
SG
Lehrstuhl für Chemie der Biopolymere, Technische Universität München, 85350 Freising, Germany. skelte.anema@fonterra.com
Lee
Siew Kim
SK
Klostermeyer
Henning
H
D000818:Animals; D005223:Fats / Q000032:analysis; D006358:Hot Temperature; D007768:Lactalbumin / Q000032:analysis / Q000737:chemistry*; D007782:Lactoglobulins / Q000032:analysis / Q000737:chemistry*; D007785:Lactose / Q000032:analysis*; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis*; D011489:Protein Denaturation; D012995:Solubility; D013816:Thermodynamics
D005223:Fats; D007782:Lactoglobulins; D008894:Milk Proteins; D007768:Lactalbumin; D007785:Lactose