Molecular weight and size distribution of bovine milk casein micelles

SummaryWhole milk was concentrated by ultrafiltration in a plant causing some homogenization of the fat. Comparisons were made with milk concentrated in a plant causing little homogenization and with milk homogenized conventionally. None of the processes appreciably affected the casein micelle size distribution. On rennet treatment of homogenized milk, casein micelle aggregation occurred more slowly, the protein network in the curd was less coarse and the rate of whey loss was reduced, compared with non-homogenized milk at the same concentration. In using concentrated milks for cheesemaking homogenization improved the composition of Cheddar cheese, because of increased fat and moisture retention, but curd fusion was poorer. Some aspects of the texture of the mature cheeses were improved, but the free fatty acid levels were higher. Values for the firmness of curds, formed from milks processed in different ways, did not relate to the extent of aggregation of the casein micelles. It is suggested that the complete cheesemaking process is driven by the tendency of the casein to aggregate.

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Determination of molecular weight of a purified fraction of colloidal calcium phosphate derived from the casein micelles of bovine milk

Journal of Dairy Science ◽

10.3168/jds.2010-3762 ◽

2011 ◽

Vol 94 (7) ◽

pp. 3250-3261 ◽

Cited By ~ 20

Author(s):

J. Choi ◽

D.S. Horne ◽

J.A. Lucey

Keyword(s):

Molecular Weight ◽

Calcium Phosphate ◽

Bovine Milk ◽

Casein Micelles ◽

Colloidal Calcium Phosphate

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Changes in the Distribution of Cadmium and Lead in Human and Bovine Milk Induced by Heating or Freezing

Journal of Food Protection ◽

10.4315/0362-028x-59.1.46 ◽

1996 ◽

Vol 59 (1) ◽

pp. 46-50 ◽

Cited By ~ 3

Author(s):

LUIS MATA ◽

LOURDES SANCHEZ ◽

PILAR PUYOL ◽

MIGUEL CALVO

Keyword(s):

Molecular Weight ◽

Whey Proteins ◽

Bovine Milk ◽

Marked Change ◽

Weight Fraction ◽

Low Molecular Weight ◽

Casein Micelles ◽

Fat Fraction ◽

Cadmium And Lead ◽

Formation Of Complexes

The percentage of cadmium or lead present in the fat fraction of bovine milk is not affected by heating or freezing. In human skimmed milk, cadmium is mainly associated with a fraction with molecular weight lower than 10,000. Storage at −20°C for 10 days does not have any effect on the distribution of cadmium when milk is incubated with this metal before freezing. This treatment causes only a small increase in the amount of cadmium associated with the low molecular weight fraction when the metal is added after freezing. In bovine milk, 64% of cadmium is associated with a fraction with molecular weight above 70,000. Freezing causes a 37% decrease of the cadmium present in this fraction when the metal is added after thawing. When bovine milk was incubated with cadmium before freezing there was not a marked change in its distribution as when added after thawing. Heating at 63°C for 30 min caused a slight decrease in the amount of cadmium present in the casein fraction. The distribution change of cadmium after freezing or heating is probably due to the formation of complexes between the whey proteins and the metal, or to the disaggregation of the cadmium bound to casein micelles. Lead is mainly associated with caseins in bovine and human milk. No significant changes were caused by freezing or heating in the distribution of lead in human and bovine milk.

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Size distribution and average size parameters of casein micelles determined by electron microscopy in bovine milk between pH 5·5 and 6·7. A comparison of several evaluation methods

Journal of Dairy Research ◽

10.1017/s0022029900029873 ◽

1991 ◽

Vol 58 (3) ◽

pp. 299-312 ◽

Cited By ~ 4

Author(s):

Henk J. Vreeman ◽

Bas W. van Markwijk ◽

Paula Both

Keyword(s):

Electron Microscopy ◽

Size Distribution ◽

Bovine Milk ◽

Three Dimensional ◽

Skim Milk ◽

Two Dimensional ◽

Casein Micelles ◽

Milk Samples ◽

Dimensional Distribution ◽

Average Size

SummaryThe conversion of the two-dimensional size distribution of casein micelles, observed by electron microscopy in a plane section, to the three dimensional distribution is discussed and the average size parameters evaluated by several methods are compared. It is shown that parameters containing the −1 moment of the two-dimensional distribution, i.e. Dn, the number of micelles per unit volume and the width of the size distribution, are sometimes uncertain. The occurrence of negative numbers in some of the classes of the distribution is discussed and remedies are suggested. Sections were made by freeze-fracturing skim milk samples; the pH of the milk was between 5·5 and 6·7.

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