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Published on: December 16, 2015
Casein content of human milk
The American Journal of Clinical Nutrition
|January 1, 1985
Summary
Estimating human milk casein content is crucial for infant formula. Sedimentation by ultracentrifugation provided the most reliable casein measurement, with implications for infant nutrition guidelines.
Area of Science:
- Biochemistry
- Human Milk Composition
- Nutritional Science
Background:
- Accurate quantification of casein in human milk is essential for infant nutrition.
- Existing methods for casein estimation vary in reliability and accuracy.
- Understanding casein's role in nutrient binding is vital for infant formula development.
Purpose of the Study:
- To evaluate and compare three distinct methods for estimating casein content in mature human milk.
- To determine the most accurate method for casein quantification.
- To assess the binding of trace elements and minerals to casein.
Main Methods:
- Isoelectric precipitation with washing and correction for co-precipitating proteins.
- Sedimentation by ultracentrifugation.
- Indirect analysis via major whey protein content subtraction.
- Gel electrophoresis and amino acid analysis for result confirmation.
Main Results:
- Casein content (mg/ml) in mature human milk: 2.33 ± 1.69 (isoelectric precipitation), 1.80 ± 0.48 (sedimentation), and 2.96 ± 1.08 (indirect).
- A probable nitrogen partition in breast milk is casein N: whey protein N: non-protein N at 20:50:30.
- Trace elements (Ca, Mg, Zn, Cu, Fe) are bound to casein, with ultracentrifugation revealing specific percentages bound.
Conclusions:
- Sedimentation by ultracentrifugation appears to be the most reliable method for casein estimation in human milk.
- Isoelectric precipitation can lead to redistribution of bound trace elements.
- Findings impact the protein ratio guidelines for infant formula manufacturing and infant nutrition.
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