Quantification of _s1-Casein in Goat Milk from French-Alpine and Anglo-Nubian Breeds Using Reversed-Phase High Performance Liquid Chromatography

¹ Cooperative Agricultural Research Center, Prairie View A&M University, Prairie View, TX 77448
² Eastern Regional Research Center, Agricultural Research Service, USDA, 600 East Mermaid Lane, Philadelphia, PA 19118

Samples of isoelectrically precipitated goat casein from the milks of French-Alpine and Anglo-Nubian breeds were separated into four components in a single run by reversed-phase HPLC. The proportion of _s1-casein thus resolved was determined quantitatively. The method uses a reversed-phase C-4 column and a linear gradient from 30 to 50% acetonitrile in 30 min with trifluoroacetic acid constant at .1%. Sodium dodecyl sulfate-PAGE was carried out to establish the identity of the isolated components. By a comparison with previously published results for caprine and bovine milk caseins, the four peaks were identified as -, _s2-, _s1-, and ß- casein.

Quantitative variations in the chromatographically resolved _s1-casein fraction of goat milk were evident. Some individual goat milks contained high levels of _s1-casein (2.70 g/L), but others contained significantly low levels (.12 g/ L). There was no statistical difference in the overall means between breeds in _s1-casein composition, but cluster analysis statistics showed three distinct categories of _s1-producers: high, medium, and low. Interestingly, 6 of 15 French-Alpine goats and only one Anglo-Nubian goat fell into the "low" producer category (.38 ± .2 g/L). Thus, expression of the _s1- component may be genetically regulated but may not be a breed-specific trait.

Key Words: reversed-phase • high performance liquid chromatography • casein • caprine

Submitted on December 26, 1990
Accepted on March 7, 1991

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