Quantification of αs1-Casein in Goat Milk from French-Alpine and Anglo-Nubian Breeds Using Reversed-Phase High Performance Liquid Chromatography

Abstract

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 alpha 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 kappa-, alpha s2-, alpha s1-, and beta-casein. Quantitative variations in the chromatographically resolved alpha s1-casein fraction of goat milk were evident. Some individual goat milks contained high levels of alpha 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 alpha s1-casein composition, but cluster analysis statistics showed three distinct categories of alpha 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 alpha s1-component may be genetically regulated but may not be a breed-specific trait.

Importance of Goat Milk

“…s1 -casein. The latter is present in highly variable amounts depending on individual goats (Mora-Gutierrez et al, 1991). Proportions of "-casein and especially #-casein are higher in goat than in cow milk.…”

Cheese yield, casein fractions and major components of milk of Saanen and Anglo-Nubian dairy goats

“…Also, the αs1-CN shows the highest variability among the casein fractions of both breeds. This paper shows the content of casein fractions expressed in two different ways for more complete information, as some papers show levels of casein fractions in g/l (Mora- Gutierrez et al, 1991;Clark and Sherbon, 2000) or in relative percentage (Moatsou et al, 2004) between breeds, making it difficult to compare different studies. …”

Cross‐linking of bovine and caprine caseins by microbial transglutaminase and their use as microencapsulating agents for n‐3 fatty acids

“…One factor contributing to the differences in antioxidant activity of the bovine and caprine caseins in algae oil‐in‐water emulsions is the different profile of caseins (Mora‐Gutierrez et al ., ). Bovine and caprine caseins both contain the four main casein classes: α s1 ‐, α s2 ‐, β‐ and κ‐casein, but the level of α s1 ‐casein in caprine caseins isolated from the milks of American‐bred, French‐Alpine goats ranges from high to low (Mora‐Gutierrez et al ., ). The bovine and caprine caseins used in this study had different compositions in terms of α s1 ‐, α s2 ‐, β‐ and κ‐casein (Table ).…”

“…The samples of caprine milk were collected from individual French-Alpine animals, which were raised at the International Goat Research Center in Prairie View A&M University, TX, USA. The caprine milk caseins were selected based on yielding high and low levels of a s1 -casein as determined by reversed-phase high-performance liquid chromatography (RP-HPLC) (Mora-Gutierrez et al, 1991). Caseins were isolated from 2 L of fresh, uncooled milk to which phenylmethanesulphonyl fluoride (0.1 g L À1 ) was added immediately to retard proteolysis.…”

“…The enzyme mTG catalyses formation of intramolecular or intermolecular isopeptide linkage between glutamyl and lysyl residues within the target proteins (Christensen et al, 1996). Considering the variation in casein composition from caprine sources, the mTG cross-linking of caprine caseins may offer a better encapsulating material for n-3 fatty acids (Mora-Gutierrez et al, 1991). In this study, we evaluated the oxidative stability of algae oil microencapsulated by mTG-induced cross-linked caprine caseins with high and low levels of a s1 -casein.…”