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Detecting β-Casein Variation in Bovine Milk

Unit of Biotechnology, Department of Molecular and Translational Medicine, University of Brescia, Brescia 25123, Italy
Author to whom correspondence should be addressed.
Academic Editor: Fernando Albericio
Molecules 2016, 21(2), 141;
Received: 25 November 2015 / Revised: 30 December 2015 / Accepted: 18 January 2016 / Published: 25 January 2016
(This article belongs to the Section Natural Products Chemistry)
PDF [1336 KB, uploaded 25 January 2016]


In bovine species, β-casein (β-CN) is characterized by genetic polymorphism. The two most common protein variants are β-CN A2 (the original one) and A1, differing from A2 for one amino acid substitution (Pro67 to His67). Several bioactive peptides affecting milk nutritional properties can originate from β-CN. Among them, β-casomorphin-7 (BCM7) ranging from amino acid 60 to 66 can be released more easily from β-CN variants carrying His67 (A1 type) instead of Pro67 (A2 type). Nowadays, “A2 milk” is produced in different countries claiming its potential benefits in human health. The aim of this study was to further develop and apply an isoelectric focusing electrophoresis (IEF) method to bulk and individual milk samples in order to improve its use for β-CN studies. We succeeded in identifying A2 milk samples correctly and quantifying the percentage of A2, A1, and B variants in bulk samples not derived from A2 milk as well as in individual milk samples. The method allows us to quantify the relative proportion of β-CN variants in whole milk without eliminating whey protein by acid or enzymatic precipitation of caseins. The aim of this study was also to study the different behavior of β-CN and β-lactoglobulin (β-LG) in the presence of trichloroacetic acid (TCA). The higher sensitivity of β-CN to TCA allows quantifying β-CN variants after TCA fixation because β-LG is not visible. Monitoring β-CN variation in cattle breeds is important in order to maintain a certain balance between Pro67 and His67 in dairy products. Overall, the debate between A1 and A2 milk needs further investigation. View Full-Text
Keywords: bovine milk; β-casein; bioactive peptide; isoelectric focusing bovine milk; β-casein; bioactive peptide; isoelectric focusing

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Caroli, A.M.; Savino, S.; Bulgari, O.; Monti, E. Detecting β-Casein Variation in Bovine Milk. Molecules 2016, 21, 141.

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