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Research article2013Peer reviewedOpen access

Casein Breakdown in Bovine Milk by a Field Strain of Staphylococcus aureus

Johansson, Monika; Åkerstedt, Maria; Li, Shengjie; Zamaratskaia, Galia; Sternesjö Lundh, Åse

Abstract

The objectives of this study were to establish the proteolytic effects of Staphylococcus aureus during mastitis on economically important milk proteins. Concentrations of milk proteins were determined by capillary electrophoresis in an experimental model using a field strain of S. aureus. The pathogen was inoculated into bacteria-free control milk to imitate proteolysis caused by the pathogen in the mammary gland between milkings. Milk content of caseins (CN) alpha(S1), alpha(S2), kappa, beta(A1), and beta(A2) and whey proteins alpha-lactalbumin and beta-lactoglobulin were analyzed initially and after 6 h of incubation. After 6 h, the overall CN content was significantly reduced (21%) in milk inoculated with S. aureus compared with the bacteria-free control milk. S. aureus significantly lowered concentration of alpha(S1)-CN (2.5%), beta(A1)-CN (3%), and beta(A2)-CN (5%). S. aureus also hydrolyzed kappa-CN into para-kappa-CN, with significant reduction of kappa-CN (7.4%) as a consequence.

Published in

Journal of Food Protection
2013, Volume: 76, number: 9, pages: 1638-1642
Publisher: INT ASSOC FOOD PROTECTION