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Crnadak, Ninoslava, 2012. Proteolysis in UHT milk due to Staphylococcus aureus. Second cycle, A2E. Uppsala: SLU, Dept. of Animal Nutrition and Management



The aim of this project was to analyse the effect of mastitis pathogen Staphylococcus (S.) aureus on proteolysis in UHT milk. S. aureus is one of the main pathogens that causes mastitis and reduces milk yield and quality which both leads to large economical losses. UHT milk was inoculated with four strains of S.aureus and then incubated at 37oC. Milk was sampled at six different time points (0, 0.5, 1, 2, 4, and 6 h). Samples were stored at -200C until analysis for protein separation by capillary electrophoresis (CE). CE was run for two strains (333 and 485) and electropherograms were obtained. Due to the quality of electropherograms only strain 485 was further evaluated for protein quantification. The level of milk proteins (caseins and whey proteins) was estimated for each sample by quantification of peak area. Data were statistically analysed using SAS ANOVA procedures. The lowest pH value of inoculated milk was 6.2, while pH of non-inoculated milk remained constant and was 6.7.
Bacterial growth in log phase reached levels of 8x10 8 and 8.7x10 8 colony forming units for strain 333 and 485, respectively. The overall casein content was reduced by up to 21% due to S. aureus.

Main title:Proteolysis in UHT milk due to Staphylococcus aureus
Authors:Crnadak, Ninoslava
Supervisor:Johansson, Monica
Examiner:Bertilsson, Jan
Series:Examensarbete / Sveriges lantbruksuniversitet, Institutionen för husdjurens utfodring och vård
Volume/Sequential designation:405
Year of Publication:2012
Level and depth descriptor:Second cycle, A2E
Student's programme affiliation:Other
Supervising department:(VH) > Dept. of Animal Nutrition and Management
Keywords:milk, protein, proteolysis
Permanent URL:
Subject. Use of subject categories until 2023-04-30.:Animal husbandry
Food contamination and toxicology
Deposited On:15 Jan 2014 14:08
Metadata Last Modified:15 Jan 2014 14:08

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