Short communication: Effect of subclinical mastitis on proteolysis in ovine milk
2011
Marti-de Olives, A. | Le Roux, Yves | Rubert-Aleman, J. | Peris, C. | Molina, M. P. | Universidad Miguel Hernández [Elche] (UMH) | Unité de Recherches Animal et Fonctionnalités des Produits Animaux (URAFPA) ; Institut National de la Recherche Agronomique (INRA)-Université de Lorraine (UL) | Universitat Politècnica de València = Universitad Politecnica de Valencia = Polytechnic University of Valencia (UPV) | government of Valencia ("Generalitat Valenciana")
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Show more [+] Less [-]English. The aim of this work was to evaluate the effect of intramammary infection (IMI) on the endogenous proteolysis of milk. Four control checks were carried out in the half-udder milk of 10 ewes that acquired unilateral subclinical mastitis. Two of these checks were conducted before the infection was established and 2 after. Ten healthy ewes were tested as a control group. The presence of a subclinical IMI involved an increase of the products of casein hydrolysis, the proteose-peptone (p-p) fraction and minor (m) caseins, and a decrease of beta-casein. As a result, a significant increase in the proteolysis index (PI), calculated as the ratio of m-casein to the sum of caseins (alpha + beta + kappa), took place. a-Casein and K-casein were not significantly affected by IMI. Correlations confirmed the scenario: log(10) of somatic cell count (SCC) was positively correlated with p-p content and negatively with beta-casein, whereas log(10) SCC was not correlated with alpha-casein or kappa-casein. On the other hand, p-p content was positively correlated with m-casein and PI and negatively with beta-casein, but no correlation was detected between p-p content and alpha- or kappa-casein. Furthermore, between casein fractions, m-casein was only significantly correlated with beta-casein. These results suggest that use of indices of proteolysis of caseins such as p-p, m-casein, and PI, could be applied together with SCC to evaluate the cheese-making quality of milk.
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