Influence de la mammite sur les propriétés technologiques du lait et sur la qualité des produits laitiers

Abstract - The aim of this study was to collect bibliographical data concerning the influence of mastitis on milk composition and in connection with production and quality of dairy products.
Although the presence of antibiotics in mastitis milk, due to intense use in controlling the disease is a very important aspect of the problem, it is not discussed here.
Disturbances in the conversion of blood components into normal milk components seems to be generally accepted.
The opinions on the influence of udder inflammation on milk composition are sometimes rather divergent. This is not surprising as mastitis milk can differ from normal milk in a lesser up to a higher extent. Besides, various criteria are used for the appreciation of mastitis milk. Moreover, determinations of certain substances have not always been executed by the same methods.
Mastitis milk is not a good culture medium for certain lactic acid bacterial strains for reason of its high cell content and / or the altered chemical composition of the milk.
In cheese manufacture the coagulation time can be lengthened, the firmness of the curd can be diminished and the whey-running can be influenced.
Mastitis milk has a lesser heat stability than normal milk.
We may accept that the udder-secretion from animals suffering from acute mastitis is not delivered to the dairies. All other mastitis milk however is delivered. Il is mainly the influence of this milk on the quality which will be discussed.
High demands may and must be made upon marketing milk. A great effort must certainly be made in order to limit the admixture of mastitis milk.
The influence of mastitis milk on the quality of cheese is connected to the nature of the milk used, the cheese type and the technique employed in manufacture. Our present knowledge is partially based on experience and not on research. In recent years little has been published concerning the influence of mastitis milk on the quality of cheese and the results are based on a restraint number of trials only. From these researches it appears that a possible diminution of quality must be taken into account.
The slower coagulation with rennet of mastitis milk is the factor which influences mostly the quality of the cheese, therefore it seems to be advisable that research workers should look out for a modified manufacturing technique for some types of cheese, to compensate for this.
Even though recent research is limited and only a small number of experimental trials is discussed, there are indications that the quality of butter, manufactured from mastitis cream may be lowered.
Mastitis milk may interfere in the rather difficult problem of heat stability of milk and influence the manufacture of evaporated milk. There are indications that mastitis milk causes difficulties in the preparation of evap.
How bulk milk, containing mastitis milk, will react in the manufacture of dairy products depends on the percentage of mastitis milk and the nature of the chemical alteration of this milk.
It can be taken for granted that when milk is heated to normal pasteurisation temperature or higher, the bacteria which are pathogenic to humans or which create difficulties in the manufacture of dairy products are killed. If not thus heat-treated, then the bacteria in the mastitis milk get into these products and can give rise to difficulties in the manufacture as well as causing illnesses in man.
As conclusion we must point out that as far as the manufacture of dairy products from mastitis milk is concerned, even though relatively little research has recently been carried out, account must however be taken of a detrimental influence on the quality.
If not too large a quantity of mastitis milk is added, it may be assumed that no problems, or at any rate only very few problems, will arise in manufacturing bulk milk.
More research about the influence of mastitis milk on the technological practicability of the milk and on the quality of the dairy products is strongly desirable