Milk somatic cells

Barbano D M, Rasmussen R R and Lynch J M (1991), Influence of milk somatic cell count and milk age on cheese yield , Journal of Dairy Science, 74, 369-388. 

Rainard, P, Ducelliez, M. and Poutrel, B. (1990), The contribution of mammary infections by coagulase-negative staphylococci to the herd bulk milk somatic cell count . Veterinary... 

Verdi, R. J., and Barbano, D. M. (1991). Properties of proteases from milk somatic cells and blood leukocytes. J. Dairy Sci. 74, 2077-2081. 

Fritsch, J. and Moraru, C. 1. (2007). Development and optimization of a carbon dioxide-aided cold microfiltration process for the physical removal of microorganisms and somatic cells from skim milk. /. Dairy Sci. 91, 3744-3760. 

Wieking, W. (2004). Removal of somatic cells from raw milk by state-of-the-art centrifugal technology. Bulletin of the International Dairy Federation 389, 45 7. 

Gunasekera,T. S. Veal, D. A. Attfleld,P. V. Potential for broad applications of flow cytometry and fluorescence techniques in microbiological and somatic cell analyses of milk. Int. J. Food Microbiol. 2003, 85, 269-279. 

The restricted shelf life of liquid milk continues to be a problem that is often more influenced by the type of milk being sold rather than the pasteurisation technique. The shelf life of processed milk is determined primarily by the quality of the raw milk from the dairy herd. Increasing cell counts in the milk and a higher concentration of free fatty acids, contribute to rancidity in both liquid milk and milk products. Janzen (1972) reported that the 0-14 day shelf life of pasteurised milk is influenced by the somatic cell concentration in the raw milk and found that after 14 days any observed changes in the flavour and stability of the milk were attributable to microbial activity during storage. 

Vitamin E supplementation has been shown to have positive effects on milk quality in a conventional commercial dairy herd. Milk obtained from cows that received supplemental vitamin E had lower somatic cell counts and plasmin concentrations than corresponding values in milk obtained from control cows. The reduction in plasmin as a result of vitamin E supplementation is very beneficial to the dairy industry because plasmin reduces the cheese-yielding capacity of milk, affects the coagulating properties of milk and its overall ability to withstand processing during cheesemaking (Politis et al., 2004). 

Janzen J J (1972), The effect of somatic cell concentration in the raw milk on the shelf-life of the processed product , Journal of Milk and Food Technology, 35, 112-114. 

Ma Y, Ryan C, Barbano D M, Galton D M, Rudan M A and Boor K J (2000), Effects of somatic cell count on quality and shelf-life of pasteurized milk fluid , Journal of Dairy Science, 83, 264-274. 

Politis I and Ng-Kwai-Hang K F (1988a), Effect of somatic cell counts and milk composition on cheese composition and coagulating properties of milk , Journal of Dairy Science, 71, 1711-1719. 

Sub-clinical mastitis, on the other hand, has no visible symptoms and can only be diagnosed with laboratory methods (Wendt et al., 1994) (see below). The diagnosis of sub-clinical mastitis depends on two parameters, the microbiological profile of sampled milk and the somatic cell count (Hamann and Fehlings, 2002). The different severity levels of mastitis and symptoms used in diagnosis are described in Table 11.3. 

Both clinical and sub-clinical mastitis are usually accompanied by an increase in the somatic cell count (SCC a measure of white blood cells (95%) such as macrophages, segmented neutrophil granulocytes or lymphocytes) in milk. SCCs above a certain level are an indication of immune-system activation and are used as an indicator of sub-clinical , latent or chronic udder infections/mastitis (Concha, 1986 Ostensson et al., 1988), which were shown to affect milk quality, composition and shelf life. Dairy companies therefore impose SCC thresholds or reduce payments to farmers if certain thresholds are exceeded (Hamann, 2001 Urech et al., 1999). 

Bartlett, P.C., Miller, G.Y., Anderson, C.R. and Kirk, J.H. (1990), Milk production and somatic cell count in Michigan dairy herds . Journal of Dairy Science, Oct, 2794-2800. 

Hamann, J. (2001), Relationships between somatic cell count and milk composition, in Proceedings of the IDF World Summit, Auckland/New Zealand. 

Hamann, J. and Gyodi, P. (1994), Effects on milk yield, somatic cell count and milk conductivity of short-term, non-milking of lactating quarters of cows . Journal of Dairy Research, 61, 317-322. 

Holmes, M.A., Cockcroft, P.D., Booth, C.E. and Heath, M.F. (2005), Controlled clinical trial of the effect of a homoeopathic nosode on the somatic cell counts in the milk of clinically normal dairy cows . Veterinary Record, 156, 565-567. 

Wilson, D.J., Das, H.H., Gonzalez, R.N. and Sears, P.M. (1997), Association between management practices, dairy herd characteristics, and somatic cell count of bulk tank milk . Journal of the American Veterinary Medical Association, 210, 1499-1502. 

Other proteinases. The presence of low levels of other proteolytic enzymes in milk has been reported (see Fox and McSweeney, 1996). Most of these originate from somatic cells, and their level increases during mastitic infection. The presence of cathepsin D, a lysozomal enzyme, in milk suggests that all the lysozomal proteinases are present in milk although they may not be active. These minor proteinases are considered to be much less significant than plasmin, but more work on the subject is necessary. 

It is a possible index of mastitic infection although the level of LPO in milk increases on mastitic infection, it is not well correlated with somatic cell count. 

Detectable concentrations of various antibacterials in milk attained by different microbiological tests are presented in Table 27.2. Milk constitutes a matrix that, apart from heating to destroy natural inhibitory substances, does not generally necessitate further sample treatment. Some antibiotics, however, exhibit some instability to heat treatment (54-56) and, therefore, if further confirmation is required reference frozen samples should always be available. When raw milk is directly analyzed, critical evaluation is generally required because natural inhibitors such as somatic cells, immunoglobulins, and metabolites may cause zones of inhibition (56, 57). Furthermore, several factors including marked pH-devia-tions, use of paper disks that contain inhibitory substances, and work with forceps that are too hot or have not been cleaned properly can readily lead to falsepositive readings (56, 58). 

Kozanecki, M., Sciubisz, A. and Kasperwicz, A. 1982. Interrelationships between the somatic cell number and lactose level and conductivity in cow s milk and their diagnostic significance in detection of mastitis. Proc. 12th World Cong. Diseases of Cattle 2, 1054-1058. 

Ceriani, R. L., Peterson, J. A., Lee, J. Y., Moncada, R. and Blank, E. W. 1983. Characterization of cell surface antigens of human mammary epithelial cells with monoclonal antibodies prepared against human milk fat globule. Somat. Cell Genet. 9, 415-427. Christie, W. W. and Wooding, F. B. P. 1975. The site of triglyceride biosynthesis in milk. Experientia 31, 1445-1447. 

Proteolysis of casein may be substantial under certain conditions, such as late lactation and mastitic infections. Under these conditions, the number of somatic cells increases. The most noticeable effect of high somatic cell counts is loss of cheese yield. Everson (1984) identified a loss of 0.045 kg of cheese per 45.36 kg of milk for every 106/ml increase of somatic cell count. Somatic cell counts above 4 x 106/ml were also correlated with enhanced lipolysis and with an increased... 

Milk is clarified by high-speed centrifugation to remove extraneous matter held in suspension. Clarification occurs prior to heat treatment of the milk to prevent dissolution of the extraneous matter. Although clarification removes somatic cells, the elevated levels of lipoprotein lipase activators and plasmin that may be associated with increased numbers of white blood cells in the milk are not eliminated. Therefore, increased lipolysis of milk fat by lipoprotein lipase and proteolysis of casein by plasmin may not be deterred. 

Andrews, A. T. 1983B. Breakdown of caseins by proteinases in bovine milks with high somatic cell counts arising from mastitis or infusion with bacterial endotoxin. J. Dairy Res. 50, 57-66. 

Clarification is normally one of the initial steps in processing fluid milk and is important for removing somatic cells, bacteria, and other foreign particles. It is accomplished by passing milk through a rapidly rotating clarifier bowl to sediment suspended particles. 

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