Dairy bacterial count

J. D. Findlay, C. Higginbottom, J. A. B. Smith, and C. H. Lea, The effect of the pre-heating temperature on the bacterial count and storage life of whole milk powder spray-dried by the Krause process, J. Dairy Res., 1946, 14, 378-399. 

The microbial treatment under microwaves uradiation is a function of power, firequency range, time and temperature. The technique using fixed frequency microwaves has been used in the pasteurization of milk, yoghurt and dairy products and has had an effect on reducing the bacterial count and deactivating enzymes at a lower energy input level and destruction as compared with conventional means of pasteurization techniques in use (US Food and Dmg Administration 2000). 

Dairy products. Fresh milk is subject to off-flavour development due to microbial activity. When supplied by the cow, milk has a bacterial count of less than 500 colony forming units/ml (CFU/ml) and when this reaches 10 CFU/ml the flavour becomes unacceptable (Paine and Paine, 1983). The traditional packaging used for pasteurised milk is the glass bottle. This was replaced by the waxed carton as early as 1940 in the USA, although over 90% of milk was supplied in glass in the UK and... 

A study of 28 dairy farms in The Netherlands found that the introduction of an automatic milking system led to a reduction in milk quality compared to conventional farms, owing to an increase in the total bacterial plate count and of free fatty acids (Klungel et al., 2000). 

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. 

The dye 4, 6-Diamidino-2-PhenyIindole (DAPI) in 0.001%W/V aqueous solution can be used directly on smears, ciyosections and embedded specimens to locate and count culture bacteria, without regard to their viability, in cheese and other cultured products. The dye reacts with nucleic acids by intercalation. Excitation at 360nm is best for this dye. It is worth noting two other facts about its use. DAPI cross reacts with dairy proteins, but the color of the protein-dye complex is different from that of the nucleic acid-dye complex (the latter is a steely blue/white) and so the two reactions may be discriminated. The dye also may take up to 15 minutes to enter bacterial cells, particularly spores, before fluorescence is observed. An alternative nucleic acid dye, Ethidium Bromide, has less contrast between the fluorescence induced in cells and the fluorescence of cross-reacting dairy proteins. It should be tried in other products such as meats if DAPI is not successful. 

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