Somatic Cells Reduce Quality of Milk as well as Dairy Products

Dairy Pipeline: March 2000

Gerald M. (Jerry) Jones
Professor and Extension Dairy Scientist, Milk Quality and Milking Management
Virginia Tech
(540) 231-4764
gmjones@vt.edu

For some time, it has been known that higher somatic cell counts reduce cheese yield, affect cheese curd firmness, increase fat and casein loss in whey, and compromise dairy product sensory quality. Research conducted at Cornell University has recently found that quality of pasteurized milk decreased when milk with high somatic cell counts was used.

Streptococcal mastitis was created in 8 Holstein cows and milk was collected and pasteurized. Prior to infection, these cows averaged 87 lb. milk per day with an average somatic cell count below 45,000. After becoming infected, somatic cell count was approximately 750,000 (the legal limit in the USA) and milk production dropped to 61 lb. According to the research team, milk from these infected cows lacked freshness, was unclean, was less sweet and smelled different from normal milk. The milk was rancid and bitter. Shelf life was decreased and high somatic cell count milk showed more breakdown of milk fat and protein. Compare this to high quality milk which should have a pleasing, slightly sweet taste, with no unpleasant after taste. Milk should be free from pathogenic (disease-causing) bacteria, have somatic cell counts less than 200,000, and bacteria counts below 5,000. Milk should be free from drug and pesticide residues, other adulterants, and foreign materials (sediment such as dirt, etc.), and have no off flavors.

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