How are High Somatic Cell Counts Cutting into Your Cheese Production?
The effects of elevated Somatic Cell Count (SCC) on milk production are well documented; yield is decreased and quality is lowered through physical defects or altered fat/protein composition.
However, the consequences don’t stop there. For producers shipping milk to be further processed into other dairy products such as cheese, there is a whole other level of factors that high counts can influence. The principle factors are the yield and properties of casein contained in this milk, enzyme activity and chemical products of an immune response.
These factors influence the technological usability of the milk in processing as well as the quality and yield of the final products. In addition to avoiding penalties and obtaining premiums, keeping your SCC low has a significant impact on further manufacturing of your milk.
Casein is the component that determines the stability of milk during processing, including the methods of pasteurization and sterilization. A high SCC, with or without the presence of clinical mastitis, affects the production of casein in a number of ways.
According to the National Mastitis Council, although an SCC of 200,000 is considered safe and healthy, even an SCC as low as 100,000 for an individual cow and approximately 500,000 for bulk tank milk can adversely affect production (Western Canadian Dairy Herd Improvement Services, 1997). Casein molecules accumulate in micelles; spherical lipid molecules that form in liquids such as milk (Janjic & Hoffman, 1974).
Since lipid components tend to separate from water and aggregate in a layer, in normal milk this is prevented by negative charges on the micelles causing them to repel each other (Laht, 2008). High SCC degrades the structure of casein molecules, thereby decreases the size of individual micelles along with increasing the aggregation of micelles due to the decreased electrostatic molecular repulsion.
The average size and distribution of micelles determine the textural properties of products as well as the water holding capacity of those products that undergo a fermentation process. Decreased textural properties result in lower quality products such as cheese and yogurt, decreasing sale value and product demand.
High SCC also increases production of plasmin and plasminogen, which have proteolytic activity. Proteolysis is the breakdown of larger proteins into smaller polypeptides or amino acids, usually naturally catalyzed by enzymes in the body to increase the speed of the process (Encyclopaedia Britannica Inc., 2016). The abnormally high proteolytic activity caused by elevated SCC affects the milk’s ability to withstand thermal processing without casein and fat component quality and yield degrading.
This degradation decreases the coagulation properties necessary for processing and results in bitterness when hydrophobic peptides are released from casein. The activity of enzymes also leads to poor curdling and continues during cold storage, further altering coagulation properties and resulting in age gelation of Ultra- High Temperature processed dairy products.
The decreased electrostatic repulsion of casein micelles destabilizes milk being processed into gelled products including cheese, yogurt and ice cream. All of these effects of elevated SCC serve to decrease the total yield of manufactured products obtained from the milk, as well as decrease their quality and shelf life.
Immune Response and Antibiotics
Elevated SCC is closely linked to the occurrence of mastitis, and even trace amounts of antimicrobials used in its treatment or prevention (such as germicidal teat dips) can inhibit starter microorganisms added during manufacturing. Since elevated SCC levels reflect increased immune response, the rate of oxygen radicals produced as part of leukocyte activity increases.
Oxygen radicals are formed in the place of water when insufficient electrons are transferred from fats and carbohydrates to oxygen atoms (University of Washington, 2016). Small amounts of oxygen radicals are a normal product of metabolism but high levels are harmful due to their extremely reactive nature and can damage macromolecules such as DNA, proteins and lipids. When oxygen radicals react with lipids found in milk the effect is a bitter taste and/or “off” smell.
The immune response reflected by high SCC and the associated mastitis treatment/prevention methods alter milk properties to result in increased manufacturing costs and decreased quality of product.
The benefits of maintaining low SCC levels goes beyond the price obtained for the bulk tank. SCC has a dramatic effect on casein properties, which determines stability during processing and therefore affects coagulation properties, yield and quality of the dairy products manufactured from high SCC milk. Enzyme activity and cellular products of immune response yield lower quality products that may have altered textural properties, taste, smell and shelf life.
In addition to lowering the price obtained for poor milk used in manufacturing, lower quality products diminish consumer opinion of the producer, decreasing demand for that producer’s products. Maintaining low SCC benefits the whole supply chain, from individual cow to herd to consumers.
Are you having difficulties finding a solution to reduce your milk SCC levels? We offer instant, on-farm milk testing to help you take control of your business and implement effective milk quality control. Contact us, or visit our Dairy Health Check page for more information.
Encyclopaedia Britannica Inc. (2016, May 30). Proteolysis. Retrieved from Encyclopaedia Brittanica Online: http://www.britannica.com/science/proteolysis
Janjic, T., & Hoffman, H. (1974). Mechanism of micelle formation. Chemischer Informationsdienst.
Laht, T.-M. (2008). Rennet coagulation of milk. Retrieved from Tallinn University of Technology: www.umb.no/statisk/nordost/laht_renneting_jurmala.pdf
University of Washington. (2016, May 30). Oxygen Radicals. Retrieved from http://courses.washington.edu/conj/bloodcells/oxygenradicals.htm
Western Canadian Dairy Herd Improvement Services. (1997). DHI Somatic Cell Counts. Retrieved from Agromedia: www.agromedia.ca/ADM_Articles/content/dhi_scc
About the Author
Anna Schwanke is an undergraduate student at the University of Guelph, Ontario. She is responsible for researching and writing about a wide variety of topics related to dairy cow welfare and management for Dairy Quality Inc. The 10 years she spent living in Australia, as well as her love of travelling, give her a firsthand viewpoint of issues facing the international dairy community. She plans to graduate from the University’s College of Physical & Engineering Science in 2019 and pursue a career in the Life Sciences or Agriculture industry.
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