Guest Columns

Industry Issues

Dairy product quality and biofilms

John Lucey

John Lucey is director of the Wisconsin Center for Dairy Research at the University of Wisconsin-Madison. He is a guest columnist for this week’s Cheese Market News®.

As the dairy industry knows, product quality can be jeopardized by the development of a biofilm. Whether the biofilm issue starts on the farm or develops in the dairy plant equipment, identifying and eliminating a biofilm can be a time-consuming and expensive undertaking for any operation.

To provide the industry with the latest insights into milk quality issues, including biofilms, a session titled “Milk Quality, Biofilms and Dairy Products” was held at the April 2013 Wisconsin Cheese Industry Conference in La Crosse, Wis. Speakers included Dr. Bernadette O’Brien, from the Moorepark Research Centre, Ireland; Dr. Mark Johnson from the Wisconsin Center for Dairy Research; Tony Erickson, principal chemist at Ecolab; and Karl Kieffer, Tetra Pak Inc. They discussed a range of issues including international perspectives on milk quality, biofilm formation, sanitation and spore control. During the discussion, three key points were continually reinforced by members of the panel: the importance of understanding biofilms, preventing biofilms and monitoring for a biofilm.

Improving milk quality is an important topic not just in the United States but globally, as was reflected in many of the examples given in this session. Dr. O’Brien described milk quality improvement programs in New Zealand and Ireland geared toward reducing total bacteria and somatic cell counts on the farm. These strategies include penalties for exceeding maximum levels, online resources to deal with seasonal mastitis issues, setting of goals for an individual farm, detailed protocols for drying-off and mastitis treatment, etc.

Dr. Johnson emphasized that we need to better understand the importance of biofilms, their prevention, and how to know if you have a biofilm issue (in order to take corrective action). Simply put, a biofilm is a result of the adherence of microorganisms to a surface. More specifically, a biofilm occurs when bacteria begin to build up inside of equipment. As the microorganism population increases they secrete a sticky material, known as exopolysaccharides, which is responsible for the gooey film that makes biofilms so hard to remove. As the biofilm development enters its later phases, it becomes more likely that microorganisms from the original biofilm may slough off and contaminate another area of the equipment/product. Biofilm development can reduce flow of liquids through some equipment, causing resistance to standard chemical and sanitation approaches, and they contaminate new milk streams with high numbers of their host bacteria. Given the concerns over biofilms, it is important to monitor all areas of production for signs of biofilm formation. Dr. Johnson pointed out several “red flags” that can indicate a biofilm formation somewhere in the system. These signs include a high number of Lactobacillus bacteria in pasteurized milk, faster rates of acidification in cheese vats later in the day and a glistening surface or film on equipment.

Erickson discussed various strategies to prevent and remove biofilms and spore-formers. Some biofilm issues start on the farm as research shows that buildup on milking equipment and non-hygienic milking practices can contribute to the formation of biofilms; however, these causes can be hard to trace. Buildup in the gaskets of pasteurizers, difficult to reach areas like dead-ends or straight angles for pipes, low flow areas, or cooler regions within equipment (which may not achieve the correct “hot” cleaning temperature during CIP) also are possible causes. Keep in mind that biofilms can take a long time to build up, and standard CIP chemistry is less effective on established biofilms so they also can take a long to time to remove. To control spores in milk powders the target should not only be the raw milk supply, but also biofilms in evaporators and related equipment. Erickson suggested considering options like peracid sanitizing, intermediate peracid flushes, intermediate quick-clean and “hot” sanitizer use as possible interventions but each method comes with benefits and drawbacks so finding the correct method can take a bit of experimentation and research. Ecolab is partnering with companies to research best-practice intervention outcomes.

To avoid biofilms in equipment, Tetra Pak’s Karl Kieffer recommended short run times for heat exchangers (with proper cleaning and sanitation between runs) or having a second heat exchanger (in parallel) to allow processing to continue while the other heat exchanger unit is undergoing CIP. Other suggestions include minimizing the size of heat exchangers to have less residence time and keeping milk temperatures as low as possible to reduce the possibility of bacterial growth. Bactofugation (can be installed in series to increase the efficiency of spore removal) and microfiltration are two separation technologies available for spore removal from raw milk.

Biofilms are the natural state of microorganisms in the environment, so continued research into this area will be necessary as we work to limit the negative effects of biofilms on the dairy industry. Cleaning and sanitation programs are always essential elements of high-quality dairy products and close attention to the biofilm issue both on the farm and in milk processing facilities will help industry to prevent this costly issue and will lead to more consistent, high-quality dairy products.


The views expressed by CMN’s guest columnists are their own opinions and do not necessarily reflect those of Cheese Market News®.

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