By Nicole Martin, MS
They’re furry and they’re fizzy. They’re green, yellow, white and black. They’re fungi and they might be spoiling your dairy foods. In fact, some reports estimate that as much as 5-10% of all food production worldwide is lost to spoilage by fungal microorganisms. But what are fungi and what are these microorganisms doing in dairy products?
Fungi are a diverse group of microorganisms that include yeasts, molds and mushrooms. As with other foodborne microorganisms (i.e., bacteria), fungi can be beneficial (e.g., Penicillium camemberti is responsible for the bloomy rind found on camembert and other similar cheeses), cause spoilage (e.g., Candida sp. and other yeasts are common yogurt spoilage microorganisms), and even be pathogenic (e.g., Aspergillus flavus can produce aflatoxin).
Fungi are found in diverse environments from soil, water and plant material to food processing facilities. They are known for their ability to grow over a wide range of water activity, pH and temperatures, which gives them the unique ability to thrive in conditions that many bacteria cannot. In fact, it is this ability of some yeasts and molds to grow in low pH and low temperature conditions that presents a particular problem for some dairy processors, especially those that manufacture yogurt and other cultured products. This type of fungal spoilage, which can result in consumer dissatisfaction has even led to several recent large scale dairy industry recalls for premature spoilage.
The ubiquitous nature of fungal spoilage microorganisms, their ability to grow under adverse conditions (e.g., low pH) and the relative ease with which they are transferred within an environment (e.g., via air) all make contamination with fungal spoilage microorganisms a challenge for the dairy industry. Research focusing on understanding the natural fungal populations in raw materials as well as the environments where yeasts and molds can survive in processing facilities will assist the dairy industry in reducing the risk of product contamination. Additionally, the development of source tracking tools that have been used for both pathogenic and spoilage bacteria in the food industry is another area of research that is critical to identifying and eliminating fungal contamination in dairy products.
The Milk Quality Improvement Program laboratory offers services to assist dairy processors in identification of fungal microorganisms in environmental and product samples. Further information can be obtained by contacting Nicole Martin, nhw6@cornell.edu, 607-255-2894.
