Blue Cheese And Listeria: What's The Real Danger?

Blue cheese is a type of cheese that is ripened with Penicillium mould, resulting in a network of blue and green veins throughout the cheese. It includes varieties such as Danish Blue, Roquefort, Stilton, and Gorgonzola. Blue cheese has been associated with listeria outbreaks, with the presence of Listeria monocytogenes detected in some blue cheese products. Listeria is a foodborne bacterial illness that can pose serious health risks, particularly for vulnerable individuals such as pregnant women, the elderly, and those with weakened immune systems. While the frequency of listeriosis from consuming blue cheese is considered very low, the severity of infection in vulnerable individuals can be high.

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Blue cheese is defined as cheese internally ripened with Penicillium mould

Blue cheese is a type of cheese characterised by blue-green spots or veins throughout its body. It is made by adding cultures of edible moulds, specifically, the fungus Penicillium roqueforti. Other species of the Penicillium genus used in blue cheese production include Penicillium glaucum and Penicillium camemberti. The moulds are added as a starter culture during cheese production, and their growth leads to the production of volatile and non-volatile flavour components, changes in cheese texture, and the characteristic blue-green veins.

The process of making blue cheese consists of six standard steps, with additional ingredients and processes to create the particular properties of blue-veined cheese. Blue cheese is believed to have been discovered by accident when cheeses were stored in caves with naturally controlled temperature and moisture levels, which created a favourable environment for the growth of harmless moulds. Today, blue cheeses are typically aged in temperature-controlled environments, with the temperature and humidity closely monitored to ensure the cheese does not spoil and develops optimal flavour and texture. The ripening temperature is generally around 8 to 10 degrees Celsius, with a relative humidity of 85-95%.

During the ripening process, the cheese loaves are punctured to create small openings to allow air to penetrate and support the growth of the aerobic Penicillium roqueforti cultures, thus encouraging the formation of blue veins. The total ketone content is also constantly monitored as the distinctive flavour and aroma of blue cheese arise from methyl ketones, which are a metabolic product of Penicillium roqueforti.

Blue cheese is associated with a higher risk of listeria outbreaks, particularly when made under unsanitary conditions. Listeria is a foodborne bacterial illness that can be very serious, especially for older adults, those with weakened immune systems, and pregnant women and their newborns. Soft cheeses, such as blue cheese, are more likely to be contaminated with listeria, and the risk for listeriosis per serving is much higher for cheese made from unpasteurized milk. Therefore, it is recommended that those who are pregnant or immunocompromised avoid consuming soft cheeses, including blue cheese, unless it is clear from the packaging that the product was made with pasteurized milk.

Blue cheese is made from pasteurised milk and is generally considered low risk

Blue cheese is a type of soft cheese, and soft cheeses have been associated with listeriosis outbreaks worldwide. However, it's important to understand the process of pasteurization and its role in mitigating the risk of listeria contamination in cheese products.

Pasteurization is a process of heating milk to a specific temperature for a set period, effectively killing the Listeria monocytogenes bacterium. Therefore, cheeses made with pasteurized milk, like most blue cheeses sold in the UK, are generally considered lower-risk for listeria contamination. This is because the pasteurization process eliminates the bacterium from the milk used in cheese production.

However, it is essential to recognize that contamination can still occur after pasteurization due to inadequate hygiene practices or other factors. For instance, data from Scottish local authorities and the Food Standards Agency revealed that a small percentage of blue cheese samples were contaminated with L. monocytogenes, including some pasteurized varieties. Similarly, a US retail survey from 2000 to 2001 detected L. monocytogenes in 0.5% of cheeses made from pasteurized milk.

While blue cheese made from pasteurized milk is generally considered lower risk for listeria, vulnerable individuals, including pregnant women, the elderly, infants, and those with weakened immune systems, should still exercise caution. This is because the severity of a Listeria monocytogenes infection in vulnerable people can be high, leading to severe illness or even life-threatening complications. Therefore, it is always advisable to follow food safety guidelines, store cheese products according to instructions, and maintain good personal hygiene to minimize the risk of listeria infection.

Listeria bacteria can be found in soil, water and animal faeces

Listeria is a foodborne bacterial illness that can be very serious for some people. The bacteria, Listeria monocytogenes (L. monocytogenes), is widespread in the environment, especially in soil, water, and animal faeces. It can survive in soil for many months and can tolerate a wide range of conditions, including acidic and salty environments, as well as high and low temperatures. This makes it difficult to control and it can result in the intermittent contamination of food.

L. monocytogenes can be found in the faeces of animals, particularly cattle, who can carry the bacteria without appearing sick. It can then be transmitted to humans through contaminated food or water. Listeriosis, the disease caused by L. monocytogenes, can have severe consequences for those with weakened immune systems, such as older adults, pregnant women, and their unborn babies.

In pregnant women, listeriosis may cause only mild symptoms, but it can lead to devastating consequences for the unborn baby, including pregnancy loss or a life-threatening infection within a few days of birth. For this reason, pregnant women are advised to avoid soft cheeses, such as feta, brie, Camembert, blue cheese, and Mexican-style cheeses, unless it is clear that the product was made with pasteurized milk.

L. monocytogenes can grow at refrigeration temperatures, so simply refrigerating food may not be enough to prevent contamination. However, pasteurization is effective at killing the bacteria, and proper hygiene practices can help to prevent contamination after pasteurization. To minimize the risk of listeriosis, it is important to follow food safety guidelines, such as regularly cleaning and sanitizing surfaces and utensils, and washing hands with soap and warm water before and after handling food.

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Listeria infection is likely to be mild for mothers but can be devastating for unborn babies

Listeria is a foodborne bacterial illness that can be very serious for some people. Listeria bacteria can be found in soil, water, animal feces, and certain processed foods. It is known to contaminate raw vegetables and processed foods such as soft cheeses, hot dogs, and deli meats.

Blue cheese is one of the soft cheeses that have been associated with listeria outbreaks. In a US retail survey of several soft cheeses from 2000 to 2001, 1.3% of blue-veined cheeses made from unlabeled or unpasteurized milk were found to contain Listeria monocytogenes.

Pregnant women are about 10 times more likely to get listeriosis than other healthy adults due to changes in their immune systems. While listeria infection may cause only mild, flu-like symptoms in pregnant women, it can have devastating consequences for their unborn babies. Listeria infection during pregnancy can lead to miscarriage, stillbirth, premature delivery, or infant death. Even if the mother exhibits no symptoms, the baby can still be born with listeriosis and become seriously ill.

To reduce the risk of listeria infection during pregnancy, it is recommended to avoid soft cheeses such as blue cheese unless the packaging indicates that the product was made with pasteurized milk. Other high-risk foods to avoid include hot dogs, deli meats, meat spreads, smoked seafood, and refrigerated ready-to-eat foods. It is also important to practice good hygiene and food safety practices, such as thoroughly washing fruits and vegetables and avoiding food past its expiration date.

The risk of listeria in blue cheese is considered very low, but the severity is high

Blue cheese is a type of soft cheese that has been implicated in listeriosis outbreaks worldwide. Listeriosis is a foodborne bacterial illness that can be very serious for some people. The bacteria can be found in soil, water, and animal feces, and people can become infected by eating contaminated raw vegetables or processed foods such as soft cheeses, hot dogs, and deli meats.

The risk of listeria in blue cheese is considered very low, especially in cheeses made with pasteurized milk. Pasteurization kills the Listeria monocytogenes bacterium, which is the most common cause of listeriosis infections. However, contamination can still occur after pasteurization due to inadequate hygiene practices.

According to a UK Food Standards Agency (FSA) and Food Standards Scotland (FSS) risk assessment, the frequency of listeriosis in vulnerable people from consuming blue cheese is very low. Vulnerable people include pregnant women, people over 65, infants, and those with weakened immune systems. The assessment found that vulnerable people do not frequently consume blue cheese and when they do, it is usually in low amounts.

While the risk of listeria in blue cheese is low, the severity of infection is high. Listeria monocytogenes can cause severe illness and even death, especially in vulnerable individuals. Therefore, it is important to take precautions when consuming blue cheese, especially for those who are vulnerable to infection.

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