Feta cheese, a soft, brined cheese, is a popular ingredient, but its consumption often raises questions during pregnancy. Many soft cheeses are restricted due to food safety concerns. However, applying heat significantly modifies the safety profile, often allowing them to be safely enjoyed. This preparation change directly addresses the underlying risk factors.
Why Soft Cheeses Pose a Risk
Soft cheeses, including feta, pose a risk during pregnancy because they can harbor the bacterium Listeria monocytogenes. This organism is unique because it can grow and multiply even at refrigerator temperatures, making it a persistent food safety concern. The high moisture and lower acidity in soft cheeses create an environment where this bacteria thrives more easily than in harder varieties.
Infection with this pathogen leads to listeriosis, which is particularly dangerous for pregnant individuals, who are about ten times more likely to contract the illness. Hormonal changes during pregnancy naturally lower the immune system’s effectiveness, making it harder to fight off the infection. While symptoms in the mother may be mild, the consequences for the developing fetus can be severe.
Listeriosis can cross the placenta, infecting the amniotic fluid and the baby. This can result in complications such as miscarriage, stillbirth, premature birth, or severe infection in the newborn, including meningitis. Medical guidance advises caution regarding any food item that could potentially contain Listeria monocytogenes.
The Safety Difference Between Pasteurized and Unpasteurized Feta
The initial defense against bacterial contamination is pasteurization, a process that involves heating milk to a specific temperature before cheese-making begins. This thermal treatment is designed to destroy harmful pathogens, including Listeria monocytogenes, present in raw milk. Consequently, feta made from pasteurized milk is generally considered safe to eat uncooked during pregnancy.
Commercially produced feta in countries like the United States and Canada is frequently made with pasteurized milk, which significantly mitigates the risk. However, feta made from unpasteurized or raw milk carries a much higher risk of contamination and must be strictly avoided unless cooked. This raw milk feta is more common in imported, artisanal, or farmer’s market varieties, so always check the product label for the word “pasteurized.”
Even when feta is made from pasteurized milk, some food safety authorities still recommend caution, as contamination can occur after pasteurization during the cheese-making, storage, or handling process. The extended shelf-life and refrigeration of soft cheese also provide the bacteria a window to multiply if it was introduced post-pasteurization. Cooking the cheese is often recommended as the safest and most definitive method to eliminate any remaining risk.
How High Temperatures Eliminate Risk
The application of high heat is a reliable method for destroying Listeria monocytogenes bacteria. The thermal death point for this pathogen is well-established, and heating the contaminated food to a specific internal temperature will effectively eliminate it. The necessary internal temperature to ensure the destruction of Listeria is 165°F (74°C).
To achieve this level of safety, the feta cheese must be cooked thoroughly until it is steaming hot throughout its entirety. Simply warming the cheese or having it melt slightly on a piece of warm food is not sufficient to reach the required internal temperature. When adding feta to a dish like a casserole, pizza, or baked pasta, the cheese should be bubbling and fully incorporated into the hot food.
Practical applications include using feta in baked dishes, such as a baked feta pasta, or as a topping on a pizza that is cooked completely through. It is also important to observe strict guidance on preventing cross-contamination. If cooked feta is placed on a plate or cutting board that previously held the raw cheese, the risk of transferring the bacteria returns, negating the benefit of cooking. Always use clean utensils and surfaces when handling the cooked product.