Food Protection Connection: Are You a Cheese Safety Whiz?

(reprinted from Dietary Manager, April 2009)

If you are like most dietary managers, you probably use cheese in your menus routinely. If so, it’s not surprising, as about one-third of all the milk produced in the US goes into cheese production. Cheese, as a high-protein food rich in calcium and other nutrients, does carry its own food safety risks. Are you a cheese safety “whiz?” Let’s find out! Try guessing whether each statement that follows is fact or fiction.

Fact or Fiction?

Really, the only potential hazard in cheese is Listeria monocytogenes.

Fiction! Other documented hazards include Staphylococcus aureus, E. coli, tuberculosis, and Salmonella enteritidis, not to mention mold toxins.

Fact or Fiction?

Unpasteurized milk is the greatest hazard.

Fact! A surprising number of cheeses are made from unpasteurized milk—missing an opportunity to destroy pathogens at the outset of processing. For example, just a few years ago, the FDA warned US consumers of the dangers of Queso fresco style cheese, a soft white unripened cheese, imported from Mexico. The FDA cautioned, “There is some risk of infection from a number of pathogenic bacteria for anyone who eats raw milk soft cheese from any source.” The FDA Food Code (3-202.14) advises, “Cheese shall be obtained pasteurized unless alternative procedures to pasteurization are specified…”

Fact or Fiction?

Listeriosis is of grave danger to pregnant women.

Fact! Pregnant women are particularly susceptible to Listeriosis, and the illness can lead to miscarriage or stillbirth. About one-third of Listeriosis cases in the US involve pregnant women.

Fact or Fiction?

The key source of Listeria bacteria in cheese is the cheese processing plant.

Fiction! The FDA says that this bacterium is widely present in soil and water, and can show up in farm animals’ systems. A dairy cow can harbor Listeria without appearing ill. Unpasteurized (raw) milk or foods made from unpasteurized milk may likewise be contaminated.

Fact or Fiction?

Pathogens such as Listeria stop growing as long as cheese is refrigerated.

Fiction! Listeria bacteria are infamous for their ability to continue growing even at refrigeration temperatures. This means the combination of time and temperature management are critical for controlling the hazard. (The same is true for deli meats and some other ready-to-eat products, which may not undergo further cooking before being served.)

Fact or Fiction?

If cheese is made from pasteurized milk, all hazards are eliminated.

Fiction! Scientists note that even with pasteurized milk, cheese production requires attention to food safety. The brine used in processing, for example, can support growth of E. coli bacteria.

Fact or Fiction?

Mold and bacteria play roles in cheese production.

Fact! A cheese that is “ripened” gains flavor from the byproducts of microbial action. Cheddar, Swiss, and Parmesan cheese, for example, are ripened by bacteria in a controlled production process. Bleu, Roquefort, and Brie cheeses are ripened by molds. These processes do not use pathogens. Remember that many safe microorganisms contribute to production of products like cheese, yogurt, buttermilk… even beer and wine. Byproducts of the microbes’ action contribute to characteristic flavors of these products.

Fact or Fiction?

Hard cheeses have a longer “shelf life.”

Fact! That’s a shelf in the refrigerator, by the way! Also, remember to keep cheese tightly wrapped in airtight packaging to control both safety and quality, and date-mark opened packages.

Fact or Fiction?

Shredded cheddar cheese keeps just as long as block cheddar.

Fiction! Any time cheese is shredded, its safe storage time decreases. Shredded cheese has much more air-contact surface area, which means it can become dehydrated, as well as more readily come in contact with airborne molds.

Fact or Fiction?

Soft cheeses are, generally speaking, more hazardous than hard cheeses.

Fact! All other factors being equal, a soft cheese (e.g., cream cheese, ricotta, cottage cheese)—or a semi-soft cheese (e.g., Havarti, Monterey Jack, mozzarella, Muenster, provolone)—contains a higher water content than a hard cheese. Hard cheeses typically contain less than 39 percent water, whereas soft cheeses may be 50 percent. You probably remember from a study of “POTTWA” that high water activity is one of the factors that supports bacterial growth. It’s easier for pathogens to flourish in a soft cheese, compared with a hard cheese. This doesn’t mean that soft cheeses produced from pasteurized milk are inherently dangerous. However, it does mean they have a shorter safe storage time.

Fact or Fiction?

Because cheeses are “cured,” temperature management is not critical.

Fiction! Cheeses, like any potentially hazardous food, need to be kept cold (40˚F or below). More storage tips: The Clemson University Extension Service also advises, “If cheese is removed from its original packaging, wrap it tightly with plastic film wrap or foil to prevent air pockets. Once cheese is exposed to air, molding and dehydration might occur. To protect cheese from mold it is best to double-wrap cheese and place it in a sealed container after each use.”

Fact or Fiction?

If cheddar cheese grows mold, you can cut off the moldy part and use the rest.

Fact! For a hard cheese, experts advise it is safe to cut off the moldy portions plus an additional half-inch all the way around. Not all molds are dangerous, but some molds produce toxins that can cause foodborne illness. (Even though this procedure is considered safe for hard cheeses, don’t try it on all moldy foods. Bread, soft vegetables, and many other food products need to be discarded once mold appears. In high-moisture foods, mold sets up a network of microbes throughout the food product. Even sections that don’t look moldy can in fact harbor mold.)

Fact or Fiction?

Wrapping cheese tightly can help prevent mold.

Fact! Remember that mold is airborne. Wrapping limits contact with air.

Fact or Fiction?

It’s safe to freeze cheese.

Fact! However, you can expect changes in texture. Cheese may become crumbly, and is likely to work best in a casserole, salad, or soup. According to the National Dairy Council, some cheeses withstand freezing better than others. The Dairy Council also suggests freezing cheese in units of one-half pound or less, wrapping tightly, freezing quickly, thawing in the refrigerator, and using as soon as possible thereafter.

Sue Grossbauer, RD, author of several books, and a regular contributor to DIETARY MANAGER magazine.