Dairy Foods: Milk, Cheese, Yogurt, Butter, Ice Cream

 

Dairy foods come from milk produced by animals, includ­ing cows, goats and sheep. Like meat, poultry, eggs and seafood, dairy foods have the potential to cause foodborne illness. These foods come from animals or fish that may carry pathogenic, or "sick-making," organ­isms, including bacteria, viruses and parasites.

PASTEURIZATION

What makes dairy foods different from meat, poultry, seafood and eggs is that most milk is pasteurized before it is sold as liquid milk, or before being made into cheese or ice cream.   

NOTE: For information on Raw or Unpasteurized Milk, Cheese, or other Dairy Products, see the fact sheet - Raw Dairy Foods

Regulations

In 1924, the United States Public Health Service (USPHS) developed the Standard Milk Ordinance, which was not a regulation, but guidance, and encouraged states to adopt it. This ordinance has been through several iterations and is now known as the Grade “A” Pasteurized Milk Ordinance; the most recent version being published in 2003.  The PMO is a set of requirements for milk production, milk hauling, pasteurization, product safety, equipment sanitation and labeling.  Most states, including Connecticut, have adopted this ordinance as their method of regulation of dairy products.

How milk is pasteurized

During pasteurization, raw milk is heated while being agitated or shaken so that every particle of milk, includ­ing the foam, reaches a temperature of 145° F. It is then held at that tempera­ture for 30 minutes. A second method of pasteurization is to heat milk to 161° F and hold for 30 seconds. This heating process destroys the microor­ganisms that cause illness. Pasteurized milk is the base for ice cream, yogurt and certain beverages, as well as for cheese.

Pasteurized milk and dairy products made from pasteurized milk are considered to be free of pathogenic microorganisms.  But, if not handled safely, pathogenic microorganisms may con­taminate the dairy products, making them a source of foodborne illness. It is important that you purchase dairy products from a refrigerator case in a reputable market. Get the food home as soon as possible and into the refrigerator. Do not leave dairy products out at room temperature; return dairy products to the refrigerator as soon as you have served them.

BUYING AND STORING DAIRY FOODS

Milk and processed dairy foods are closely regulated by the state and federal govern­ments. However, consumers need to be aware of how to handle dairy products to keep them safe and wholesome.

Sell by date

Many dairy products are marked with a "sell-by" date. Retail stores must pull dairy products off the shelf after this date.  However, this date is NOT the date on which you must dispose of the milk, yogurt, sour cream or cottage cheese.  If dairy products were handled safely and kept at 40° F or below during transportation and storage, you will still have as many as five to seven days after that date to consume the dairy products.  Spoilage bacteria and yeasts are likely to grow in the products after five to seven days. You will usually notice an off-odor or off-flavor, or the growth of mold or yeasts when dairy products are spoiled.

Make sure that all dairy products are refrigerated and cold to the touch when you buy them. In Connecti­cut, all dairy products must be under refrigeration in the market. Do not buy containers that are dam­aged or leaking, or are miss­ing a plastic seal on the lid, if one should be there.

When you get home, refrigerate your dairy products immediately in the original container. The temper­ature of your refrigerator should be 38° to 40° F.

Storage times for best quality (time after the "sell-by" date, or once the container is opened)

Milk, Cream………………………………………………1 week

Butter …………………………………………………....2 weeks

Buttermilk, Sour Cream, Dips ……………………......2 weeks

Yogurt   …………………………………………………..2 weeks

Cottage Cheese, Ricotta ……………………………....5 days

Cream Cheese            ……………………………........2 weeks

Hard Cheese………………………………………………3-4 weeks, once opened

Processed Cheese………………………………………..3-4 weeks, once opened

Freezing milk, cream, or cheese

Most fresh dairy products do not freeze well. Milk and cream, for exam­ple, change in texture, body and appearance, and there may be a sepa­ration of the fat emulsion. Thawed cream may not whip well. However, you can freeze butter made from pas­teurized cream for three to four months. Cheese can be frozen but there may be changes in texture. Hard cheese will become crumbly. Cheese can be frozen in blocks or grated. Cheese, like other high fat foods, may absorb flavors from other foods stored in the freezer. To prevent this, tightly package all foods in moisture- and vapor-proof materials, such as freezer bags, freezer wraps or hard plastic containers.

PREPARING AND HANDLING DAIRY FOODS

Fresh, pasteurized milk and cream

Keep milk and cream in the refrigera­tor at all times. Return milk to the refrigerator as soon as you have served it. Room temperatures will speed up the activity of spoilage organisms.

Do not return unused milk to its original container. Store it separately, or throw it out.

Soft cheeses

Cottage cheese, farmer's cheese, cream cheese, ricotta, brie and camembert are all examples of "soft" cheeses. These cheeses have a shorter shelf life than hard cheeses. Be sure to keep these cheeses refrigerated at all times. If left at room temperature for more than two hours, bacteria and other microorganisms could contaminate the cheese, multiply and make the cheese unsafe to eat. In addition, if mold is found on these cheeses, the cheese should be thrown out. If molds are on the rind of the cheese - not on the cheese itself -you may simply discard the rind and eat the cheese.

Hard cheeses

Cheddar, Swiss and Gouda are "hard" cheeses. These cheeses have a longer shelf life than soft cheeses because of their lower moisture content. They will maintain quality longest if stored in the refrigerator, but they can tolerate longer periods of time at room temperature. Spoilage generally appears as mold on the cheese. Because these cheeses are hard, mold filaments are not as likely to penetrate far into the cheese. If a small amount of mold is on the cheese, simply cut off the mold and about one inch of the cheese it covers. When large amounts of mold cover the cheese, it is best to throw it out.

Yogurt, buttermilk, and sour cream

These products are made from milk that has been treated with beneficial bacteria that create an acid that "sours" the milk, causing it to thicken. Keep these products refrigerated at all times. Like soft cheeses, if left at room temperature for more than two hours, bacteria and other microorganisms could contaminate the yogurt, butter­milk or sour cream, multiply and make the cheese unsafe to eat. When mold appears on these products, throw them out.

Butter

While few outbreaks of foodborne illness have been documented, butter is a potentially risky food - it is derived from an animal product and can support the growth of bacteria and other microorganisms. Though it is made from pasteurized cream, there is a chance that butter could become con­taminated by bacteria if left at room temperature. Cross-contamination is a concern because consumers may use a knife that has cut meat, cheese, lettuce or other potentially contami­nated foods before using it on the butter. Keep butter in the refrigerator at all times. Refrigerate right after meals - do not let it sit at room tem­perature for long periods of time.

Ice cream and frozen dairy desserts

These foods are stored in the freezer, where bacteria and other microorgan­isms do not multiply. However, there is the potential of cross-contamina­tion from dirty utensils. Use a clean scoop when serving ice cream. Do not let scoops sit in water for more than two hours without washing and sani­tizing for another use. Ice cream and other frozen dairy desserts, are best when stored in a freezer at 0°F to 10°F. For best quality, use within one month.

Want to read more?

Milk, cheese and dairy products, FoodSafety.Gov

National Dairy Council Food Safety Fact Sheet