Your refrigerator is designed to keep dairy products and other highly perishable foods at a safe temperature of 40 degrees Fahrenheit or below. But in real life, temperatures are not consistent throughout your entire fridge. Furthermore, dairy products vary in their perishability. Matching the most perishable dairy products with the coldest locations in your refrigerator provides a simple and pragmatic way to adapt to those two realities.
Fluid milk is among the most perishable of foods, and on a warm day can start to sour in a matter of just hours. Fridges are often designed to accommodate milk in their doors, but the door -- which is exposed to warm air every time you open it -- is a poor place for milk. Instead, milk and cream should be kept near the back of a low shelf in your refrigerator, where the temperature is colder and more stable. Fresh cheeses such as ricotta or queso blanco are also highly susceptible to spoilage and to foodborne bacteria, and similarly benefit from storage in the coldest part of your fridge.
Some of the best-loved dairy products are cultured with beneficial bacteria, including yogurt, buttermilk, sour cream and cheeses. The rich flavors and thick textures of these products are caused by beneficial bacteria, which consume the milk's natural sugars and convert them to mild malic and lactic acids. As a bonus, this naturally occurring acidity acts as a preservative, discouraging the growth of many molds and rival bacteria. Because they're less perishable, these products can be safely stored on the upper shelves of your refrigerator, where temperatures are slightly warmer.
Aged cheeses are more robust than fresh cheeses and must be handled differently. The cheeses need to "breathe" to retain their flavor and texture, so they shouldn't be wrapped directly in foil or plastic. Instead, wrap them in paper -- specialized cheese paper if you have it, parchment or wax paper if you don't -- and then loosely in foil or a plastic bag. This way moisture isn't trapped against the cheese, where it can promote the growth of mold. Cheeses can be stored in a crisper drawer, which retains more humidity than the rest of the fridge, or in a plastic tub on an upper shelf. Blue cheeses and cheeses with a mold-based rind, such as Brie, should be kept apart from other cheeses to prevent their molds from spreading. Hard cheeses, such as Parmesan, are especially durable and can be stored in the fridge door or any other convenient location.
Ice cream and similar products such as ice milk and frozen yogurt have their own storage requirements. They'll retain their quality longest at the very low temperatures found in a deep freeze, but this leaves the dessert rock-hard and inconveniently difficult to scoop. In the front of your refrigerator's freezer compartment the ice cream remains soft and scoopable, but the opening and closing of the freezer door -- with its attendant change in temperature -- can promote the growth of ice crystals and spoil the ice cream's texture. Keeping your ice cream in a back corner of the fridge freezer is a good compromise, maintaining both quality and ease of scooping.
Aside from firm cheeses, which are fuller in flavor if they're allowed to come to room temperature before serving, dairy products should be kept cold at all times. If you're transporting dairy products to a get-together or taking them on a road trip, try to replicate your normal storage conditions as closely as possible. Ice cream should ideally be packed in its own cooler, surrounded by frozen gel packs. Milk and cream can be nestled into loose ice or sequestered in one end of a larger picnic cooler where they're in direct contact with several gel packs. Less-perishable items such as yogurt and firm cheeses require less cooling, often only one or two gel packs for short trips of just a few hours.