Cheese must be stored properly to prevent deterioration. Most cheeses should be refrigerated; some can be frozen; and processed cheese products can be stored in a cool, preferably dark, cupboard until ready for use, though refrigeration retains desirable qualities more effectively.

Dry Storage. Many process-cheese spreads, as well as the Parmesan cheese sold in cardboard containers, have long shelf storage times. Process-cheese spreads may be safely stored on the shelf in jars at room temperature (70^oF/5^oC) for up to four months, but the quality is better retained if the product is refrigerated. Packaged Parmesan cheese, which has such a high moisture content that it is sold in the refrigerator section.

Refrigeration. Most cheeses are best refrigerated in their original wrappers. Once opened, the cheese should be rewrapped as tightly as possible in its original wrapping or in aluminum foil, plastic wrap, or a sealable bag. This will prevent drying and absorption of odors from other foods. Because their odor may be picked up by other foods, strong-smelling cheeses should be double-wrapped. Properly wrapped cheeses are also protected from the development of molds and their possible mycotoxins. Commercial efforts to reduce molds include coating the cheeses with a wax or resinous material and wrapping them in packaging film. In Europe, the cheese rind is sometimes coated with olive oil to protect it from bacterial contamination, and certain spices applied to the surface of some cheeses for flavor have been reported to have an antifungal effect.

Maximum storage time varies, because no two cheeses are alike. Ripened cheeses can be stored longer than unripened, softer cheeses. Fresh cheeses such as ricotta, cream cheese, and cottage cheese should be used within a week of their sell-by date. Processed cheeses can be stored up to four months because they have been heat treated and contain mold inhibitors. Once opened, processed cheeses should be refrigerated. Unopened Parmesan cheese stores the longest and can be kept up to a year, although the cheese may lose some of its flavor and further dry out. After being opened, Parmesan must be refrigerated.

Cheese that is kept too long can become moldy and/or dry. Most molds that develop on cheese are harmless, but since there are some molds that may produce toxins, all mold should be removed. The FDA Model Codes for Food Service recommends cutting 1 inch beyond the moldy area. Although mold-ripened cheeses such as Roquefort and blue have had special molds purposely added to them, they may develop a different-looking mold on the outside edges, and this should be removed. If soft, unripened cheeses develop molds, they should be discarded. Dried-out cheeses can be salvaged by grating and storing them in the freezer for later use as toppings or in casseroles, sauces, or soups.

Frozen. The water content of a cheese determines whether it can be successfully frozen. Most hard natural cheeses can be frozen for up to two months, and processed cheeses for up to five months, but freezing is not recommended for soft cheeses having a high water content. The most suitable cheeses for freezing include brick, cheedar, Edam, Gouda, Gruyere, Parmesan, provolone, and Swiss. Freezing will change the texture and flavor to some degree, but the cheese should still be acceptable in quality. For best results, cheese should be frozen quickly, and this is best accomplished if it is in half pound pieces not more than 1 inch thick. Larger chinks will freeze more slowly, possibly resulting in crumbly cheese. It is best to freeze cheese in its original wrapper, but the next-best option is to use foil or plastic wrap designated for freezing. It should be wrapped tightly, with excess air being expelled, or else it can dry out.

Just as it is important to freeze quickly, it is also crucial that thawing be gradual. As a result, thawing is best done in the refrigerator over a period of a few days, after which the cheese should be used as soon as possible. Freezing certain cheeses may cause them to develop a dry and crumbly texture, but they may still serve as a shredded or cubed ingredient in a dish even if they would be undesirable in a sandwich or on crackers.

Cooking temperatures for cheeses should be kept low and heating times short. High heat or prolonged cooking toughens cheese proteins and causes the fat to separate out, creating an oily, stringy, and inferior product. When using a microwave, it is best to use lower power settings – between 30 and 70 percent – for melting cheese.

Cheeses used in sauces and other dishes should be added during the last stages of preparation to prevent separation. Adding a pinch of dry mustard to cheese sauces helps to bring out their flavor. One way to soften cream cheese without too much heat is to enclose it in an airtight zip-top plastic bag and briefly submerge it in hot water.

Temperature is also important when serving cheese. Most cheeses (semi-hard and hard) reach their full flavor when taken out of the refrigerator and allowed to reach room temperature before serving. To prevent cheese from drying out, it is best either to cut cheese that has reached room temperature just before serving or to let people cut their own. Cream cheese, cottage cheese, and other unripened cheeses should, however, always be served chilled.

The chemical composition of a cheese determines its functional properties, which dictate how it will be used in food preparation. Some of these functional properties are shredability, meltability, oiling off, blistering, browing, and stretchability.

Shredability. Not all cheeses shred uniformly, which may be important to food service operations interested in cost control. On average, 4 ounces of shredded cheese are equivalent to approximately 1 cup in volume. It may be possible to use less when using aged cheeses because of their stronger flavor. Grating or chopping cheese increases the surface area and thereby increases the ease and speed with which cheese melts.

Meltability. Aged or ripened cheeses such as cheddar and Swiss tend to melt and blend more easily when heated than the less-ripened cheeses. Processed cheese, which contain added water and emulsifiers, can be heated without the fat separating, blend more smoothly, and melt more easily than natural cheeses. The higher the fat and moisture content of a cheese, the greater its meltability. Problems may result when using lower-fat cheeses, because they separate more easily when exposed to high heat, and their higher protein content makes them toughen as they are heated. For these reasons, they are not always good candidates for use in cooking.

Oiling Off. One drawback to using higher-fat cheeses is their greater tendency to “oil-off”, which occurs when some free fat is released and glistens on the surface. The shiny sheen of an oil on pizza may not be appetizing to people, and this is one of the reasons mozzarella cheese, which does not tend to oil off, is used in pizza production.

Blistering. Blistering is another unsightly side effect, with the number and size of the blisters depending on the cheese’s age: large blisters tend to form when using excessively aged cheese, while numerous, small blisters may be a sign that the cheese has not been aged very long.

Browning. The browning of cheeses during heating, a result of the Maillard reaction, is desirable, but only up to a certain point. Too much browning occurs if there is an excess of sugars, amino acids, or lactose in the cheese.

Stretchability. The functionality of a cheese also differs based on how well it stretches. The stretchability of a cheese depends on its concentration of calcium phosphate and is protein network structure. A tough, grainy texture results from the presence of too much calcium, while texture turns excessively soft when undergoing too much protein breakdown during aging.

The two most important principles when preparing foods with cheese are to select the best cheese and to keep temperatures low and heating times short.

A Quality Approved inspection shield on the label means only that the cheese meets minimum quality standards and has been produced in a plant meeting USDA sanitary standards. An imitation cheese is defined as one that looks and tastes like the one it is intended to replace but is nutritionally inferior. Substitute cheeses resemble the traditional product and meet the nutritional equivalence comparisons.

Approximately one-third of the cheese produced in the United States is used for pasteurized processed cheeses. These are called processed cheese, cold-pack cheese, process-cheese food, process-cheese spread, and imitation cheese. Processed cheese was patented in 1916 by James L. Kraft, who founded Kraft Foods. Processed cheeses are all made from blended cheeses, but they differ based on the ingredients and manufacturing methods. These cheeses appeal to many consumers because of their uniform taste and texture, longer shelf life, convenient packaging, and lower cost.

Processed Cheese. Processed cheese is made by combining different varieties of natural cheese. Heating pasteurizes the cheese and stops further ripening, and emulsifying salts, such as sodium citrate or sodium phosphate, are added to produce a stable, homogenous emulsion. During the emulsifying process, powdered milk, whey, cream or butter, and water may be added. The moisture content of the processed cheese must not exceed 40 percent and the fat content is similar to the natural cheese from which it is derived. When the mixture is partially cooled, it is formed into blocks, cut into slices, wedges, or other shapes, and packaged. American cheese made from blended cheddar cheese is a popular form of processed cheese.

Cold-Pack Cheese. Cold-pack or club cheeses were developed in 1918 by Hubert Fasbender, who founded that he could blend cheddar cheese, milk by-products and spices to create a spreadable cheese for use on crackers and sandwiches. Since cold-pack cheeses are blended without being heated, they must be made from pasteurized milk products. In cold-pack cheese food, the original cheese may be combined with milk (whole, reduced fat (2 percent), fat-free (nonfat), or buttermilk), milk solid non-fat (MSNF), cream, or whey. It also may be sold in smoked form.

Process-Cheese Food. Process-cheese food must be at least 51 percent natural cheese by weight, which is less than either processed cheese or cold-pack cheese. The remaining ingredients may include milk, cream, oil or whey. The resulting products, including Cheez Whiz, Velveeta, and Kraft Singles, have a milder flavor and softer texture, and tend to melt more quickly.

Process-Cheese Spread. Process-cheese spread is a softer, more spreadable product than process-cheese food, but, like cheese food, at least 51 percent of its weight must be from natural cheese. Ingredients such as sugar, dextrose, maltose, and corn syrup may also be added. The higher spreadability of process-cheese spread, which makes it ideal for use in sandwiches and on crackers, is obtained by adding more liquid and an emulsifier and reducing the amount of milk fat.

Imitation Cheese. Cheese analogues or imitation cheeses are cheese-like products in which the milk fat natural cheese has been replaced with vegetable oil. These analogues are less expensive than natural cheese and are manufactured using a process similar to that used to make processed cheese. Milk proteins such as calcium caseinate are mixed with a small amount of vegetable fat, water, salt, emulsifiers, and lactic acid before being heated to pasteurization temperatures for several minutes. The liquid is then poured into molds or formed into slices. The texture, flavor, and melting properties of imitation cheeses are similar to processed cheese. Nutritionally, these analogues are lower in cholesterol and sodium, but equivalent in fat, although it is less saturated than that from natural cheese.

Whey separated from its water content is rich in nutrients and low in fat. It contains the water-soluble whey proteins, with most of the lactose, water-soluble vitamins, and minerals of the milk. It is highly perishable when fresh, so it is most often processed quickly into whey cheeses, dry whey, and modified whey products. In the past, the nutrient-rich whey was principally used to feed animals, but now the food industry is using pasteurized whey in a variety of products. Whey is found in baked goods, beverages, sauces, salad dressings, cheese products (dips, spreads, process cheese), canned fruits and vegetables, confections (caramels and other candies), dry mixes, frozen foods (fruits, vegetables, desserts), jams, jellies, meat, pasta, and milk products. A recent development is the use of whey as a component of Simplesse, a fat replacer.

Whey incorporated into foods is available in two types, sweet and acidic whey. Sweet whey results from coagulating milk with rennin, while acid whey originates from acid-coagulated milk. Besides having greater acidic, mineral concentrations are also higher in acid wheys, because the acid releases the calcium from the casein molecule, causing it to be dispersed in the whey portion.

Whey Cheeses. Scandinavian cheeses such as Primost, Mysost, and Gjetost are very hard whey cheeses made by evaporating the water until the whey is extremely concentrated. These cheeses tend to be sweet and lightly brown, a result of their lactose caramelizing in the process of water removal. Another type of whey cheese, ricotta, is produced by coagulating the whey with acid and high heat.

Dry Whey. A large portion of the dry whey produced in the United States is still fed to livestock. The remainder is used as an ingredient in processed foods such as confections, soups, beverages, imitation cheeses, dessert toppings, and nondairy coffee creamers.

Modified Whey Products. Condensed whey contains no more than 10 percent of its original water and is often used as an ingredient in process-cheese food. Another product, sweet-type condensed whey, is used as an ingredient for certain candies. Whey concentrated to contain a minimum of 25 percent protein is labeled “whey protein concentrate”. Removing some of the lactose results in partially delactosed whey. Also available is partially or totally demineralized whey, which has had some or all of its minerals removed.

Many Cheeses are like wine, in that their finished character is determined not only by the original ingredients, but by the maturation process. The aging process whereby cheese is converted from a bland, tough, rubbery, fresh curd into a unique cheese with its own mature flavor, aroma, and texture is called, often interchangeably, curing or ripening. Depending on the variety, cheeses are subjected to different temperatures (36^o to 75^oF/2^o to 24^oC) and humidities (higher for mold-ripened cheeses such as Roquefort and blue). Certain cheeses are treated in such a way as to develop a rind, which is simply the dried surface of the cheese. Ripening times range from four weeks to two years or longer. Cheese becomes stronger in flavor as it ripens; these changes may be observed, for example, in the way cheddar cheese is labeled as mild, medium, or sharp.

Cheese flavor developed during curing and ripening originates from a combination of over 300 different volatile and nonvolatile compound. It is believed that some of these compounds originate from the milk, the activity of milk enzymes, and the starter bacteria. The skillful adjustment of curing techniques, along with the maintenance of the proper environment of temperature and humidity, creates the desired flavors, textures, and aromas of the multitude of cheeses available in our markets. During ripening, a number of elements may be manipulated to affect the final product. Added salt will draw out some of the remaining whey and inhibit bacterial growth, thereby slowing down the ripening process. Bacteria and molds contribute to the development of flavors, aromas, and texture. The mold Penicillium roqueforti added to homogenized while milk converts free fatty acids to smaller compounds, which impart the characteristic tangy flavor to blue cheese. The holes (eyes) in Swiss cheese are produced by gas-forming microorganisms that are active during the early part of ripening when the curd is pliable. Other processes that influence flavor during ripening include the hydrolysis of proteins to peptides (smaller protein molecules) and amino acids, the conversion of lactose to lactic acid, and the breakdown of fatty acids into shorter, volatile fatty acids.

Cheeses may exhibit different textures due to processing techniques during production, two of which are inoculation and kneading. The blue-veined cheese have been inoculated with mold spores, whose growth within the cheese creates the blue veins. Mozzarella and provolone are ropy in texture due to kneading, which is the pulling and stretching of the curd after it has been knitted.

The curd may be treated to remove more whey by cutting, heating, and salting. Optional further treatment includes knitting and/or pressing. Although a few chemical tests can be made to assess the progress of the curd through each of these treatments, it is often the experienced judgment of a cheese maker that determines when it is time for the next step.

• Cutting. Slicing the curd increases its surface area. Sometimes the curd is placed on strainers to remove even more whey.
• Heating. Encourages the evaporation of whey and allows lactic acid to build up to create a firmer, more elastic texture. Heat also destroys certain undesirable microorganisms. After heating, the curds are washed with cold water to produce softer, higher-moisture cheeses.
• Salting. Further dehydrates the curd, controls the growth of bacteria, and contributes to the flavor, texture, and appearance of cheese.
• Knitting. Some cheese are “knitted”; that is, the curd is united or melted into a solid mass through the use of heat.
• Pressing. Pressing is another way to create a solid mass out of the curd, the the last step before ripening. Curds are physically pressed into compact masses by placing them in boxes or other containers under pressure.

Cheese-making starts with the coagulation of the casein protein in milk. The two main methods by which coagulation can occur are by the action of enzymes or acid. The type of method used determines many of the characteristics of the resulting cheese.

Enzyme Coagulation. The enzyme most commonly used to coagulate milk in cheese-making is rennin, obtained from milk-fed calves, specifically their forth stomach. Rennin, also called chymosin, is sold commercially as rennet. Other sources of available rennin include cows, pigs, plant sources, and genetically engineered bacterial. Alternatively, enzymes may be derived from bacterial starters (Streptococci, Lactobacilli), from certain molds, or from any of a number of other microorganisms. The different enzymes, bacteria, molds, and/or yeasts added during coagulation influence the flavor, texture, and color developed by the cheese during ripening.

The milk is usually heated in large vats at temperatures from 72 to 95F (22 to 35C) to provide an optimal environment for enzymes and bacterial activity, which contributes to the formation of curd. Calcium chloride may be added to speed up coagulation and strengthen the curd’s consistency. Coagulation with enzymes occurs in less than an hour, and creates a tough, rubbery curd. As the curd forms, the whey separates, but most of the milk’s calcium remains in the curd.

Acid Coagulation. There are two methods by which acid may be used to coagulate milk proteins and thus form cheese. The first method is to simply add acid directly to the milk. The second, more complex, method is to inoculate the milk with cultures of bacteria that convert lactose (milk sugar) to lactic acid, which makes the milk medium more acidic. Bacterial cultures have been used for centuries to produce fermented foods, and are carefully selected for their characteristic influences on a cheese’s flavor and texture. It takes from four to sixteen hours to coagulate milk with acid-forming bacteria. About one-fourth to one-half of the calcium in milk is lost in the whey during this process. Curd produced by acid has a soft and spongy texture. This texture is influenced by pH, becoming more solid and compact as the acidity increases. Acid-coagulated cheese is usually not aged because its high acidity inhibits the bacterial and mold growth that characterizes the aging process.