Fermented Solid Dairy Productscheese

Cheese is made by the coagulation or precipitation of milk protein by acid produced by starter cultures (S. [L.] lactis and S. fL.] cremoris) with the aid of rennin (from the stomach of calves) added to the milk. Milk is usually pasteurized at 62.8°C for 30 min or 72.0°C for 15 s. Raw milk has been used to make cheese but is not advisable due to the potential of survival of foodborne pathogens such as Listeria monocytogenes. Regulations indicate the cheese made with raw milk cannot be sold until a 60-day aging period. The assumption is that in 60 days pathogens, if present in the cheese, will be killed by the starter cultures and the acidity involved in the product. A food-grade dye, annatto, is often added to give the cheese the familiar yellow color. Some cheese makers are now not using the dye so that the cheese will not have additives in the product. When milk proteins coagulate, the resultant liquid portion is called whey. From 10 lb of milk, only 1 lb of cheese is made and 9 lb are discarded as whey. Whey utilization is an important area of research because whey has very high biological oxygen demand (BOD) (30,000-60,000 ppm) and can be an important environmental contaminant if the BOD is not reduced. Also, whey contains about 50 to 70% of the nutrients of milk, and this rich food source should be effectively utilized. After the curd is formed, it can be poured into perforated molds lined with cheesecloth, and the extra whey is drained. For harder cheese, the curd is cooked, stirred, cut, and pressed. The more whey expressed from the protein mass, the harder the resultant cheese will be. Salt is often added to the curd to give flavor as well as to prevent undesirable microorganisms from growing. Cheese is then ripened for several months or even years before consumption.

Classification of Cheese

There are literally hundreds of cheese varieties being made in the world. Most of the names are from the town or city in which the cheese originated. From a texture point of view, cheese can be classified into the following.

Soft, Unripened or Ripened Cheeses. Cottage cheese is an example of soft, unripened cheese. It can be made by acid produced by the starter cultures (Lactococcus lactics and L. cremoris) along with rennin or by direct set using food-grade acid such as mesolactide and d-glucono-J-lactone. For the direct set method, the cottage cheese will coagulate very fast—within seconds at 4°C. For starter cultures, one can use a "short set" method by inoculating the milk with 5% starter cultures, and the process will be completed in 5 h. For the "long set" method, a 3% percent inoculation can be used, and it will take 10 to 14 h to complete the process. After setting the curd, it be cut using 1/4" wire for small-curd cottage cheese and 3/4" wire for large-curd cottage cheese.

Soft, Ripened Cheeses. Limburger cheese is an example of soft, ripened cheese. The soft cheese is placed on wooden shelves, and a surface bacterium (Brevibacterium linens) grows on the surface of the cheese and produces a brownish red surface growth. Protein is broken down into ammonia and gives the strong flavor to this cheese. Camembert cheese is another soft cheese, but it is ripened by a surface mold, Penicillium camemberti, with a mixture of bacteria. This famous French cheese is called the queen of cheese.

Semisoft, Ripened Cheeses. Several mold-ripened cheeses are classified under this category. They are all ripened by Penicillium roqueforti, a mold that grows throughout the cheese mass. They are also called blue-veined cheese. Roquefort cheese is called the king of cheese. Other cheeses in this group are Stilton, Gorgonzola, and bleu.

Hard Cheeses. These cheeses are well ripened and hard. Among the most important cheeses are cheddar, a bacterial-ripened cheese, and Swiss cheeses, which are cheeses with eyes. The characteristics eyes of Swiss cheeses are caused by C02 produced by Propionibacterium shermanii during anaerobic fermentation in the ripening stage.

Cheese Varieties and Descriptions

Principal cheese varieties and descriptions are as follows (4).

American. This term is used to identify the group that includes cheddar, Colby, and so on, popularized in the United States.

Bleu. The French name, bleu, is used for cheese similar to Roquefort but either not made in Roquefort, France, or not made from ewe's milk.

Blue. Roquefort-type cheese made in the United States and Canada is referred to as blue. Brick cheese, of American origin, is made from whole milk, with a mild but pungent and sweet flavor.

Cheddar. This is the most important cheese and accounts for 75% of cheese made in the United States. The name came from the town Cheddar in the UK where it was first made. In addition, cheddaring is the name of a step in the manufacturing process of piling and repiling of curd. This will provide better adhesiveness of the protein and also allow starter cultures to produce more acid to control coliforms. Most cheddar cheeses are ripened for 60 days and some for a year or more (sharp and very sharp cheddar).

Colby. Similar to cheddar, Colby has a softer body and more open texture.

Cottage. A soft unripened cheese, cottage cheese is made from skim milk. Flavoring materials such as peppers, olives, pimientos, or garlic may be added. When more than 4% of fat is added, it is called creamed cottage cheese.

Cream. Cream cheese is a soft, rich, unripened cheese made of cream or a mixture of cream and milk.

Edam. Made from whole milk, Edam has a mild flavor and firm body. It is usually shaped like a flattened ball and covered with red coloring or red paraffin.

Gouda. Gouda is similar to Edam, except that it contains more fat and is usually packaged like Edam.

Limburger. A soft, surface-ripened cheese, Limburger has a characteristic strong flavor and aroma.

Parmesan. A very hard cheese that will keep almost indefinitely, Parmesan is used as grated cheese on salads, soups, and with pasta.

Process Cheese. Process cheese is made by grinding and mixing together by heating and stirring one or more naturally fermented cheese of the same or different varieties, together with an emulsifying agent into a homogenous mass at very high temperature (130°C) for a few seconds. After the mixture has been properly prepared, the cheese can be made into various thickness, shapes, and forms. Also, a variety of ingredients such as bacon, spices, port wine, and so on can be incorporated into the cheese. At least one-third of all cheese marketed in the United States, except soft, unripened cheese, is process cheese.

Process Cheese Food. Process cheese food is made in the same way as process cheese, except that certain dairy products (cream, milk, skim milk, cheese whey, or whey albumin) may be added. At least 51% of the weight of the finished product must be cheese.

Process Cheese Spread. This is made in the same way as process cheese food, except that it contains more moisture and less fat and must be spreadable at a temperature of 21.1°C (70°F). Fruits, vegetables, or meats may be added.

Roquefort. A cheese made only in the Roquefort area of France from ewe's milk, Roquefort is characterized by sharp, peppery flavor and blue-green veins throughout the cheese. It is ripened principally by blue mold in the interior.

Swiss. A hard cheese with an elastic body, nutlike flavor, Swiss cheese is best known by the holes or eyes that develop as the cheese ripens.

An excellence reference set—Cheese and Fermented Milk Foods Vol 1: Origins and Principles and Vol 2: Procedures and Analysis—that covers all aspects of fermented diary foods was published by Kosikowski and Mistry (5).

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