Mozzarella

The first step in the creation of mozzarella cheese is pasteurization of the milk. Mozzarella is a fresh cheese, consumed without aging and so milk used must be pasteurized to ensure the safety of the cheese. Once the cheesemilk is prepared, starter culture is added to generate lactic acid from lactose and this acid production, along with activity of added rennet, serves to produce the casein coagulum. The casein coagulum is then cut to release some whey from the curd and the whey isdrainedoff.The curds are then formed into blocks and allowed to ripen slightly until the pH has been lowered to approximately 5.2.The blocks are then milled and the curds are then heated in hot water and mixed and stretched to orient the protein and fat components of the cheese and generate the characteristic mozzarella texture. The heat involved in this treatment also denatures the rennet enzyme and prevents proteolysis in the curd. The curd is then molded into the proper form and transferred into a brine solution for several hours. The brining step allows salt to migrate into the cheese for both flavour and preservative effects. Brining also stops the activity of the starter cultures. Mozzarella is a cheese that is high in moisture and fairly high in lactose since some whey is retained, the starter organisms are inhibited and also there is no aging time (where moisture would evaporate and lactose would be converted to lactic acid). The lack of aging also limits the amount of proteolysis and lipolysis that occurs. These factors, combined with the denaturation of the rennet enzyme, result in a cheese with a very mild flavour. Given the relatively bland flavour of mozzarella, it is possible to replace the use of starter culture by the direct addition of food grade acid. Once the curd is formed by this method, the remaining cheesemaking steps are as detailed above. Another processing option is to produce mozzarella by a stirred curd process. In this process, after draining the whey, the curds are constantly stirred while the pH is lowered to 5.2, instead of being formed into blocks. As a result, there is no need for milling before the heating and stretching step.

There are a number of variations of mozzarella cheese. Some mozzarellas have more of their whey removed (casein coagulum is cut and warmed rather than just cut) resulting in a final cheese with a lower moisture content. These mozzarellas are easier to slice and are intended for use on pizzas, and are termed low moisture mozzarellas or pizza cheese. Regular mozzarellas and the low moisture pizza version can also be produced from either whole milk or skim milk resulting in four variations.

Mozzarella cheese is used as an ingredient to add sensory appeal, mild flavour, and nutritional value to foods. Mozzarella cheese is high in protein and each serving provides a source of calcium, phosphorous, zinc and Vitamins B12 and A.

Cheese is of high nutritional value due to its high concentration of proteins. Casein contains various levels of all the essential amino acids although it is relatively low in sulfur containing amino acids. As a result, the protein quality of cheese is slightly less than that of milk, which retains the sulfur rich whey proteins. However, the protein quality of mozzarella is slightly better than cheeses where more of the whey is removed.

In terms of microbiological standards, all cheeses made from pasteurized milk must contain fewer than 100 Escherichia coliper gram and fewer than 100 Staphylococcus aureus per gram.

Mozzarella cheese can be used in any number of products and goes well with various meats and vegetables. Mozzarella cheese and tomatoes make a particularly excellent pairing. Of course, the best known use of mozzarella cheese is in Italian dishes such as lasagna and melted on top of pizza.

• Pizza: mozzarella cheese provides mild flavour, visual appeal and characteristic textures when melted on the surface of a pizza. Mozzarella melts smoothly and browns nicely when baked. The melted cheese is very elastic and is very stretchy and stringy, contributing to the sensory appeal and "fun factor".
• Baked goods: mozzarella cheese can be melted on the surface of baked goods to provide visual and textural appeal as for pizza.
• Soups and sauces: mozzarella cheese can be melted into a soup or sauce to provide body and texture as well as some mild flavour.
• Italian dishes: mozzarella cheese baked into dishes will provide flavour, as well as textural benefits including the stretch and stringiness of the melted cheese.
• Appetizers: the flavour and stretchiness of the cheese adds appeal to appetizers such as breaded and fried mozzarella.

• The casein proteins in mozzarella are in such a form that the cheese is very elastic and has a high degree of stretchability. The pH of the curd is the critical factor in determining stretchability as pH influences the state of the casein molecules.
• Mozzarella cheese is primarily added to a product for its melting behaviour. The characteristic protein/fat network allows the cheese to melt smoothly without as much separation of the oil phase as occurs when melting many other cheeses.
• When mozzarella cheese is heated it undergoes browning, including the Maillard reaction of proteins with residual lactose. This browning can add visual appeal to cooked products.
• Mozzarella has a mild flavour that can compliment a product.
• Mozzarella cheese has a light colour but can attractively contrast dark sauces.
• Melted mozzarella can be used to add viscosity to soups and sauces.
• Melted mozzarella cheese on the surface of products such as pizzas and baked goods improves the sensory appeal of these products.
• Mozzarella has a soft-to-firm texture. However, when melted, the texture of mozzarella cheese becomes smooth and creamy.
• Mozzarella cheese is an excellent addition to cooked products but care should be taken to ensure that the cheese is not overheated. Over cooking of cheese can cause fat separation and protein denaturation, which unfavourably alters the properties of the cheese, particularly related to texture and appearance.

For more information on cheese, please visit the University of Guelph's Dairy Science and Technology Web site.