There are hundreds of varieties of cheese, each prepared by a different process, but typical steps include bringing the temperature of nrilk to about 30°C and then adding several substances, including a cheese starter and sometimes rennet. Part of the mixture solidifies into the curds, from which the liquid whey is drained. A curing period in refrigerated rooms follows for most cheeses at temperature of the order of 10°C. Beverages Refrigeration is essential in the production of such beverages as concentrated fruit juice, beer, and wine. The taste of many drinks can be improved by serving them cold.

Juice concentrates are popular because of their high quality and reasonable cost. It is less expensive to concentrate the juice close to the orchards and ship it in its frozen state than to ship the raw fruit. To preserve the taste of juice, its water must be boiled off at a low temperature, requiring the entire process to be carried out at pressures much below atmospheric.

In the brewing industry refrigeration controls the fermentation reaction and preserves some of the intermediate and final products. A key process in the production of alcohol is fermentation, an exothermic reaction. For producing a lager-type beer, fermentation should proceed at a temperature between 8 and 12°C, which is maintained by refrigeration. From this point on in the process the beer is stored in bulk and ulti mately bottled or kegged in refrigerated spaces.

The major reason for refrigerating bakery products is to provide a better match between production and demand and thus prevent waste. Many breads and pastries are frozen following baking to provide a longer shelf life before being sold to the consumer. A practice that provides freshly baked products (and the enticing aroma as well) in individual supermarkets but achieves some of the advantages of high production is to prepare the dough in a central location, freeze it, and then transport it to the supermarket, where it is baked as needed.

Some biological and food products are preserved by freeze drying, in which the product is frozen and then the water is removed by sublimation (direct transition from ice to water vapor). The process takes place in a vacuum while heat is carefully applied to the product to provide the heat of sublimation. Some manufacturers of instant coffee use the freeze-drying process.

Chemical and process industries The chemical and process industries include th manufacturers of chemicals, petroleum refiners, petrochemical plants, paper and pul industries, etc. These industries require good engineering for their refrigeration since almost every installation is different and the cost of each installation is so high. Some important functions served by refrigeration in the chemical and process industries are separation of gases, condensation of gases, solidification of one substance in a mixture to separate it from others, maintenance of alow temperature of stored liquid so that the pressure will not be excessive, and removal of heat of reaction.

A mixture of hydrocarbon gases can be separated into its constituents by cooling the mixture so that the substance with the high-temperature boiling point condenses and can be physically removed from the remaining gas. Sometimes in petrochemical plants hydrocarbons, such as propane, are used as the refrigerant. Propane is relatively low in cost compared with other refrigerants, and the plant is completely equipped to handle flammable substances. In other applications separate refrigeration units, such as the large packaged unit, provide refrigeration for the process.