Freezing is a method of food preservation that slows the physical changes and chemical and microbiological activity that cause deterioration in foods. Reducing temperature slows molecular and microbial activity in food, thus extending useful storage life. Although every product has an individual ideal storage temperature, most frozen food products are stored at 0 to –30°F (–18 to –35°C).. Chapter 21 lists frozen storage temperatures for specific products. This chapter covers general freezing methods and systems. Additional information on freezing specific products is covered in Chapters 23, 30 to 33, and 38 to 42. Related information can be obtained in Chapters 19 and 20, which cover thermal properties of foods as well as their cooling and freezing times. Information on refrigeration system practices is given in Chapters 1 to 4. Freezing Methods Blast Freezers Contact Freezers Cryogenic Freezers Cryomechanical Freezers Other Freezer Selection Criteria Refrigeration Systems