Refrigeration can be divided into high temperature refrigeration, constant temperature refrigeration, low temperature refrigeration, ultra-low temperature refrigeration, quick freezing refrigeration, that is, frozen refrigeration. Generally speaking, poultry, seafood, aquatic products and other categories need to be used in quick-frozen warehouses. Achieve pre-cooling effect in advance. Quick-frozen warehouse refers to a method in which food must reach a specified average temperature of -18°C within a specified time and be quickly frozen. Food will undergo various changes during the freezing process, such as physical changes (volume, thermal conductivity, specific heat, dry consumption changes, etc.), chemical changes (protein changes, color changes, etc.), cell tissue changes, biological and microbial changes, etc. . The characteristic of quick-frozen food is to maintain the original nutritional value, color and aroma of the food to the greatest extent. In other words, during the freezing process, it is necessary to ensure the maximum reversibility of the above-mentioned food changes.
The role of quick freezing warehouse in food preservation:
(1) Avoid the generation of large ice crystals between cells.
(2) Reduce intracellular water leakage and reduce juice loss during thawing.
(3) The contact time between concentrated solutes in cell tissues and food tissues, colloids and various components is significantly shortened, and the harm of concentration is minimized.
(4) Rapidly lowering food to a temperature where microbial growth occurs is beneficial to resisting microbial growth and biochemical reactions.
(5) The shorter the freezing time of food in the freezing equipment, the more conducive to improving equipment utilization and continuous production. Most foods start to freeze when the temperature drops to -1°C. Most of the ice crystals are formed between -1°C and -5°C, which is called the high ice crystal formation stage. Quick freezing can greatly shorten the freezing time at this stage, eliminate this part of heat as soon as possible, and improve the quality of quick-frozen food.