The freezing speed of liquid nitrogen is crucial to the quality of food, the faster the freezing speed, the less damage to the cells. For most foods, there is a dangerous temperature zone, which is -1°C to -5°C, also called "ice crystal formation zone". If it is at this temperature for a long time, 80% of the water in the food cells will be lost. The longer this temperature is left, the more severely the cell membrane is damaged, and the more nutrients of the food will be lost after thawing. Regardless of whether it is freezing or thawing, it is best to let the food pass through the "ice crystal formation zone" within 30 minutes.

Freezing can reduce the reproduction speed of bacteria in food and make most bacteria "dormant", but it is not absolute. Some bacteria can still survive in ultra-low temperature environment, so the food after refrigeration will also deteriorate, which is why even Frozen food should also be marked with a shelf life. The shelf life is calculated after evaluating various indicators. These indicators include the speed of microbial reproduction in the food at low temperature, and after leaving the factory, the taste and flavor of the food are deteriorating with time. Slow oxidation, vitamins are also gradually broken down.