What Temperature Should a Cold Storage Be Set to Ensure Items Are Fully Frozen?

To ensure items are fully frozen, the temperature setting of a cold storage is not simply about going as low as possible; it requires following the scientific principles of food freezing and precisely matching different freezing needs. Generally, setting the cold storage temperature at -18°C or below meets the standard for long-term frozen storage, while achieving rapid freezing requires an even lower temperature range.

During the cooling process, food passes through a zone known as the "large ice crystal formation zone," typically between -1°C and -5°C. If food remains in this temperature range for too long, large ice crystals form inside the food cells, puncturing the cell walls, leading to significant juice loss and deteriorated texture after thawing. Therefore, to rapidly freeze food while maintaining quality, it is essential to pass through this zone quickly.

For different freezing requirements, the temperature standards for cold storage are mainly divided into the following tiers:

First, the standard freezer storage, typically set between -18°C and -25°C. At this temperature, the moisture inside the food freezes into a solid state, and the reproduction of microorganisms and enzyme activity are greatly inhibited, enabling long-term preservation of items such as meat, seafood, and frozen foods. For most everyday frozen products, -18°C is the golden threshold to ensure they are fully frozen and remain unspoiled.

Second, the blast freezer, which typically requires temperatures between -30°C and -40°C. The core function of a blast freezer is to rapidly reduce the core temperature of food to below -18°C within a short time. Due to the rapid cooling, small and uniform ice crystals form both inside and outside the food cells, without damaging the cellular structure. This method of freezing can lock in the freshness, moisture, and nutrients of the ingredients to the greatest extent, and the texture after thawing is almost identical to that of fresh ingredients.

Furthermore, for high-end seafood such as tuna or special biological products, an ultra-low temperature environment of -45°C to -60°C or even lower is required. Such low temperatures not only freeze the ingredients instantly but also effectively prevent fat oxidation and protein denaturation, ensuring the ingredients retain a bright color and firm texture.

In actual operation, to ensure items are properly frozen, in addition to setting the appropriate temperature, attention must also be paid to the method of loading into the storage. Freshly harvested or freshly slaughtered items carry a significant amount of field heat or body heat. If placed directly into the freezer, it can cause drastic temperature fluctuations in the storage, affecting the quality of other already frozen items. The correct approach is to first place them in a pre-cooling room to lower the temperature before transferring them to the freezing area. Additionally, items should be stacked with ventilation gaps to ensure cold air can penetrate evenly, avoiding localized incomplete freezing.

In summary, to ensure items are fully frozen, standard freezing requires temperatures of -18°C or below, while rapid freezing requires a blast freezing environment of -30°C to -40°C. Scientific temperature settings combined with standardized operating procedures can ensure freezing effectiveness while preserving the original quality of the items to the greatest extent.

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