An overview of selected “subzero” temperature storage regimes of foods: regulations and perspectives about the expected impact of the "three degrees of change" initiative on the shelf life of frozen foods

Frozen storage temperature plays a crucial role in preserving the initial quality of frozen foods. The most used storage temperature of frozen food is -18°C and is based on 0°F, which corresponds to -17.8°C. This temperature does not correlate with a specific ratio of frozen water in foods (“level of frozenness"-LOF) and has been arbitrarily chosen. The fact is that at -18°C, most foods never reach a 100 % LOF (usually in the range of 95 % LOF). The 100 % LOF refers to a state in which the maximum ice crystallization zone has been covered (usually around -30°C). New low-temperature storage modes, such as chilling, superchilling, and supercooling, gained attention in academia and in the food industry, pushing the boundaries of existing regulations. The recent "Three Degrees if Change" initiative launched by the University of Birmingham (UK) aims at exploring the interest and impact of changing the frozen food storage temperature from -18°C to -15°C. This paper proposes a review of the current regulations in connection with selected subzero temperature storages. Based on the principle of the Q₁₀ models, a Q3 model is proposed showing that frozen foods stored at -15°C may lose around 30 % of their quality life from the sensorial point of view. Raising the temperature to -15°C should not pose a major microbial risk; however, this point must be under scrutiny. In particular, the permitted temperature oscillations during transport and at the retail outlet may require some adjustment.