3 degrees of change

The ‘Three Degrees of Change - Frozen food in a resilient and sustainable food system’ report was published last year to coincide with COP28 (3 degrees report). Currently frozen food is generally maintained at -18°C or lower in the food cold chain. The report raises the question of whether frozen food temperatures could be increased to -15°C which would save energy and the associated carbon emissions. Across the whole frozen food chain (from production to the consumer) a refrigeration energy saving of 5-7% was predicted.
-15°C provides a reasonable margin of safety as microbes that are found on food do not grow below -12°C. Raising the storage temperature may, however, have an impact of food quality as chemical and enzymatic changes will still occur and will be greater at -15°C than at -18°C. The report predicted the impact of moving from -18°C to -15°C on the vitamin C levels in spinach and found that vitamin C levels reduced below threshold levels after approximately 110 days at -15°C whereas at -18°C they remained at acceptable levels for approximately 175 days. Foods storage duration is therefore critical, and this is something that needs further investigation.
Some companies have already started to assess the impact of raising frozen food temperatures by 3°C. William Morrisons started testing the concept in 10 stores in August 2024 (William Morrisons). Although raising the set point temperature of frozen food cabinets in supermarkets is a simple measure, it should ideally be accompanied by optimisation of the operation of compressor packs and ultimately purchasing cabinets that are designed for the higher temperatures. A temperature classification that enables cabinets to be tested to a maximum temperature of -15°C already exists within BS EN ISO 23953 (Refrigerated display cabinets, Part 2: Classification, requirements and test conditions). The L3 classification requires all the test packs loaded into a cabinet to be colder or equal to -15°C at some stage during the test and no warmer than -12°C at any stage.
Currently very few cabinets are tested to the L3 classification, in fact only 0.2% (1.8% of frozen cabinets listed) of the cabinets listed on the European Product Registry for Energy Labelling (EPREL) are classified as L3. Interestingly the average Energy Efficiency Index (EEI) of L3 cabinets which is used for energy labelling is 70.5 (equivalent to an ‘F’ label). L1 cabinets (test packs loaded into a cabinet are colder or equal to -18°C at some stage during the test and no warmer than -15°C at any stage) which should use more energy have an average EEI of 62 (an ‘E’ energy label). Thermodynamically this does not make sense as L3 cabinets could consume approximately 6% lower energy in EN23953 than an L1 cabinet (based on Carnot efficiency where L1 cabinets evaporate at -28°C and condensation temperature is 35°C as prescribed in BS EN ISO 23953).
It therefore appears that L3 cabinets have not undergone as much optimisation as L1 cabinets which currently dominate the market (90% of frozen cabinets on EPREL are L1). If L3 cabinets were to become the norm, then many L1 cabinets could be operated and tested to L3. This would then enable the energy and carbon emission savings that could be achieved by raising storage temperature by 3° to be defined.
One interesting associated point is that for both L1 and L3 cabinets listed on the EPREL there is a large range in the EEI’s presented. For both categories, EEIs of between 7 and 100 are listed. Some of these differences are related to different cabinet configurations and how the EEIs are generated in the energy labelling calculation. Even so, the large range in performance reported indicates that there are significant opportunities to improve efficiency of frozen cabinets and that this could provide considerable additional savings to those that could be achieved by raising storage temperatures by 3°.
If you would like to know more about testing to EN ISO 23953-2:2023, optimising cabinet performance or energy labelling, then please contact Judith Evans (j.a.evans@rdandt.co.uk) at RD&T. We would also like to send you all our best wishes for Christmas and hope that 2025 is a successful and rewarding year.