Rapid cooling of fruit
Apples need to be cooled as quickly as possible in order to provide the longest duration of storage and to provide the highest quality.
To ensure that stores are loaded and the operating temperatures are achieved within 5 days of the start of loading the following points should be observed:
- The desired cooling rates will not be achieved unless the store is well insulated and there is sufficient refrigeration capacity to bring to bear during the pull-down period.
- Walls of new stores should be made of 100-125 mm of quadcore panels with U values of 0.15-0.18 W/m2 K.
- Ceiling panels should have at least 125 mm quadcore composite panels.
- The core insulation should be HCFC, CFC and HFC free and meet LP.C.B standards of certification.
- Construction of floor panels should include 50-75 mm polyisocyanurate (PIR) core.
- All insulated panels should meet LPS 1181 Reaction to fire test.
- When an LPS 1181 certified product is used, checks must be made to ensure the construction that was tested and certified is fit for purpose.
- If a standard, such as LPS 1181, is being used as part of the ‘holistic’ fire risk assessment, it is important to note that different grades, such as EXT-A and EXT-B, are always qualified with the phrase ‘as tested’ and that grades only apply to the system or construction that was fire tested. Check that the details and materials in the full test certificate and Red Book Live are the ones actually specified and installed. If not, there is the real likelihood that there will be no certified fire performance.
- The store air must be circulated quickly and distributed evenly through the whole of the stored product.
- The fans should be capable of producing forty changes of the store volume every hour.
- Allow at least a 50 mm gap between each tier of bins.
- Bins of fruit should be loaded into a store that has been cooled thoroughly for at least 2 weeks before loading.
- This ensures that the refrigeration plant is extracting primarily the field-heat of the apples and does not have to cope with undue heat ingress through the structure and to some extent the cold structure provides a small ‘ice-bank’ effect.
- It is important that during loading the refrigeration plant is switched off.
- The plant should be switched on when the door is not likely to be opened for some time.