Good temperature control is fundamentally important in minimising moisture loss, avoiding condensation, preventing disease development and extending saleable life. Monitoring vegetable temperatures is therefore one of the easiest ways to assess where damage may be occurring and also prevent it from happening in the future.
Temperature measurements during shipping and transport used to involve large, unwieldy and relatively insensitive chart recorders that had to be retrieved and visually scanned for problems. Temperatures can now be recorded using tiny, inexpensive data recorders little bigger than a watch battery. They can record air temperatures (and humidity, if required) on the outside of a pallet, inside a carton, or inside the flesh of the product itself.
Data loggers are available that are GPS enabled, allowing the consignment to be tracked and monitored while it is en route. Some are designed to be single- use, avoiding the need for them to be returned for downloading; the finder simply plugs them into a computer or scans using a mobile phone, and the data can be automatically streamed back to source. Temperature monitoring systems are available that are entirely automated, avoiding any need for retrieval and downloading.
Measuring temperatures has therefore never been easier, and is likely to continue to get better as technology improves.
Temperature monitoring within supply chains can provide invaluable information about how products are being managed. If pallets are left on a dock in the sun, or inside a truck with the cooling system turned off, then this can account for significant loss of quality further along the supply chain. Conversely, if chilling sensitive products get too cold, this can also affect subsequent quality, even if the effects are not noticed straight away.
An example of temperature monitoring within a supply chain is shown below. In this case, bitter melon from a farm in the Northern Territory was being shipped to Sydney Markets. Bitter melon is chilling sensitive, and not recommended for storage below 7°C. However, the consignment in truck 1 was stored at 3–4°C for several days. Despite this, the outcome may still be better than product in truck 2, where temperatures fluctuated significantly with daytime temperatures. This suggests the truck cooling system was not adequate to cope with the load, and significant condensation inside the boxes would have resulted. In the case of truck 3, the load appears to have changed trucks at least once en route, and possibly twice.
Temperature monitoring can also help identify where problems may be occurring still on farm, or during sale. Product at the centre of a pallet failed to cool well after packing. Even after five days of cold storage a significant temperature difference remained between the inside and outside of the pallet. Although temperatures on the outside of the pallet warmed during loading onto the truck, the truck cooling system reduced temperature during transport. The truck cooling system was turned off several hours before delivery to the wholesaler. The product was then displayed on the floor of the wholesale market for two days. In between markets it was cooled to 5°C, but then immediately warmed again when returned to display. Such fluctuations are likely to increase disease development in packed product.
Identifying where breaks occur in the cool chain is the first step towards finding solutions.
Supply chain analysis
Clearly not all quality issues relate to temperature. Preharvest practices can have a significant impact on postharvest quality, particularly in relation to harvest maturity. Damage can also be caused by harvest, packing or transport practices, use of inappropriate packing materials or mismanagement during storage.
If an issue is identified at wholesale or retail, a supply chain analysis can determine where damage is occurring. This usually involves sampling the product at each step of the chain to examine where damage is most likely. If, for example, rots were identified as a significant issue for pumpkin at retail sale, samples of pumpkins could be examined for signs of damage immediately after harvest, after transport to the packhouse, following packing into bins and after transport to wholesale market or retail distribution centre.
If it was identified that injuries were occurring at the packhouse, then the line could be examined in more detail to determine how this was occurring. One way to check for impacts is using an ‘instrumented sphere’. This records impacts as it is processed down a packing line. Spheres are available in different sizes to simulate a range of products.
Another method is to use a ‘shock logger’. These record impacts using built- in, three-dimensional accelerometers. As with temperature loggers, these are increasingly affordable and easy to use.
Combined with visual assessments, such devices can help identify where injury is occurring. Simple measures—such as adding extra foam padding on a packing line—can then be used to mitigate damage.