Temperature Monitoring During the Management of Perishable Products

When transporting fresh food, it is becoming increasingly important to record the temperature and, in some cases, the humidity to which goods are exposed. This white paper provides background information on temperature and humidity recording in logistics and describes equipment options. After reading this document, readers should understand why they need access to temperature and humidity data, the equipment available and how to use them.

Background on temperature monitoring

Many products degrade quickly at room temperature and more quickly at high temperatures. Food products such as fruit, meat and fish will not be able to be shipped long distances without refrigeration. Cooling to 13°C (55°F) may be sufficient to sell products such as bananas fresh (or not frozen immediately). Eggs are another example that also require humidity control. Other products need to be frozen to prevent spoilage. The same applies to many medications and medical devices. The Association for Healthcare Distribution Management estimates that about 10% of medications are temperature sensitive. Vaccines and blood products are other examples of medical devices that require tight temperature control but can be freeze-dried during the freeze-drying process.

The need for temperature control goes beyond human consumption. Certain special paints or coatings can be damaged at low temperatures. Other chemicals must be kept within strict temperature limits during transport.

Another area is the transportation of antiques and artwork. Humidity can be a bigger problem than temperature, especially because the combination of the two can lead to mold.

Cryogenic transport systems (for fresh food)

The temperature of fresh products must be kept under control from the point of origin to the point of delivery to the retailer or pharmacy. In the logistics industry, this is known as the "cold chain" and includes not only "refrigerated containers" (reefer containers), but also warehouses, distribution centers and, ultimately, storage and storage locations.

There is always a risk of failure in this chain. This means that even within a short period of time, charging can exceed acceptable or safe temperatures. For example, desert heat could cause a truck to stop and, without power, the temperature in a refrigerated container would rise. Power would then be restored and the temperature in the container would drop, but the product would be damaged.

Cost and liability issues

These shipments may be damaged if exposed to temperatures outside the specified range. In the case of bananas, for example, this may be obvious, but in other cases, such as the shipment of vaccines, the damage may not be obvious and the vaccines may be ineffective. For some products, even moments above temperature can significantly shorten their shelf life and result in considerable costs if they are not offered for sale.

The company shipping the contract product will usually report an acceptable temperature range. Even though this may indicate that the product was affected by conditions other than the terms of the contract, it is difficult to prove where this occurred and therefore liability. The answer is to record the temperatures experienced based on time.

Temperature and humidity records

The maximum and minimum thermometer was invented around 1780 and has long been the only way to record the maximum and minimum temperatures observed during a given period of time. Besides the use of mercury as an expansion medium, another disadvantage was the lack of time measurements. As a result, such thermometers could be included in fruit shipments, but there was no way to know when or for how long the peak temperature was reached. Without this information, it is difficult to determine responsibility for spoilage.

The same is true for humidity displays. There are several types available, most of which use a color change effect to display peak or current humidity. However, as with the maximum-minimum thermometer, there is no time record to ignore.