Some methods to prevent abuses in the cold chain are:
Explore this issueAugust/September 2007
Supply chain managers today use several low technology approaches that are popular and effective at extending the life of refrigerated products.
One method is pre-cooling, in which a product is brought to a lower temperature by producers prior to loading into refrigerated containers. Pre-cooling removes latent heat and effectively extends product life. The transport refrigerator is not designed to remove excess heat from a pre-cooled load but rather to maintain an acceptable temperature range. Pre-cooling also reduces moisture that would otherwise be present, which keeps shipping cartons dry and strong, and—in the case of fresh foods—prevents unwanted microbial growth. Many producers use drying/chilling processes to effectively remove moisture as a product is cooled.
During the loading of refrigerated pallets, placing products properly by creating gaps between pallet rows allows refrigerated air to circulate freely through the load. Many refrigerator units blow air out of a single duct from the top front of the container, across the tops of the pallets. Tightly packed pallets refrigerated in this way suffer from a false floor: air above the pallets is the proper temperature, but the temperature remains elevated down in the load. Some refrigerated containers feature air ducts for distribution of supply air and return air down the sides of the space, which helps to equalize temperature. Cartons with air ventilation holes in the side panels also promote good air circulation in the pallet and reduce the possibility for condensation around or on the product.
Take precautions during loading and unloading to prevent refrigerated product from becoming exposed to non-refrigerated air temperatures (as is the case in the shipment temperature example in Figure 2). Avoid placing refrigerated pallets on an open shipping dock for any period of time — especially when product is changing hands. This happens when, for example, a truck is unloaded, the shipment is signed for, and the driver leaves. Then perhaps the dock crew breaks for lunch or a shift change. When such events occur, the producer/owner of the product rarely has visibility as to the problem until the later point of pain (e.g., when the retailer returns the product or when the consumer rejects it as second rate or spoiled).
To gain visibility into the cold chain, many supply chain quality assurance (QA) managers require that one or more temperature monitors be included with each container shipment. They typically request that the device or its data be returned from the destination. These monitoring devices are referred to as temperature data loggers or temperature data recorders. They can be electronic or mechanical.
Mechanical recorders, such as the Ryan recorder, save a basic temperature history on a strip chart. Electronic data loggers take more accurate periodic temperature readings and store them in memory. One or two monitors per load are typically placed on top of pallets or attached to the sides.
Examples of these types of products include those from Cargo Data Management Corp. (Irving, Texas), DeltaTRAK Inc. (Pleasanton, Calif.), Pace Scientific Inc.(Mooresville, N.C.), HOBO (Bourne, Mass.), and Sensitech (Beverly, Mass.). They typically share the following properties:
- Cost $15 to $175 each;
- Must be programmed prior to use to establish upper and lower temperature set-points, periodicity, and other variables;
- Are reuseable/rechargeable; and
- Send data from a destination point to the owner’s QA contact.
Newer monitoring devices feature active radio frequency identification (RFID) technology, which allows a wireless data link to be established directly between the product and local readers. Some devices track temperature and upload it upon reading. These incorporate a battery and cost $22 to $250 each. A growing list of companies, including Sensitech and Intermec (Everett, Wash.) offer such products. As for active RFID readers, some are handheld and others are mounted on conveying systems or product portals. When a tagged product passes a reader, product data are read.