"Regarding location, there are two areas in a trailer that placing a temperature monitoring device (TMD) is not recommended. You never want to put it on the south-facing wall because the south wall is always warmer. The TMD is not going to give you an accurate reading in that location."
-Doug Thurston, Vice President Sales, Emerson
If you are just chiming in on this blog post, it is important to note that this is the second half of the two-part series, Myth or Fact? The Truth About Refrigerated Shipping. Part one can be found here.
Moderator: James Lee, Choptank Transport, Vice President of Legal Affairs
Expert Panelist Jeffrey K. Brecht: University of Florida, professor, and co-author of Protecting Perishable Food in Transport by Truck and Rail.
Expert Panelist Doug Thurston: Emerson, Vice President of Sales
Expert Panelist Greg Blades: Thermo King, General Manager
Myth or Fact #4: Is it okay to mix a load of products that have varying temperature requirements on the same truck? For example, fresh with frozen, dry with frozen, or dry with fresh.
Doug (Emerson): In most cases, it is simply not recommended. In the last 10 years, however, it has become somewhat of an industry-standard with a lot of the retail customers. They will do what we would call a 'mixed load' with variable temperature requirements on the same truck for fuel-efficiency. It can be done, but with one caveat. It must be done with the right type of trailer, such as a multi-temp trailer where you can validate temperatures throughout the load, making sure you are not damaging any of the product.
Years ago, retail delivery meant a straight load of produce that went to three or four stores. It was easy to manage temperatures. A lot of that changed after the last recession. Most retailers adopted the practice of doing mixed loads or combo loads. It saved them on the number of deliveries per store on a week-to-week basis, but what they didn't realize was how much they were challenging the integrity of all of those products. What they are saving in transportation costs, they may be actually losing in product quality and shrink.
The Effectiveness of Bulkheads
Moderator: Sometimes shippers will use bulkheads to separate fresh and frozen products. How reliable is that method of temperature separation and control? I've seen various types of bulkheads. I have even seen somebody put a piece of cardboard and say that it is a bulkhead. I also see people using thermal blankets to keep products from freezing.
Doug (Emerson): The bottom line is if you use a bulkhead, you need to make sure you are using the right equipment. Make sure it's in good working order and that it is installed correctly and not blocking the air chute.
Depending on the length of the trip and the product you're hauling, bulkheads might not be always advisable. One of the biggest challenges retailers face is the short window of time they have to transport their goods. Bananas, for example, are pre-ripened at their distribution centers, followed by a six to 15-hour haul to get to their various store destinations. The bananas can't get below 56 degrees or they will chill and turn gray, which is not appealing to consumers. If they are in a truck with other products that require colder temperatures, thermal blankets are sometimes used to keep the product from getting too cold. It can be challenging.
Moderator: If a shipper insists on mixing products of different temperature requirements on the same load, do you recommend the use of multiple TMDs?
Doug (Emerson): We try to always promote best practices and in the case of mixed loads, we would call for monitoring each section of that trailer. What matters most is the integrity of the product -- the quality of that product. If you are willing to roll the dice and put multiple temperature commodities on the same truck, using multiple TMDs in those areas is definitely recommended to make sure you maintain the desired temperatures for your customers.
Myth or Fact #5: It doesn't matter where the temperature monitoring device is located inside the trailer, correct?
Doug (Emerson): Wrong, the location actually matters a lot. TMDs are small, typically about the size of a deck of cards. A trailer is very large. While there are a lot of variables that can go wrong in a trailer, there are only a few things that can go wrong with a TMD, such as it gets run over, or the battery dies. In those two examples, it just doesn't work.
Regarding location, there are two areas in a trailer that placing a TMD is not recommended. You never want to put it on the south-facing wall because the south wall is always warmer. The TMD is not going to give you an accurate reading in that location and will show it a little warmer than it should be. Another area you do not want to place a TMD is on top of a pallet directly under the air chute. That will give you temperature readings colder than they might actually be.
A TMD is a tool, like every other tool used in receiving to determine the integrity of the shipment. It shouldn't be the only measurement used to verify temperatures, just like the data that comes from the reefer download shouldn't be the only measurement to determine the product's integrity. The receiver should always review the product by pulping it as well as making their visual inspection of it. It should be one part of a complete process. A TMD is a part of the process.
Jeff (Professor UF): The reality is that unless the TMD is within a carton within the load, it is measuring the air temperature. Air temperature can change much more quickly than any product temperature because of the high water content in foods. You can assess how much a rise in temperature affects the food by the recovery speed from that temperature spike. If it comes back down quite quickly, then probably the product was not actually warmed, it was just air temperature around it fluctuating. But, if it takes a long time to come back, that is an indication that the product probably actually was warmed, which becomes a food safety issue.
It seems nowadays that receivers are much more aware of temperature deviations, and may very well reject a load because of a spike in temperature when in many cases the product was probably not significantly affected.
Moderator Question: Let's say that the TMD shows some spikes, and we are concerned about it. We ask the carrier to go get a download of his reefer unit. What exactly are we looking for in the download?
Doug (Emerson): Well, You want to make sure that your comparable data is similar. If you're not seeing similar temperatures between the reefer unit readings and the TMD, you've got to look at a couple of things. The first question should be, where was the TMD located. Secondly, are all those best practices that we talked about earlier being followed? Is there a bulkhead that might be blocking airflow? What's the age of the trailer? Then ultimately, the receiver should be pulping the product to verify that the temps are within the range that is required.
Greg (Thermo King): The reefer unit has readings for supply air, or what we call return air, and it also reads a discharge air temperature. You don't want to see a difference in those two readings (of a minimum of 10 degrees), which means that the unit is working properly. It is also important to make sure your set point was entered correctly. The download will also tell you the mode of operation: whether it was cycle century or continuous, and you want to verify that everything was set properly to haul the particular load that you're working on. Then compare the reefer unit readings to your TMD and see how far off they are. If there's a huge difference, there may be multiple reasons adding up to why there is a difference.
Myth or fact #6: It's really not necessary to pulp the cargo product before and or during unloading.
Doug (Emerson): My advice is to always pulp the product. I would require it to be pulped prior to shipping, especially produce, and at receiving.
Moderator: Whose responsibility is it to ensure the proper temp?
Doug: The product is owned by the shipper until the product is shipped. And if it is a meat or seafood load, they own it until it's delivered. So that falls on the shoulders of the shipper.
Moderator: So let's talk about the proper way to pulp. Can we use a simple digital laser gun, or do we actually probe the product itself?
Jeff (Professor UF): Yes, I would always recommend probing the product itself. The infrared thermometers are only reading the surface temperature, and you can definitely get the wrong impression of what the product temperature is by doing that. In many cases, you need to open up a package and probe the product, which may require you to remove it so that the customer doesn't find something with a hole in it and complain. Unfortunately, that's what you need to do to get the information you need.
Moderator: Lastly, how important is it to use checklists, standard operating procedures, and protocols for cold shipping?
Doug (Emerson): Best practices should always be applied. We have a checklist that we provide at Emerson for our customers or anybody that would like to have it. It takes you through the entire process. If you're looking for help from the grower-shipper side, to loading the trucks, to proper handling and transit, to cross-docking or cold storage facilities.
Jeff (Professor UF): Every shipper, carrier, and person involved in the supply chain should be aware of the Food Safety Modernization Act (FSMA). Anyone handling perishable products should have a set of standard operating procedures. Shippers and receivers should be sharing these procedures with each other. That way everyone knows what's being done to ensure best practices are being followed. These guidelines should identify what's expected of each stakeholder.
Get the Protecting Perishable Foods During Transport by Truck and Rail handbook here.
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