forwarder facility. The temperature was 92 °F that day. You
might remember the Escherichia coli outbreak in bagged spinach
a few years back. Bacteria grow rapidly in enclosed, warm,
moist environments like plastic bags. If this shipment were contaminated, it is likely that many more people would get sick
than if the temperature were carefully controlled.
Reefer Temperature Variation
Take a look at Figure 2 below. This is a temperature profile
of the pallets in a trailer. The number 1 along the bottom of the
scale shows the location of pallet 1. Pallet 11 is on the right.
Blue pallets are on the right side of the trailer, red on the left. It
doesn’t take much to realize that product in the middle of the
trailer is hotter than product at either end or that there is fairly
significant variation throughout the trailer load. Reefer temperature variation is a manageable trucking problem.
Figure 2: Reefer Temperature Variation
Pallet Loading and Routing
Figure 3 shows two rows of pallets, six pallets in each row.
The colors depict remaining shelf life based on temperature
controls. Pallet Row 1 (Figure 3, top) shows a lot of color (tem-
perature) variety. This is a normal trucking setup where the
grower unknowingly mixed warmer produce with produce that
had been properly precooled and managed to deliver consistent
quality. This is a typical first-in-first-out scenario. The distribu-
tor receiving produce on each pallet would probably break
down the pallet contents for delivery to retail outlets or restau-
rants. The customer receiving short-shelf-life produce might
have something unacceptable to say to the trucking company
that delivered the produce.
If we backtrack to the farm, it is important to note whether
produce goes through a precool operation. Precooling generally
involves a tunnel filled with gaseous coolant (e.g., nitrogen).
Pallets or bins of recently harvested produce are put into the
tunnel, the tunnel is cooled with the gas and then a tempera-
ture reading shows. There is ample data to suggest that the
problem is that the middle of the bins or pallets generally can-
not precool properly. Field and environmental heat is thereby
trapped in the middle of the load. When the load goes into the
trailer, this heat migrates out over time and results in a warming
trailer. Both the produce’s and the trailer’s am-
bient temperatures rise, resulting in shortened
shelf life, returns, rejects and lower yields.
Figure 3: Pallet Rows Showing Shelf Life Remaining Based on Temperature
Technology Offers Solutions
A few years back, neither the technology nor
the data existed to help food and other supply
chain players get better control over transportation processes. Intelligent routing for tempera-ture-sensitive products (e.g., produce, frozen
goods, pharmaceuticals, etc.) wasn’t well understood, and neither were shelf life, yield or FEFO
The recent passage of the Food Safety Modernization Act will require all food supply chain
players to step up and prove they can deliver
safe quality rather than plaster “quality” slogans
all over their advertising. Plastic pallets with