Friday, September 8, 2017

Precooling as an industry

The term “precooling” refers to the treatment of produce to get its temperature down to the desired shipping temperature prior to loading for transportation. It applies to any mode of transport, whether highway trucks or railroad cars, but naturally I am interested here in the rail side of it. In particular, I want to talk about how this might be represented on a model railroad.
     [I should point out that an ice refrigerator car, supplied empty to a shipper but with ice in the bunkers, has not been “precooled,” it has been “pre-iced.” In other words, cars are pre-iced and produce is pre-cooled, not the other way around. That was the language in the perishable tariffs, and it seems to me appropriate that modelers use the same terminology.]
     Up until about World War II, normal practice in produce shipping was to load produce into reefers at ambient temperature, even if still warm from the field or orchard. Then the load would gradually cool in transit, with the absorbed heat melting the ice, and calling for a substantial re-icing within 24 hours. This mostly worked, but it meant that produce was above shipping temperature for some hours, and more seriously, all parts of the load inside a car of, say, 462 crates of oranges would not cool equally quickly.
     Starting in the 1930s, the USDA (U.S. Dept. of Agriculture), and also perishable car companies such as PFE, recommended to growers that they invest in pre-cooling, and thereby gain control over these potential temperature variations. They would thus achieve more consistent shipping conditions, leading of course to more consistent condition of the produce on delivery. Pre-cooling by growers steadily increased, and was widespread by the early 1950s. But an alternative to the grower doing the pre-cooling, was to pay a pre-cooling company to do it for them. That is the topic of this post.
     Precooling methods were described in some detail in the PFE book (Pacific Fruit Express, 2nd edition, Anthony Thompson, Robert Church and Bruce Jones, Signature Press, 2000, still in print as of this writing), so I will only summarize here. The simplest precooling process was simply to put the produce in a refrigerated room, in which the filled shipping boxes could be stored until cool. More rapid precooling of dense, convex products like citrus, apples or melons could be achieved by immersing them in running cold water. For leafy vegetables such as spinach or lettuce, vacuum precooling is effective. In this method, the produce is misted with water, then exposed to a partial vacuum, which very rapidly evaporates the water, with attendant cooling.
     Now I want to turn to pre-cooling as a separate business. I will begin with a specific company, Guadalupe Cooling, which I wrote about in a prior post (see it at: ). This company post-dates significant rail shipping of produce from this area, but happens to be located quite near the former SP Coast Line tracks (now UP). The sign at their gate on the highway looks like this:

(Guadalupe Road is California Highway 1 in this area.) Like the half-dozen or so other precoolers in the area, they offer warehouse cold-storage space as well as precooling service, and the various growers who use the facility can then ship directly from there. There are 15 or 20 truck loading bays at the facility, so this is not a small operation.
     For layout design, this means that a pre-cooling operation would be a significant source of refrigerator car traffic, and moreover that waybills would identify a wide range of individual growers who would ship from the pre-cooler, taking advantage of the pre-cooler’s warehouse space. If the pre-cooler operates as a forwarding operation, however, the waybills would show the pre-cooler as the shipper. If a Shipper Guide is available for the railroad of interest, it could be determined whether the shipments would originate from growers or from the pre-cooler. Such a Guide shows shippers, so would make this distinction.
     One reason I have been thinking about this topic is that one of the packing houses on my layout, Guadalupe Fruit Company, handles tree fruit, and accordingly only actively ships during part of the year, even if I add early spring strawberries. But if the facility became a pre-cooling company instead of a packing house, I could ship practically year-round, because the vegetable crops in the area I model are indeed harvested all through the year.
     I could even be more flexible than that. I could make a stick-on sign for Guadalupe Cooling, simply taken from the image of the prototype sign you see above, and attach it atop the existing sign on Guadalupe Fruit Co., whenever we are outside the tree fruit and strawberry seasons. Here is the existing sign on the building (I showed this photograph in a prior post: ).

Since this photo was taken, I have added a decorative parapet around the top (you can see that post at: ). Since the sign is framed, it would be easy to insert a same-size sign atop it, with, say, Post-It adhesive. I am thinking about this option.
     For any area that ships produce, a pre-cooling company is a very flexible kind of shipper, being capable of handling a range of produce, and will also ship in larger volume than most individual packing houses. It is worth considering if you are looking for more produce shipping.
Tony Thompson

No comments:

Post a Comment