Trailer refrigeration is one of, if not, the most important factor in ensuring the delivery success of fresh fruits and vegetables. The object of trailer refrigeration is to prolong storage and shelf life, and to maintain quality by lowering the commodity temperature so that respiration, metabolic deterioration, and decay are slowed down. One of the most important things to remember is that the function of a trailer’s refrigeration unit is to maintain the temperature of the commodity, not to lower the temperature; therefore, pre-cooling of fruits and vegetables prior to shipping is essential.
So now, let’s look at some of the key factors in trailer refrigeration.
Methods of refrigeration
1. Mechanical refrigeration: this operates by absorbing heat at one point and dispensing it at another. This is accomplished by circulating a refrigerant, most commonly Freon, between two points.
2. Ice: in addition to mechanical refrigeration, ice is sometimes used to help maintain humidity inside the trailer. The main drawbacks for ice are its weight which cuts down the allowable product weight, the arranging of replenishing ice while in transit, and the requirement of water-resistant shipping containers. Recommended procedure for top icing is to apply the crushed ice on top of the load in 3 length-wise windrows. The thermostat should be set to 35F to allow the ice to melt steadily during the trip; a colder setting may crust or freeze the ice and block air circulation, which then affects trailer air circulation and causes heat to build up in the interior of the load.
Air Circulation
Air circulation is critical to ensure uniform temperatures throughout the load. There are two methods of circulating air in refrigerated trailers:
1. Top Air Delivery: This is the most common design in trailers. Ceiling ducts are used to direct the air from the blower to the rear of the trailer. Load patterns that provide unblocked air channels throughout the load to allow the air to return to the blower intake are required. Load locks must also be used to prevent the load from shifting or toppling backwards and blocking air circulation between the load and the rear doors. Recessed groove floors and inverted-rib sidewalls are also designed to increase the amount of air that can be circulated through the load. Finally, bulkheads are designed so they do not block the air returning to the blower.
2. Bottom Forced-Air Delivery: In this method, air is forced under and up through the load. The air returns to the lower over the top of the load and through the top of the bulkhead.
Humidity
Most fruits and vegetables require high relative humidity to prevent dehydration and to keep them looking fresh and crisp. Some moisture loss during transit has to be accepted, but it must always be minimized, by the following procedures:
1. Using top or packing ice where possible.
2. Thorough pre-cooling to reduce the temperature difference between the product and the surrounding air.
3. Keeping the refrigeration unit’s coil only a few degrees colder than the desired transit temperature.
4. Waxing or using semi-permeable wraps to reduce evaporation.
Do you have expertise in trailer refrigeration? Please share! Also have a look at some of our numerous posts that discuss the popular topics of temperature, loading/load compatibility, and how a refrigeration unit works!!!!
References:
Transportation. RBCS Handbooks. http://rbcs.com/HandbookArticles/transpor.htm. Accessed on Nov 3, 2011.
Yesterday, UWC had our 2nd Annual Pumpkin Carving Contests. Teams of 3 or 4 were randomly selected, and 8 pumpkins in total were carved! At the end of the day, a vote was taken. Below, the pumpkin of the winning team, yoU Will Cry:
Great pumpkin team, and great name too!!!! Head over to our facebook page to see all 8 great pumpkins!!! Hope everyone had a safe and fun Halloween!
The produce industry has celebrated the news that Mexico has officially lifted tariffs that have amounted to more than $900 million of US agricultural products since 2009; this helps to settle a costly dispute over the Mexican trucking pilot program. We discussed this topic back in a post in April; as a review, Mexico is the United States third largest trading partner, and the Mexican tariffs were imposed after years of disputes over a provision in the NAFTA that allowed Mexican long haul trucker to enter US highways in 2000. When US congress blocked funding for the program, the dispute was set into motion.
The first Mexican truck crossed the US border on Friday, Oct 21, 2011 as part of the new cross-border trucking pilot program between the Mexico and the United States. The truck crossed the Rio Grande at the Laredo point of entry, and was bound for Garland, TX. Earlier that Friday, Mexico lifted the remaining tariffs on 99 U.S. products that are exported to Mexico.
With this new pilot program, Mexican approved carriers will be able to operate in the United States for up to 3 years, and similarly, US carriers can operate throughout Mexico for the same time period.
This momentous event means that for many US growers, a greater opportunity for increase in volume exports, and possibly product price increases.
Have any comments on the new pilot program and the elimination of the tariffs? Please share!
References:
Mexico Drops Tariffs as first Mexican Truck Roll over to US border. http://theproducenews.com/index.php?option=com_content&view=article&id=33163:mexico-drops-tariffs-as-first-mexican-truck-roll-over-us-border&catid=43:featured&Itemid=41. Accessed on 10/27/2011.
In other news….
Survey Says…
The 2011 ‘Jerry Maguire says, “help us help you”’ Customer Survey, and the 2011 “comchek-ing in” Carrier Survey are now complete! The surveys ran from Sept 15th – Oct 15th, 2011, with prize draws occurring on Oct.20th, 2011. Two customer participants are now the lucky owners of Apple 8GB iPod Nanos, and four carrier participants won prizes of $50 cash vouchers!!! Congrats to all our winners!
UWC contracted out the services of Survey Monkey to conduct these blinded and confidential surveys. Thanks to all who participated; the results have given us great insight on how we can serve our partners better!!!
Phantom Produce!!
Halloween is almost here, and to celebrate, we are having our 2nd annual office pumpkin carving contest. Stay tuned next week to see the winner!!!!
October: the start of Fall, and for the refrigerated produce industry in North America, the time when produce starts transitioning to ship out new areas. UWC closely follows these transitioning trends, as it allows us to plan for lanes and anticipate truck demand. So, let’s look at 4 full truckload products and how they are transitioning.
Avocadoes: The season in California has concluded. Mexico inventories have been noted as lower due to heavy rains halting the harvest at the end of last week. Weather in this region has improved, and harvest should increase by the end of this week. In particular, movement from crossings through Texas are expected to increase.
Cucumbers: In the Baja, light production has continued throughout this week; many growers have moved through the flush of new field crop. Some early production has started out of mainland Mexico, with crossings through Nogales expected to increase seasonally, and crossings from Otay Mesa, CA expected to decrease slightly. Light shipments have also begun out of the Central and South Florida districts, with sufficient volume expected by the end of October.
Bell Peppers: The California Central Valley and Oxnard district crops are beginning seasonal decline, with overall volumes set to drop. Green bell peppers will begin out of the California Desert/Coachella Valley lightly starting next week. No real volume is expected until mid-November. The supplies of colored bells remains good, but are starting their seasonal decline. Mexico crossings through Arizona are expected to arrive the week of Oct 24th, with reportable volumes expected by mid-November.
Tomatoes: Growers and shippers in the San Joaquin Valley, California are in their last couple of weeks of harvest. Most product is still coming out of this area, along with the California Coast, and some Mexico Crossings through Otay Mesa, California. Demand is set to shift to the East by the end of October, with light harvesting set to start at that time in West and Central Florida.
Stay tuned for more news/transition updates!! Have any insight to share? What is the best way you plan for these transitions??
References:
The Packer – Crops and Markets. http://www.thepacker.com/fruit-vegetable-news/crops-markets. Accessed on Oct. 19, 2011.
Pro-Act; The Source Market Report. http://web1.digitalmotionsolutions.com/proactusa.com/PDF/The%20Source.pdf. Accessed on Oct. 19, 2011.
Temperature, Equipment, and Loading Procedures & Guidelines are topics that we revisit regularly here. One of the reasons why is that we recognize that these factors are critical to the successful delivery of any shipment, and we strive to constantly share our wealth of knowledge with our followers!!!
Today, let’s review some essential loading tips. More information on loading can be found in our Carrier Loading Guidelines, available for download off our website, and in hard-copy at TC Trans in Blaine, WA!!!
There are many points that must be checked before and during loading to make sure that the integrity of the refrigerated trailer is maintained. For example, high temperature in a refrigerated trailer can allow bacteria normally present in food items to increase to dangerous numbers.
Below, a checklist with some notable features that should be checked prior to loading (all noted in our Loading Guidelines):
Trailer container cooled to the recommended temperature?
Refrigeration unit operated correctly, and as designed?
Load thoroughly pre-cooled?
Load locks/bracing used to secure load? (check out our previous posts on this topic!)
Heating unit operates as designed?
Trailer aired to remove residual odors?
Temperature recorder working?
Air delivery chute intact?
Door seal undamaged?
Side door sealed tight?
Door, wall, or ceiling all undamaged?
Floor clean and undamaged?
Floor drains open and clean?
Front air bulkhead installed?
Inside height/width adequate for load?
Door height adequate for load?
There are some other helpful tips to keep in mind when loading:
- If the loading area is unrefrigerated, turn off the refrigeration unit while loading. Warm air drawn in during loading can cause the evaporator to frost, and will result in the refrigeration unit not being able to operate as designed.
- Avoid loading tightly against flat side walls by using pallets, racks, and dunnage. Room for air circulation must be provided under, around, and through the load.
- Do not block air circulation at the rear door.
Have any other tips you want to share? Please leave us a comment!
Now a part of the less than 1% club, UWC is TIA $100,000 Performance Certified!!!! Click here to read more!
References:
The Packer. The Guide 2011: Produce Availability & Merchandising Guide. Vol CXVIII. No. 54.
