Proper temperature, proper humidity
Treated properly, fresh produce maintains its quality and appearance from harvest to consumption. While transportation takes only a few days in produce shelf life that can be as long as a month or more, handling during transit plays a critical role in allowing optimum product life. For instance, allowing some stone fruit to warm up 30% above the recommended transit and storage temperature can cut shelf life by half. Allowing ethylene-sensitive produce to come into contact with fruit or vegetables that produce high volumes of ethylene as they ripen accelerates ripening of the sensitive produce, cutting its potential shelf life.
Plant tissue begins losing moisture immediately after harvest, especially through cut surfaces. Maintaining high humidity levels during transit helps slow this process. Unfortunately, the heating and cooling inherent in the normal refrigeration cycle accelerates this process. Refrigeration unit manufacturers have made great strides in recent years to reduce temperature variation and slow the amount of moisture pulled from produce during transit. Humidity control can be enhanced by topping loads with a shallow layer of ice where appropriate.
In general, shippers and receivers know their products well and take appropriate measures to maintain the best possible transportation environment. Carriers have a responsibility to assist in this effort by providing clean, well-maintained equipment, properly serviced and fueled, ready to roll. In addition, drivers should carry a thermometer so they can verify that product temperature loaded in a trailer matches that specified on the shipping papers. Thermometers need not be elaborate, but they must be accurate. Sticking a thermometer in a container filled mostly with ice along with some water and verifying that it reads 32°F should be sufficient to judge accuracy.
Drivers with produce experience usually are expert at handling it. However, truckload fleets have a constant need for new drivers, some of whom may be unfamiliar with proper care of fresh produce. The following table provides a quick guide to proper temperature requirements, icing options, and sensitivity to ripening gases.
