Thursday, December 9, 2010

Focus on.... Product Respiration

This week's blog post focuses on one segment of UWC's document entitled Interactions between Refrigerated Trailers and Product. Product respiration is a crucial factor at work in any perishable load, and its actions influence fruit and vegetables products upon delivery.

What is Respiration?
Respiration is the process by which plants take in oxygen and give out carbon dioxide. In basic terms, the oxygen from the air breaks down the carbohydrates in the produce into carbon dioxide and water, and this reaction produces energy in the form of heat.

Effects product temperature can have on loading:
A refrigeration unit is not designed in any way to cool product; it is designed only to maintain the load temperature of a product. Even state of the art technology in refrigeration can only "chill" product 2 degrees F every 24 hours.

Further, if the trailer is set to a very low temperature in an attempt to cool product at a faster rate than mentioned above, the unit can "freeze up" and this will inhibit the ability to maintain the desired temperature after the product is loaded on the trailer. Or, if a shipper loads "hot product" on the trailer, the moisture created can cause the unit to not cycle properly.

Heat and Respiration
There are two sources of load based (or product based) heat: Sensible heat and vital heat. Sensible heat is also referred to as retained heat and is the amount of heat above the desired transit temperature in products and packages. Vital heat is generated by the respiratory activity of products like fruit, vegetables, and flowers.

As outlined above, respiration is a major factor at work in each and every produce load; it must be taken into account when loading product, and when evaluating product upon delivery. If the product pulps hot or cold upon loading, this will affect the rate of respiration of the product, and therefore the ambient temperature inside the trailer.

To view the complete document, please visit, and navigate to the Customer or Carrier Online Forms!!!

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