Sargent
For small farmers, delivering fresh, high-quality produce to markets can be quite a challenge. So many factors involved with harvesting, handling, packaging, transportation and storage are the reasons that some operations cease to expand sales. Temperature, especially in Florida, is a major challenge that growers face.
Steve Sargent, post-harvest Extension specialist in the horticultural sciences department at the University of Florida, presented research-based advice to a group of growers at a recent agricultural workshop. He has researched ways to minimize the pains of spoilage, waste and loss of revenue in leafy greens.
According to Sargent’s research, upon harvest, products should be cooled to their optimum storage temperature range as quickly as possible for optimum post-harvest quality.
Examples of room cooling versus rapid cooling at the demonstration given by Sargent.
“Temperature management is really important,” Sargent said, “The importance is in taking a crop, and as soon after harvesting as possible, getting it to a condition where it’s ready to sell. Not only ready to sell with high-quality, but having the ability to maintain that quality over time.”
Sargent gave examples of ways (room cooling, forced-air cooling and hydrocooling)to cool produce such as lettuce, basil and Asian vegetables that are primarily used in stir-fries and salads.
According to the research, room cooling involves placing produce in an insulated room that is refrigerated to a desired temperature. This form of cooling can be used for any commodity. However, room cooling is best for relatively non-perishable commodities and for when marketing is rapid.
Forced-air cooling is used in conjunction with a refrigerated room and can be very effective for rapidly cooling most packaged produce. In contrast to room cooling, in which cool air circulates around containers or pallets of produce, in forced-air cooling the cool air is drawn through the packages and thus comes in direct contact with the produce within the packages.
Hydrocooling is basically submerging the produce in chilled water. Sargent said that just about all crops can tolerate temperatures down to 32 degrees Fahrenheit, which will hydrate them.
Hydrocooling of lettuce
Sargent explained that rapid cooling can be effectively achieved “using something as simple as a cold room with high-velocity air blowing around in the room to cool the product quickly, or immersing it in ice water to cool it very quickly and also minimize water loss, which is a problem with leafy vegetables.”
With regard to refrigerated storage, small window air conditioning units are relatively inexpensive. Therefore, small-scale producers may find it advantageous to purchase a window unit and retrofit it into their storage facilities. Window units can be used in a variety of buildings such as insulated storage sheds or garages, marine cargo containers or other similar facilities. Additionally, moisture loss can be mitigated by placing plastic liners over stacked boxes of product.
Sargent cautions that while changes in temperature will affect the respiration rates of fruits and vegetables, extreme temperatures can also cause physiological damage to fresh horticultural products, depending on the commodity. Direct contact with ice can be severely detrimental to some produce, so research the best cooling techniques before testing them on your own produce.
More information from Sargent’s research can be found online at Postharvest Storage, Packaging and Handling of Specialty Crops: A Guide for Florida Small Farm Producers.
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