Does a controlled atmosphere during transit with a high concentration of carbon dioxide, such as found in the Tectrol system from TransFresh Corp., help reduce the incidence of decay in strawberries?

The answer is yes, according to Elizabeth (Beth) Mitcham, a researcher at the University of California-Davis Department of Plant Science and director of the UC-Davis Post Harvest Technology Center.

Elizabeth (Beth) MitchamAlthough there are people who question the benefits of a CO2-enhanced atmosphere, Mitcham bases her conclusion on the results of a carefully designed two-year study of pallets of fresh strawberries shipped cross-country, conducted by the University of California-Davis and Florida State University, in which she was involved.

The reduced incidence of decay is not manifest upon arrival of the product when it has been held between 32 and 39 degrees Fahrenheit during transit, but becomes evident two or three days later, after the fruit has been sitting out at 65 degrees as it might on a retail shelf.

The Produce News had the opportunity to discuss the study and its results with Mitcham and Rich Macleod, vice president of the TransFresh Pallet Division, in a conference call.

According to Mitcham, the study demonstrated two potential benefits of using pallet covers with strawberry shipments. “One is reducing water loss and keeping high humidity,” and all pallet cover systems evaluated proved beneficial in that regard. “The other is reducing decay,” and that is only achieved with high concentrations of CO2. Of the systems evaluated in the study, “only the Tectrol did a significant job of modifying the CO2 levels,” thus providing “an extra benefit” over the other systems.

Mitcham, who has been involved in controlled atmosphere research for more than two decades, emphasized the meticulous manner which the study was designed and carried out. “We put the study together very carefully,” she said. Several pallet bag systems and an uncovered pallet as a control were compared and evaluated “six different times over a period of two years.” The berries all came into the cooler from the same field. They were “randomized” so that each pallet had the same quality of berries that had been handled in the same way. The pallets were fitted with temperature sensors, then the pallet covers were applied and CO2 and oxygen levels were checked before shipment.

When the shipments arrived on the East Coast four days later, “we had a team of collaborators from [the University of] Florida” who received and evaluated the shipments, giving the berries “a thorough evaluation both immediately and then after a period of time,” she said. ”This included a sensory evaluation” for flavor, quality and texture, a measurement of water loss in the fruit, and a measurement of the extent of decay.

“It was a very well designed and objective experiment, comparing these different pallet covers in an attempt to determine which pallet covers gave the best quality on arrival and then after simulated retail handling,” Mitcham said. “One of the real benefits of university research to the industry is the objective way that the information is collected.” By going to “that level of effort … you can actually trust the results that come out the other end.”

The “most obvious observation” in the study is that none of the pallet cover systems “modified the atmosphere to any significant extent at all except Tectrol,” although one system utilizing CO2-emitting pads did elevate CO2 levels slightly resulting in “a little bit of decay control,” she said. “But in terms of the atmosphere modification, the Tectrol system worked the best.”

All of the covers reduced water loss in the product, Mitcham said, “so having a cover is better than not having a cover.” But only a “true modified atmosphere,” as in the Tectrol system, was shown to have “benefits in terms of decay control.”

Sensory quality of the berries was not found to be influenced either beneficially or otherwise by any of the pallet cover systems, she said.

Macleod commented that benefits achieved by Tectrol in the study were clearly a function of a combination of factors. “You have to have a bag, you have to have it sealed, and you have to inject and then control the right mixture inside that sealed system so you have a benefit to the product. In our case, the active ingredient is carbon dioxide. In this study, the only product that was sealed and maintained any semblance of CO2 concentration was the Tectrol product.”

The complete study, as published in Hort Technology August 2012 is available from the TransFresh Resource Library accessible on the TransFresh website.