Dry ice in the containers results in better quality red fruits
Transportation and quality are often a challenging combination. A good product can arrive in Europe as a poor quality product after several weeks at sea. Several options can be used to preserve product quality, and Wageningen Food & Biobased Research has recently added a new option: dry ice as a source of high levels of CO2 for the transport and storage of berries. Now a partner is needed to market the product.
“We wanted to create a high CO2 content in the shipping container, reefer container or truck to protect the product against spoilage,” says Eelke Westra, postharvest technology researcher at Wageningen Food & Biobased Research. We are looking for an alternative to SO2, CO2, for which we are also looking for a way to easily maintain it in a high concentration with the use of dry ice. It is mainly about protecting against mold or other quality defects that can be prevented with a high level of CO2″.
High content of CO2 as an alternative to SO2
The Dutch research team responded to the demands of an alternative to CO2 for the market. To transport grapes, increasing the CO2 in the container is relevant to combat the Botrytis. “SO2-impregnated pads are used for that purpose, but there is a possibility that Europe will ban their use. Also, some people are allergic. It is for these reasons that we received the request for an alternative,” says Eelke. Another disadvantage of SO2 pads: when the dose is too high, the fruits are damaged, as the fruit loses color. “That was the reason why we investigated the high CO2 content in the containers, and since we already knew that dry ice could be useful, we also took that into account during the study.”
The conventional method of creating a high level of CO2 in a vessel is to first use nitrogen to dissipate the oxygen, after which the CO2 expands in the vessel. The container must be made resistant to gases, "and we hope that the CO2 content in the container will remain high during the entire transport, since the containers do not have CO2 cylinders." The researchers chose to look for a source of CO2 in the container. “Products breathe, but not all products produce enough CO2, so a source is needed in the container,” Eelke explains. A CO2 cylinder could be one solution, but dry ice, the solid form of CO2, is another option. It is also an affordable option, estimated at around 200 to 400 euros per container.
Grapes, currants, cranberries ...
But what is the advantage of dry ice compared to a CO2 cylinder? “It can be put in the container at the beginning of the supply chain, so you don't have to wait for the container to get to where the cylinder is. Because of that, the trajectory with a high CO2 level is longer,” says Eelke. Also, the waterproofness of the container becomes less decisive. Containers are assumed to be airtight, but verified as standard. "We haven't investigated it either, but we do know that the desired CO2 concentrations are not always achieved," she continues.
Although the research was based on grapes, other products, such as currants and blueberries, are also transported using high levels of CO2. Some types of fruit respire more than others and emit a lot of CO2, being able to generate around 20 percent of the CO2 content that way. “The product produces its own CO2,” Eelke clarifies. Grapes and blueberries do not respire enough to reach a high percentage. "A controlled atmosphere container does not generate CO2, so an alternative source is needed."
“The study mainly focused on the technical aspect of keeping the CO2 level high for longer periods.” Depending on the amount of dry ice placed in the container, the container could have high CO2 levels for two to three weeks. The study was finished a year ago and a patent was applied for. “The grape importers we work with are primarily interested in quality,” concludes Eelke. “They won't market the product, but they do want to use it. The project is in a development stage and we are looking for market participants, such as logistics service providers, who want to work with us to commercialize the service”.
For more information:
eelke.westra@wur.nl
paul.goethals@wur.nl
www.wur.nl/wfbr
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