Keeping up with the cold chain

Features - Equipment & Technology

New methods for removing heat from produce and packaging is extending the shelf life of fresh greens and other produce.

March 1, 2018

Photo courtesy of lef farms

Growing the highest-quality product is the first order of business in any greenhouse food production facility. However, what happens during the postharvest cold chain period is what will ensure the product will end up on the dinner table as fresh as the day it was picked. New methods for removing heat from produce and packaging is extending the shelf life of fresh greens and other produce.

Leading the way at lef Farms

lef Farms, a company that opened in 2016 in Loudon, N.H., is supplying fresh, hydroponically grown greens to an increasingly larger base of customers in New England. It is owned by Pleasant View Gardens, a company that has been selling ornamental plants for about 40 years. The company’s president and CEO, Henry Huntington, had been looking for a way to diversify when he went into the produce-growing business, says Bob LaDue, VP and COO, a former greenhouse consultant and Cornell-educated horticulturist. Instead of using existing facilities at Pleasant View, they constructed a 75,000-square-foot standalone growing facility with a cooler big enough to handle any future plans of expansion.

Now, lef Farms has found a way to approximately double the shelf life of its lettuce, Pak choi and other greens. This is allowing the company to expand its market to all of the New England states and New York, according to Donald “DJ” Grandmaison, sales and marketing manager at lef Farms.

LaDue and Huntington have examined the cold chain methods growers have used over the years. They have helped lef Farms come up with some innovations in chilling and packaging that LaDue says are “game-changer[s].”

Photo courtesy of lef farms
Photo courtesy of lef farms
Photo courtesy of lef Farms

“A lot of what I was seeing was people harvesting these products either in a greenhouse or head house at the temperature they were growing,” LaDue says. “Then [they were] putting it in a plastic bag or clam shell — some type of container — and then putting those in a box, sealing the box up, palletizing them, wrapping them up in shrink wrap and putting it in the cooler to cool off.” The product would then end up in a cooler waiting for pickup; the insulation in the packaging would do an effective, but unfortunately counterintuitive, job of trapping warm air inside the packaging.

“Some of my work at Cornell was to put temperature-recording devices inside the packaging, then pack them in the core of the pallet and put them in the cooler,” says LaDue, who managed a greenhouse growing operation at the university for 13 years. “We found out it could take several days for the products in the middle of the pallet to get cooled to the proper temperature. Meanwhile, you’ve lost a lot of shelf-life potential.”

LaDue says when the greens are cut in the dark, they still go through the process of respiration, consuming oxygen and releasing carbon dioxide. This normal cycle is what leads to eventual spoilage. This process can be slowed down by keeping the temperature cool around the product while still allowing respiration to take place.

“We want to keep that environment around the leaves balanced to a normal oxygen/carbon dioxide ratio,” LaDue says. “We looked at a lot of different options. Instead of packaging in the head house, we would conveyor the raw product into the cooler, cut it, mix it, weigh it, bag it and palletize it; it was quite different from anything that was being done anywhere worldwide.”

The company also looked at every aspect of the way the product was being packaged before it shipped. He said they worked with a packager to come up with a laser-perforated packaging that allows for this normal exchange of gases. They also box up the greens in boxes that are more open than traditional boxes. And instead of securing all of the boxes on the pallet with a thick shrink wrap, they use a thinner wrap that he says “spider webs” around the boxes, keeping them from falling off the pallet, but also allows for necessary air flow.

LaDue says the product takes about five minutes from the time it is cut until it is bagged and ready to ship. It is then moved on pallets into a sealed chamber and onto a truck, thus avoiding shocking the product.

“We’ve really gone a long way towards quickly and effectively getting rid of the heat from the crop, and it’s working really well,” he says. (Editor's note: Read more about the operation here)

Photo courtesy of lef Farms
Photo courtesy of lef Farms

Keeping it fresh at NatureFresh

NatureFresh Farms, purveyors of greenhouse bell peppers, cucumbers and tomatoes, has also made a sizable investment in a heat-reducing storage facility, in addition to technology to provide computerized labor management. These investments allow the company to manage both labor and cooling.

Founded in 1999, NatureFresh is a well-known grower in the industry who supplies fresh produce to all of Canada and as far south as Florida and Texas as well as the Central and Eastern U.S. Each year, they trial over 300 varieties of vegetables, selecting the ones they feel have the best flavor and shipping quality.

“All our commodities are consolidated within our new modern distribution center we officially opened in August 2017,” says Ray Wowryk, director of business development at NatureFresh, based in Leamington, Ontario, Canada. He says that the facility is equipped with advanced high-efficiency pre-coolers that remove heat prior to packaging or market distribution.

“Precooling is key to maximize shelf life,” Wowryk says. “Providing ideal storage commodity-specific temperature and humidity is key also.”

The company utilizes technology to monitor the state-of-the-art packaging and storage facilities they invested in.

“Adding modern equipment and updating packaging machines along the application and robotics improved overall efficiency and handling,” Wowryk says.

Monitoring of the product and surrounding environment doesn’t end when it leaves the distribution center. “There are a number of temperature monitors used for recording temperature during transportation,” Wowryk says. “Most retailers request specific brands supported by their food safety program. All provide the key data required to identify any breaks in the cold chain.”

Neil Moran is a horticulturist and freelance writer and copywriter for the green industry.