Posted: Thursday, May 26, 2011 9:00 AM
Courtesy of Michigan State University
Biodegradable and compostable plastic cartons are being tested by Michigan State University researchers to prolong the shelf life of sweet cherries.
Researchers say development could improve demand, sales
By DAN WHEAT
A team of research scientists is testing biodegradable and microperforated plastic packaging as a way to prolong the shelf life of sweet cherries.
The Michigan State University team, headed by Eva Almenar, who has her doctorate in food science and technology from the University of Valencia, Spain, may have a product available for commercial use in 2012.
The work is part of a four-year, $3.9 million federally funded program to improve production and marketing of sweet cherries. It is in its second year.
The program involves researchers at Michigan State University, Washington State University, Oregon State University, the University of California and Picker Technologies of Bellevue, Wash.
The Michigan team is testing a plastic made of polylactic acid, which is biodegradable, compostable, made from renewable resources and has been approved by the FDA for contact with food.
"Just because something is recyclable doesn't mean it is recycled, so in this case it's biodegradable even if it ends up in a landfill," said Matthew Whiting, program lead and stone fruit physiologist at WSU Irrigated Agriculture Research and Extension Center in Prosser, Wash.
Extending the availability of quality cherries should build consumer demand and increase sales, he said.
With microperforations of the material, oxygen depletion and growth of carbon dioxide is slowed, reducing respiration and microbial growth in the cherries to extend their shelf life, according to Almenar. In addition, the proposed package reduces water loss as it acts as a physical barrier.
When cherries are on the tree their loss of water, minerals and nutrients through respiration and transpiration are replaced by the tree. After harvest those losses are not replaced and weight loss, fungal growth and deterioration starts. Altering the gas mixture surrounding the cherries to a composition different from air prolongs quality for distribution and marketing, Almenar said.
The Michigan team has been testing a couple alternatives in polylactic acid packaging which have reduced cherry weight loss by about 10 percent after three weeks of storage. Testing will continue this season, Almenar said.
The team is studying whether polylactic acid can extend shelf life from the normal two weeks after picking to four to five weeks or more, she said. It depends on storage temperatures, she said.
Almenar does not know yet if the packaging will be more expensive.
Another part of the program is the development of stemless cherries to allow for mechanical harvesting.
The biocartons will benefit stem and stemless cherries, Whiting said.
The stem doesn't draw resources from the fruit once it's picked but there's some indication that stemless cherries last longer in storage, Whiting said. That is because they're not dented from stems, he said. Cherries with stems that jostle against each other in bag or containers develop "pitting" or denting in skin from stems, he said.
Sales of stemless cherries in premium packaging, like heat-sealed clamshells, will be tested this season in upper-end markets, Whiting said.