New Technology Prolongs Produce Freshness

Nutritionists encourage eating a healthy diet rich in fresh fruits and vegetables. In response, consumers flock to their grocery stores and stock up these healthful foods. Too often, though, produce spoils soon after purchase. This is becoming more common as more produce is imported from around the world.

The cause of the untimely spoilage is ethylene, a plant hormone that fruits and vegetables produce naturally as they ripen. Even at temperatures colder than 39° Fahrenheit, apples and avocados produce high quantities of ethylene. The situation is complicated when fruits and vegetables are packaged for long trips—as the air in the confined container circulates, the concentration of ethylene gas, even as low as .01 parts per million, accelerates the ripening of stored produce.

Postharvest losses due to spoilage, estimated at 30 to 40 percent worldwide, affect the economic success of growers, packers, storage houses, and distributors of produce.

With funding from USDA’s Cooperative State Research, Education, and Extension Service (CSREES), Dr. Reza Shekarriz and W. L. Allen of Fluid Analytics, Inc., in Lake Oswego, Ore., have developed a compact sensor to accurately measure low concentrations of ethylene on transport containers.

“This issue is becoming more critical as global trade and year-round consumption of fresh fruits and vegetables increases,” Shekarriz said. “Ethylene-related problems make up a significant portion of postharvest losses in developing countries, resulting in negative economic impacts worth billions of dollars every year.”

Produce freshness can be controlled by carefully monitoring and regulating exposure to ethylene during transport. Reducing produce exposure to ethylene slows the natural ripening process, thereby extending produce shelf life.

The new sensor continuously samples air at a regulated flow rate, normally 12 to 30 cubic inches of air per minute. Not only can the sensor detect ethylene at concentrations low enough to ripen produce, it also reports ethylene concentration in real-time to provide greater control over ethylene levels during transport.

“This sensor is far more sensitive to ethylene detection than previous technology. Future developments may increase sensitivity to provide better response times and will be integrated with ethylene scrubbers to actively remove ethylene from cold storage rooms and shipping containers” said Shekarriz.

This device is particularly important for organic produce that does not use other chemicals to control the ripening process.

The beneficiaries of this new sensing technology include horticulture and floriculture research institutions, growers, packing houses, cold-storage facilities, greenhouses, shipping containers, and consumers.

Scientists in the United States, Germany, England, France, and the Netherlands are already using prototypes of the ethylene sensor. Future work by this research team will focus on developing new technology to remove ethylene from an enclosed space to further reduce the complications of postharvest ripening.

This technology has been licensed to a French company, ABSOGER, for commercialization into the European cold storage market. The commercial units are expected to reach the market in mid-2009.