Researchers at Oregon State University have discovered a material found in blueberry leaves can be used to coat the berries themselves, delivering longer shelf life, boosted antioxidants, and pathogen protection.
OSU food scientist Yanyun Zhao worked with a group of international researchers in China. The team discovered an edible coating crafted with an extract from blueberry leaves slowed berry decay.
Zhao said the naturally derived coating offers a number of advantages, including taking a usually discarded commodity and putting it to good use.
"Normally, blueberry leaves fall to the ground as waste," said Zhao, a food science and technology professor in OSU's College of Agricultural Sciences. “We've discovered a use that can change how the berries are stored, sold, as well as increasing their nutritional value.”
Additionally, the coating causes the berries to retain water longer. The capability provides two benefits: extending berry life, and higher fruit volume at the point of sale (which can mean greater profits for producers).
Berries with the coatings can be washed and packaged as ready-to-eat products. Typically, berries are sold at retail unwashed, because the rinsing process washes away the natural waxy coating which preserves the fruit.
Blueberry leaves (which sometimes are employed as an herbal remedy) contain high levels of antioxidant phenolics, chemical compounds with antimicrobial properties that protect against fungi and bacteria, such as E. coli and Salmonella.
Researchers generated the coatings by mixing the blueberry these phenolic extracts with chitosan, a preservative derived from crustacean shells. The researchers experimented by using leaves picked during different phases of berry maturity; additionally, they formulated the leaf extracts into five different coating treatments based on varying levels of phenols.
The scientists dipped the blueberries in the liquid coatings, then allowed them to dry at room temperature. Zhao added coating can be sprayed on the berries with a nozzle as they run by on a conveyor.
According to Zhao, the blueberry coating process likely will add to the cost of the fruit. However, she said, it is unclear exactly how much the process will bring the price up.
Other scientists on the project include Yun Deng, at Shanghai Jiao Tong University at the school's Bor Luh Food Safety Center.