An orange, to most people, is simply a piece of fruit. But to food scientist Yang Shan, it is much more. The discarded pith, pips, skin and membranes of citrus fruits are untapped reservoirs of useful compounds.
“Our goal is to make full use of the citrus fruit,” says Shan, head of the academic committee of the Hunan Academy of Agricultural Sciences in Changsha, China. “Due to the lack of key technologies and equipment, use of citrus byproducts is low. Our aim is to comprehensively utilize the useful substances in citrus waste in a closed-loop process.”
Reducing the 30% of citrus fruit by weight that is discarded during processing would reduce the environmental impact of fruit farming, says Shan. His team is using waste from citrus fruits to create a wide range of products.
NANOPARTICLES
Much pectin from citrus peels and membranes goes to waste, says Shan. His team has developed a potential use for pectin that might otherwise be discarded, producing copper nanoparticles with antimicrobial properties.
Copper nanoparticles have unusual properties, including the ability to halt the growth of bacteria and fungi. That property could have uses in water purification or in coatings for medical devices to prevent infections.
Nanoparticles are difficult to produce. Shan’s team has developed an efficient and environmentally friendly method for synthesizing copper nanoparticles using pectin as the stabilizer, and ascorbic acid, which can also be extracted from citrus, as the reducing agent. In lab tests, the citrus-derived nanoparticles inhibit growth of bacterial cultures of Escherichia coli, Staphylococcus aureus and Aspergillus japonicus.
In another study, the team synthesized silver nanoparticles from silver nitrate, using hesperidin and pectin as the reducing agent and stabilizer. Incorporating hesperidin and pectin into the silver nanoparticles synergistically enhanced their antibacterial properties.
ESSENTIAL OIL
Shan’s team has also delved into the mechanism of action of one promising antimicrobial, essential oil extracted from citrus fruit, such as oranges and fingered citron (a variety of Citrus medica). The team tested it against the foodborne pathogenlisteria. Listeria monocytogenes can survive environments with high-salinity, low temperature, low pH and low moisture, posing a challenge for safe food processing. However, Shan and his coworkers discovered that citrus essential oil has antibacterial activity against L. monocytogenes.
NEOHESPERIDIN
Shan’s team also is exploring neohesperidin, an antioxidant flavonoid molecule extracted from bitter orange (Citrus aurantium). Blood glucose levels fell, and abnormal lipid metabolism stabilized in rats on a high-fat diet that were fed neohesperidin dihydrochalcone for 12 weeks. Shan’s team believes neohesperidin extracted from citrus fruit might have the potential to help treat diabetes or problems with high blood lipids in humans.
Source: Nature Portfolio
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