Many people throw away citrus peels because they are too bitter to eat raw, but this outer layer of the fruit’s skin is a rich source of many sought-after beneficial compounds. The peel is in demand for companies seeking to use those compounds for health and pharmaceutical products.
Christina Dorado, lead scientist and chemist at the U.S. Department of Agriculture (USDA) U.S. Horticultural Research Laboratory’s Citrus and Other Subtropical Products Research Unit in Florida said citrus peels are good sources of antioxidants and anti-inflammatory compounds.
“It’s important to develop varieties and hybrids that are viable for commercial production,” Dorado said. “For citrus farmers, it is not just about growing fruits for food or juicing. The citrus peels are valuable too.”
Dorado noted that USDA’s Agricultural Research Service (ARS) for years has been developing citrus varieties and hybrids that show tolerance to HLB, also known as citrus greening. In a recent study, Dorado and the U.S. Horticultural Research Laboratory researchers assessed 22 different citrus varieties and new unique hybrids for the presence of anti-oxidants and anti-inflammatory compounds — also known as their phenolic profile — in the fruit peel. Each citrus variety and hybrid has a phenolic profile that has the potential to be utilized for precision nutrition and health supplement applications.
Key research findings included the following:
- The mandarin varieties had high levels of beneficial flavonoids called polymethoxylated flavones (PMFs), especially nobiletin and tangeretin.
- The mandarin/pummelo hybrids contained both PMFs and coumarins, which are largely absent in citrus and have shown potentially beneficial biological actions.
- The two trifoliate oranges, Flying Dragon and Gotha Road, showed big differences in their phenolic profiles. Gotha Road had more coumarins, while Flying Dragon had more psoralens, compounds that are structurally related to coumarins.
- Hybrids of mandarins with trifoliate orange parents often combined unique compounds from both species, creating new chemical profiles not found in traditional citrus varieties.
While the fruits tested in the study are not available for commercial production yet, the research shows promise that these fruits can be valuable for citrus growers.
“We found that these hybrids and varieties have a lot of beneficial compounds that are not found in traditional citrus fruits like oranges, limes, lemons and grapefruits, and so have not been studied as much or at all,” said Dorado.
According to Dorado, more research is underway to study the health effects of the compound mixtures of these fruits.
Source: USDA ARS
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