During the production of olive oil, a considerable amount of olive leaves is produced as a “waste product”. However, these also have a variety of health-promoting properties and olive leaf extracts can, among other things, inhibit inflammation, protect the nervous system and prevent damage caused by free radicals.
A current study involving experts from the University of Porto determined the polyphenol content in olive leaves from different regions of Portugal and also determined which liquid extraction process is particularly effective. The results are published in the English-language trade journal “Foods”.
Olive leaves are not waste
Around two million tons of olive oil are produced annually in Europe alone, and the production of olive oil produces a significant amount of olive leaves, which are usually considered waste, the team reports.
However, since olive leaves are rich in phenolic compounds with health-promoting properties, experts say they should be evaluated as a potential functional food ingredient.
Healthy phenolic compounds
The phenolic compounds in olive leaves have antioxidant, anti-inflammatory, hypoglycemic, neuroprotective and antiproliferative properties, the researchers explain.
This shows that olive leaves are actually too healthy to be treated as waste and that sustainable methods for reusing olive leaf waste are required. The polyphenols contained in the leaves with their health-promoting properties should not simply be thrown away, but rather processed into food.
Extracts from the leaves are suitable for this, although experts have found that the solvent used for the extraction influences the content of certain healthy polyphenol compounds (hydroxytyrosol, oleuropein, verbascoside and luteolin).
In addition, it was shown that not only total polyphenols are important for antioxidant capacity, but also compounds that have slow-reacting antioxidant mechanisms and cause the formation of byproducts with antioxidant capacity, the team adds.
Further research should now be carried out to examine what options the extracted compounds from olive leaves offer for the development of functional foods. In addition, their potential for specific food processes such as emulsification and encapsulation should be further investigated, the researchers conclude. (as)