The study, funded by Spain’s Ministry of Science, sought to characterize the phenolic content of the by-products, extract the main phenolic compounds using industrial processes, and evaluate the antioxidant capacity of the resulting extracts.
“These effluents are ideal sources for obtaining antioxidant phenolic extracts for use in the food, cosmetics and nutraceutical industries, thereby improving the formulation of new functional foods and enabling the replacement of synthetic antioxidants,” the researchers wrote in the journal Foods.
Spain explores new uses for olive by-products
Accounting for 45% of the global production of olive oil and as the second largest producer of table olives, Spain generates large quantities of by-products such as alperujo (a mix of olive pulp, skin, stone fragments and vegetation water) and brine.
“The olive industry is experiencing significant growth, which is only held back by the environmental and management issues that its by-products can cause,” the researchers noted. “The two most polluting effluents produced are a new aqueous phase, or ‘alpechín ’, obtained from alperujo, which is the most important waste generated in the olive oil industry, and brine in the table olive industry.”
The high organic and phytotoxic loads of both by-products and the conductivity of the brines make their reuse difficult and pose a real technological challenge owing to the environmental problems they cause, the researchers explained.
These by-products also contain valuable bioactive compounds, particularly hydroxytyrosol (HT), tyrosol (Ty) and DHPG, that exhibit antioxidant activity and have shown promise as anti-inflammatory ingredients for cardiovascular, skin health and healthy aging product applications.
A new source of natural antioxidants
The researchers investigated three olive industry by-products: table olive brine, alperujo, and the new liquid alpechin fraction.
They extracted phenolic compounds from the liquid by-products using ion-exchange chromatographic columns—which act like a filter that traps the useful phenolic compounds while allowing other substances to pass through—and analyzed the resulting extracts and treated effluents to determine their phenolic composition and potential for further use.
The researchers measured the phenolic compounds, sugars, pH and conductivity in the olive by-products. They then used multiple tests to determine how strong the antioxidant properties of the olive by-product extracts were.
The chromatographic system successfully removed phenolic compounds from both alpechin and brine while producing concentrated phenolic extracts.
In alpechin, the treatment reduced total phenolics by about 64%, making this olive-industry waste less environmentally problematic, while the main compounds—HT, DHPG and Ty—decreased by 82%, 63% and 70%, respectively.
The treatment also reduced phenolic compounds in brine. Two passes through the chromatographic column removed approximately 60% of the total phenolics, with HT and Ty decreasing by 88% and 84%, respectively.
The alpechin extract showed stronger antioxidant activity than the brine extract, despite the brine extract containing more total phenolics. This result suggests that specific compounds, particularly HT and DHPG, contributed strongly to antioxidant activity, the researchers noted.
“The antioxidant activity data indicate that the extracts obtained have high potential, with HT being the main component,” the researchers wrote. “Compared with other extracts of the same nature, including olive oil by-products and table olives, twice the scavenging activity was observed for the three free radicals studied, and twice the reducing power of these extracts.”
Overall, the chromatographic process reduced the harmful phenolic content of the waste liquids and recovered valuable phenolic extracts with strong antioxidant properties.
“This demonstrates that the use of industrial technologies enables the production of extracts with high antioxidant activity for use in the food, cosmetics and nutraceutical industries, among others, which will add value to the system by not only allowing for the detoxification of by-products but also providing an additional benefit to the value chain,” the researchers concluded.
Source: Foods; doi: https://doi.org/10.3390/foods15193370; “Extraction of Antioxidant Phenolic Extracts from the Two Main Liquid Effluents of the Olive Industry.” Authors: Fernández Prior, et al.
