Thermal extraction and characterization of pectin from semi-solid by-products of the olive oil industry.

Background: The valorization of agro-industrial by-products is crucial for promoting sustainability and circular economy. Olive mill semi-solid by-products (OMSbP), also known as alperujo, contain valuable bioactive compounds, including pectin, which can be extracted and used in food applications. However, the structural properties an antioxidant potential of these pectin require further characterization to assess their potential as functional ingredients.

Results: In the present study, pectin was extracted from OMSbP using a citric acid-based thermal extraction process. The yield varied depending on the olive variety and ripeness degree, with higher extraction efficiency in more mature samples (48.2 g kg^-1). Structural analysis by attenuated total reflectance/Fourier transform-infrared spectroscopy confirmed a high homogalacturonan content (~500 g kg^-1) and a degree of methyl esterification of approximately 60%. The monosaccharide profile indicated enrichment in arabinose, rhamnose, galactose and mannose. Antioxidant activity, assessed through DPPH (i.e. 2,2-diphenyl-1-picrylhydrazyl) radical scavenging, showed a strong correlation with mannose content (r = -0.9967). Additionally, pectin-based films demonstrated thermal stability comparable to commercial pectin used in food packaging.

Conclusion: This study highlights the potential of OMSbP-derived pectin as a biofunctional ingredient with antioxidant activity and thermal stability. The extraction method ensures a sustainable approach for utilizing olive industry by-products. Future research should explore its bioavailability and application in edible films and coatings. © 2025 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.