Olive mill wastewater as a functional resource of bioactive compounds for Agro-Food Industries

By Paola Foti and Cinzia Caggia

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Olive oil production is a vital agro-industrial activity for the countries of Mediterranean basin, howewer it is associated with the generation of large amount of by-products. Therefore the recovery and the valorisation of olive oil by-products represents one of the priorities for any implementation of circular economy strategy. In particular, in many countries, the olive mill waste water (OMWW) still constitutes a significant quantity of the olive oil extraction process and a relevant environmental issue for oil mills. Worldwide, the production of OMWW is estimated at 6 × 106 m3, with the largest production in Mediterranean countries. Olive oil by- products contain high concentration of bioactive compounds; which were concentrated in the aqueous phase during olive extraxtion (Fig 1). Therefore OMWW are rich in phenols, with a content of hydroxytyrosol even higher than in oil [1], tyrosol, oleuropein, flavonoids and other compounds, such as molecules with high interest in pharmaceutical and nutraceutical fields [2]. The beneficial effect of olive oil polyphenols has been recognised by the European Food Safety Authority with the statement: ‘Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress’.

Nowadays for OMWW uses are proposed in agriculture, in bio-energies production, and recently in pharmaceutical, cosmetic, biochemical and food industries where a considerable market value to the by-product itself is conferred. In particular, the application in food industries is of increasing interest, since appropriate additions can increase the functional value and also extend the shelf-life of final products, making a by-product a natural preservative or additive with bioactive activity. Futermore OMWW are added as such or as extracts, concentrated and stabilised and, in some cases, microencapsulated. In several studies, OMWW have been exploit as ingredients in formulation of new foods in meat, dairy-products and cereals [3].

The aim of the PhD project is the valorisation of the OMWW through fermentation using selected microbial pools of yeasts and lactic acid bacteria, in single and mixed cultures, in order to debitter, stabilise and increase the nutritional value of the final products (Fig.2). The biotechnological application of microorganisms could be seen as a way to valorise OMWW with the aim of obtaining high added value compounds [4]. The benefits attributed to food fermentation are numerous and include energy savings during matrix processing, desired biochemical changes for nutritional improvement, safety, shelf life and improved sensory properties [5].

On the left Prof. Cinzia Caggia, Full Professor of Agricultural Microbiology (Superviosor of Phd) and on the right Paola Foti, Phd student in Biotechnology

I graduated in Food Science And Technology at University of Catania. Right after I carried out research activities, as a research fellow, at the Research Centre for Olive, Fruit and Citrus Crops (CREA-OFA), Acireale (CT) focusing on the reuse and valorisation of citrus pulp, as a source of pectin with prebiotic activity. The prebiotic and multifunctional activities of pectin-derived oligosaccharides (POS) are very promising and the results obtained showed that POS could be used as emerging prebiotics with enhanced properties due to their antioxidant, antimicrobial and anti-tumour activities and their ability to modulate the microbiota. I am currently a PhD student in Biotechnology at the University of Catania. The aim my PhD project is the valorisation of the by-products of virgin olive oil production through different microbial pools. The olive mill wastewater so treated will be proposed as a novel functional food with high polyphenols content. Omics approach will be applied in order to monitor the fermentation kinetics of olive mill wastewater. In addition, the project aims at the set up of a new “olive creamy paté” for human consumption, through a micro-fermentation process combining microbial pools of yeast strains and lactic acid bacteria able to debitter, stabilize and increase the nutritional value of a product with a high concentration of nutraceutical molecules.

References

1. Fernández-Bolaños, J.; Rodríguez, G.; Rodríguez, R.; Guillén, R.; Jiménez, A. (2006). Extraction of interesting organic compounds from olive oil waste. Grasas Aceites, 57, 95–106.
2. Romeo, F. V., Granuzzo, G., Foti, P., Ballistreri, G., Caggia, C., & Rapisarda, P. (2021). Microbial Application to Improve Olive Mill Wastewater Phenolic Extracts. Molecules, 26 (7), 1944.
3. Foti P., Romeo F.V., Russo N., Pino A., Vaccalluzzo A., Caggia C., Randazzo C. L. (2021). Olive mill wastewater as renewable raw materials to generate high added-value products for agro-food industries. Applied Sciences. 11, 7511.
4. Ahmed, P.; Fernández, P.M.; Figueroa, L.I.C.; Pajot, H (2019). Exploitation alternatives of olive mill wastewater: Production of value-added compounds useful for industry and agriculture. Biofuel Res. J., 6, 980–994.
5. Ashaolu, T. J. (2020). Safety and quality of bacterially fermented functional foods and beverages: A mini-review. Food Quality and Safety, 4 (3), 123-127.