Development and characterization of functional ingredients from olive pomace
: bioactivity and potenttial aplication

  • Tânia Isabel Bragança Ribeiro (Student)

Student thesis: Doctoral Thesis


Currently, a large amount of the total European food supply chain waste (between 19 and 39%) isproduced during food processing. The olive oil industry is no exception, generating large quantitiesof by-products and wastes annually with high phytotoxic impact, but also rich in several bioactivecompounds and nutrients with potential application as food ingredients. Thus, it is imperative toimplement strategies to reduce waste and valorise by-products to improve the food industry'seconomic and environmental sustainability. Olive pomace is the most prominent by-product of themodern olive oil industry, and its proper valorisation is one of the major obstacles to olive oil industryachieve a sustainable production chain aligned with the principles of the Circular Bioeconomyconcept. This project aimed at achieving a “zero waste” valorising approach to olive pomace thatprioritised the high over low added-value products, through the production and characterisation offood ingredients, namely high-value powdered ingredients rich in several bioactive compounds,followed by the validation of their biological activities related with health benefits as prevention andreduction of the prevalence of cardiovascular diseases, diabetes and gut disorders and, theirapplication in the development of functional foods.A “zero waste” strategy was achieved for olive pomace. This strategy is based on a feasible fractionapproach, and it was obtained a liquid fraction that revealed a high amount of hydroxytyrosol (513.61-625.76 mg/100 g dry weight) and pulp fraction that was characterised to be a good source ofantioxidant dietary fibre. Additionally, it was achieved a stones fraction that exhibited substantialhigher heating values (18.65-18.94 MJ/kg). These results supported the potential value-added of theliquid and pulp fractions from olive pomace as functional food ingredients and as biofuel to stones.After validating the liquid and pulp fraction potential as food ingredients, new two stable and safe,powdered ingredients without any extraction step were developed, namely a liquid-enriched powder(LOPP) and a pulp-enriched powder (POPP). LOPP exhibited a significant amount of mannitol (141g/kg), potassium (54 g/kg) and hydroxytyrosol/derivatives (5 mg/g). POPP exhibited a high amountof dietary fibre (620 g/kg) associated with a significant amount of bound phenolics (7.41 mg gallicacid equivalents/g fibre dry weight) with substantial antioxidant activity. POPP also revealed anunsaturated fatty acid composition similar to that of olive oil (76% of total fatty acids) and areasonable source of protein (12%). Their functional properties (solubility, water‐holding and oil‐holding capacity), antioxidant capacity and antimicrobial activity were also assessed, and theirbiological safety was validated. The multifunctionality and applicability as nutritional enhancers,health-benefits promoters and preservatives of the olive pomace powders were recognised.The in vitro simulated digestion allowed concluding that phenolics and minerals from LOPP werenegatively affected by digestion. However, a significant bioaccessibility of potassium andhydroxytyrosol was verified ( 57%) and its bioactivities were only moderately affected. Regardingits bioactivities, at least half of the antioxidant activity (measured by Oxygen Radical AbsorbanceCapacity assay), -glucosidase inhibition activity and angiotensin-converting enzyme inhibitoryactivity (91.98%) were retained and bioaccessible after in vitro digestion. In its turn, POPP digestion Abstractxiirevealed a significant loss of phenolics in the oral step (62.48%), but the dietary fibre role asphenolics’ carrier allowed recovering a significant amount of phenolics in the stomach (77.11%) anda bioaccessibility index of at least 50% (mainly for tyrosol and its glucoside). POPP dietary fibre alsopositively interacts with lipids decreasing the saturated fatty acids bioaccessibility (5-6%) andfacilitating the unsaturated fatty acid bioaccessibility (4-11%).After the in vitro digestion system of both olive pomace powders, the colon-available fractions LOPPand POPP exhibited an abundant composition in phenolics, but also dietary fibre with potential guthealth benefits as antioxidants, antimicrobial and prebiotic agents. So, the gut's potential beneficialeffects were analysed by in vitro faecal fermentation of the undigested fractions retained in the colonafter in vitro simulated gastrointestinal digestion. The 16S rRNA gene analysis results showed thatLOPP and POPP did not negatively impact gut microbiota diversity. The short-chain fatty acidsanalysis showed a higher production of these fatty acids (acetate > butyrate > propionate) by LOPPand POPP than by fructooligosaccharides. The identification of phenolic metabolites by LC-ESIUHR-QqTOF-MS followed by supervised cluster and hierarchical clustering analysis allowed toevaluate the metabolite patterns of olive pomace powders phenolics throughout faecal fermentation,explaining the potential biological activities exhibited in the gut by these powders. Both powdersshowed significant total phenolic content and oxygen radical absorbance capacity during faecalfermentation. But also, mucin‐adhesion inhibition ability against pathogens as Bacillus cereus(22.03%) and Listeria monocytogenes (20.01%), specially POPP.Finally, to validate olive pomace powders' performance as functional ingredients, LOPP and POPPwere incorporated into yoghurt to increase its content in dietary fibre, hydroxytyrosol, andunsaturated fatty acids. POPP (2%) and LOPP (1%) addition to yoghurt allowed fulfilling the conditionon being a “source of fibre” and provides 5 mg of hydroxytyrosol and derivatives in a standard yoghurt(120 g), respectively. The addition of olive oil, together with olive pomace powders, was alsoinvestigated in order to understand the lipids-phenolics interaction, and not only POPP additionimproved the yoghurts’ unsaturated fatty acids profile, but the olive oil addition together both olivepomace powders also improved too. Besides that, all yoghurts fortified with olive pomace powdersexhibited higher total phenolic content and antioxidant activity. The in vitro digestion of yoghurtsshowed that olive oil incorporation together with olive pomace powders increased the bioaccessibilityof hydroxytyrosol (LOPP + olive oil) and hydroxytyrosol glucoside (POPP + olive oil). Despite thereduction of antioxidant activity after digestion, the yoghurts formulations with olive pomace powderscould be considered suitable carriers to deliver hydroxytyrosol, unsaturated fatty acids and fibre tothe consumers.In short, the results from this work will contribute to the sustainability of the olive oil industry in circularbioeconomy context, through the development of value-added ingredients to the food industry witha positive impact in health, offering also a solid biofuel.
Date of Award13 Apr 2021
Original languageEnglish
Awarding Institution
  • Universidade Católica Portuguesa
SupervisorMaria Manuela Pintado (Supervisor), António Vicente (Co-Supervisor) & João Nunes (Co-Supervisor)


  • Olive pomace
  • Powder ingredients
  • Bioaccessibility
  • Health benefits


  • Doutoramento em Biotecnologia

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