Addition of olive by-product extracts to sunflower oil: Study by 1H NMR on the antioxidant effect during potato deep-frying and further in vitro digestion

Potatoes were fried in sunflower oil enriched or not with Chetoui olive by-product extracts (leaves and olive mill wastewater), and afterwards submitted to in vitro gastrointestinal digestion. Frying oils and fried potato lipids before and after digestion were analyzed using proton Nuclear Magnetic Resonance (1H NMR) spectroscopy. Potential differences on lipid composition, oxidative status and after digestion also lipolysis degree, were studied. During deep-frying with oil replenishment, a higher generation of aldehydes was observed in non-enriched oils. During digestion, in the lipids of digested potatoes fried in non-enriched oil a higher degradation of linoleic chains and a higher generation of cis,trans-hydroperoxy- and cis,trans-hydroxy-octadecadienoates (primary oxidation compounds) and of alkanals was observed. A slightly higher lipolysis degree was reached in the lipids of potatoes fried in enriched oils. These findings suggest that the addition of both extracts could exert a potential antioxidant effect during frying and digestion, enhancing the quality, safety and nutritional value of fried food. •Olive by-product extracts reduced lipid oxidation during frying and digestion.•The higher the total phenolic content in extract, the higher its protective effect.•If enriched, the generation of aldehydes was reduced in oils during potato frying.•During frying in enriched oils, potatoes were also enriched in olive phenolics.•During digestion of potatoes fried in enriched oils, lower oxidation was observed.