• Deep frying;
  • enrichment;
  • french fries;
  • oleuropein;
  • olive leaves;
  • olive oil;
  • soybean oil;
  • sunflower oil


Olive oil, sunflower oil and soybean oil were enriched with an olive (Olea Europaea) leaf extract rich in oleuropein at a supplementation level of 100 mg total phenolics per kg oil. Supplemented oils were used for deep frying of potatoes for eight successive frying sessions without replenishment under domestic frying conditions. Supplemented oils contained oleuropein while deep frying resulted in a gradual decrease in oils oleuropein content. After the eighth successive frying, oleuropein was still detected in oils, its retention being 3.2–12.4%. Deep frying of potatoes in supplemented oils succeeded in preparing French fries containing oleuropein even after eight successive fryings. Contrary to the oil type, the number of frying sessions affected potatoes oleuropein content. Oleuropein intake by consuming French fries deep-fried in enriched oils was approximately ten times higher in potatoes prepared in the first frying session as compared to the respective intake after the eighth frying.