2002/12/19 by Sergio Gómez‐Alonso, Giuseppe Fregapane, María Desamparados Salvador +1 · 195 citations
Chemistry · Medicine · Agricultural and Biological Sciences · #Edible Oils Quality and Analysis #Phytochemicals and Antioxidant Activities #Essential Oils and Antimicrobial Activity #Hydroxytyrosol #Chemistry #Tyrosol #Antioxidant #Deep frying #Food science #Trolox #DPPH #Composition (language) #Fraction (chemistry) #Organic chemistry #Polyphenol #Chromatography
paper · doi:10.1021/jf025932w
published in Journal of Agricultural and Food Chemistry 51(3), 667-672 (American Chemical Society)
openalex publication_date 2002/12/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/22
The concentration of hydroxytyrosol (3,4-DHPEA) and its secoiridoid derivatives (3,4-DHPEA-EDA and 3,4-DHPEA-EA) in virgin olive oil decreased rapidly when the oil was repeatedly used for preparing french fries in deep-fat frying operations. At the end of the first frying process (10 min at 180 degrees C), the concentration of the dihydroxyphenol components was reduced to 50-60% of the original value, and after six frying operations only about 10% of the initial components remained. However, tyrosol (p-HPEA) and its derivatives (p-HPEA-EDA and p-HPEA-EA) in the oil were much more stable during 12 frying operations. The reduction in their original concentration was much smaller than that for hydroxytyrosol and its derivatives and showed a roughly linear relationship with the number of frying operations. The antioxidant activity of the phenolic extract measured using the DPPH test rapidly diminished during the first six frying processes, from a total antioxidant activity higher than 740 micromol of Trolox/kg down to less than 250 micromol/kg. On the other hand, the concentration of polar compounds, oxidized triacylglycerol monomers (oxTGs), dimeric TGs, and polymerized TGs rapidly increased from the sixth frying operation onward, when the antioxidant activity of the phenolic extract was very low, and as a consequence the oil was much more susceptible to oxidation. The loss of antioxidant activity in the phenolic fraction due to deep-fat frying was confirmed by the storage oil and oil-in-water emulsions containing added extracts from olive oil used for 12 frying operations.