engleski

Phenols in Olive Paste as Modulators of Volatiles from LOX Pathway in Virgin Olive Oils from Buža Cultivar

Biochemical synthesis of virgin olive oil volatile substances during olive processing depends on activity of endogenous enzymes involved in the LOX pathway. Phenols present in olive paste could be one of the inhibitory factors, since it is known that phenolic compounds are able to bind and inhibit various enzymes. Olive paste of Buža cultivar, known to have low phenols content and a relatively high C6 volatiles mass ratio in oil, was fortified with phenolic extract from olive fruits during processing, in order to study the effect on volatile compounds in oil. Oil samples were obtained by a laboratory plant from olive pastes containing two levels of phenols content (real and increased by 20%). Phenols in oils were determined by RP HPLC with UV-DAD detection using tyrosol, apigenin and luteolin (calibration standards) and syringic acid (internal standard). Volatiles were analysed by SPME-GC-MS with 4-methyl-2-pentanol as an internal standard. The increase of total phenols mass ratio in olive paste by 20% has led to a much higher rise of phenols in oil samples (hydroxytyrosol 185% ; oleuropein and ligstroside derivatives by 175% and 750%, respectively). Oils from fortified pastes had up to 10 times reduced values of Z-3-hexenal and 2 times of E-2-hexenal, E-2-hexen-1-ol and hexyl acetate. Other substances (hexanal, E-3-hexen-1-ol, Z-3-hexenyl acetate and C5 compounds) showed minor changes in relation to the increased phenols mass ratio in olive paste. A relatively low odour threshold value of Z-3-hexenal, E-2-hexenal and E-2-hexen-1-ol suggests that a radical decrease of their mass fraction in oil should have an evident negative impact on the perception of green odour notes. Results confirm the hypothesis of inhibitory effect of phenols compounds in olive paste on the biosynthesis of the most important volatile compounds of pleasant virgin olive oil aroma.

olive oil; olive paste; phenols; volatiles; Buža

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