Biochemical aspects of olive freezing-damage: Impact on the phenolic and volatile profiles of virgin olive oil

- Freezing-damage irreversibly alters phenolic and volatile metabolism in olive fruit.
- Freezing-damage reduces flavor biosynthesis during virgin olive oil extraction.
- Oils from freeze-damaged olives have low contents of secoiridoid compounds.
- Oils from freeze-damaged olives have low levels of C6 volatile compounds.

In this study, the biochemical changes induced by severe freezing of olives of the Picual and Arbequina cultivars were evaluated, paying particular attention to the phenolic and volatile profiles of the oils obtained from them. The content of the main phenolic glycosides, oleuropein and demethyloleuropein, and the activity levels of β-glucosidase and polyphenol oxidase in the olive tissue were severely reduced by freezing. On the contrary, unusually high levels of hydrolytic secoiridoid derivatives were found in freeze-damaged fruits. In both cultivars, the oils obtained from freeze-damaged fruits contained significantly lower levels of secoiridoid compounds, with a 21% and 42% decrease in Picual and Arbequina, respectively. The volatile composition of the oils obtained from Arbequina freeze-damaged fruits were also more strongly affected than that of Picual oils, with a higher reduction in the content of C6-aldehydes, 85% and 65% respectively. The changes observed in the main volatile components were closely related to the changes provoked by freezing in the activity level of the enzymes of the lipoxygenase pathway.