engleski

Influence of malaxation time on phenols and volatile compounds of virgin olive oil obtained from phenol enriched olive paste (Buža cv.)

The malaxation of olive paste is an essential olive oil production step which allows not only satisfactory yields of oil extraction. During malaxation, changes of oil composition also occur because of the partition phenomena among oil, water and solid phase and the activity of fruit enzymes released during crushing. Quality and quantity of extracted oil can be influenced by varying the conditions of this operation (such as time, temperature, addition of technological coadjuvants). Different malaxation times (30, 45 and 60 min) were applied to olive paste of Buža cultivar which was previously enriched with the phenolic extract obtained from the freeze-dried olive pulp of Istarska Bjelica cultivar. Olive paste was phenol enriched at the level of 38% (w/w) in order to improve the phenolic content in resulting oils and to check the influence on volatile compounds. Phenols in olive pastes and corresponding olive oils were determined by RP HPLC with UV-DAD detection, whereas volatile compounds in oils were analyzed by SPME-GC-MS. An addition of phenolic extract to olive paste mostly affected the amounts of dialdehydic form of oleuropein aglycone and apigenin which increased by 473% and 90% in Buža paste, respectively. The major phenolic compound in olive paste was dialdehydic form of decarboxymethyloleuropein aglycone, as well as in the oil. By increasing the malaxation time, the decrease of free hydroxytirosol, tyrosol and verbascoside in enriched olive paste was observed. The similar was observed for oil samples, except for vanillin which increased (by 31%) along with the malaxation time. Among volatile compounds responsible for positive odour notes, the prolonged malaxation time had a significant negative effect (Tukey’s test, p<0.05) on hexanal, hexan-1-ol and Z-3-hexenyl acetate. Longer malaxation time (60 min) of olive paste enriched with the phenolic extract showed more pronounced effect on phenols than on volatile compounds.

Buža cultivar; malaxation time; olive oil; phenols; volatiles

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