Assessment of chemical quality properties and phenolic content of different samples of Algerian olive oil

Abstract

The consumer necessity for a good quality of olive oil in terms of its lipid and phenolic profiles is demanded to preserve a good health and to combat illnesses. The conformity of olive oil with the International Olive Council standards requires the determination of certain chemical parameters including free acidity, saponification and peroxide indices. Our study was based on a comparative evaluation of chemical quality indices and extraction of phenolic compounds from different samples of olive oil of different durations of storage, from different regions of Algeria and with different preparations. The most recent olive oil sample presented the least acidity (1.88%) and saponification index (185.32 mg of KOH/g of oil). However, the sample conserved for five years revealed the highest quantities of total phenolics (0.56 ± 0.02 mg GAE/g oil) and flavonoids (0.174 ± 0.019 mg CE/g oil). Different results were collected comparing samples of olive oil from different regions from Algeria. Acidity percentages were ranged from 0.7 to 3.1%, peroxide index from 8 to 53meqO₂/Kg of oil and saponification number from 166.61 to 201.11 mg KOH/g of oil. Yields of phenolic extraction results revealed percentages from 0.11 to 0.24%. The traditionally prepared olive oil presented the best quality with an acidity of 1.01% and a saponification number of 187.10 ± 13.68 mg KOH/g oil. Whereas, the industrially prepared one exhibited the lower number of peroxide with 8.30 ± 2.88 meqO₂/ kg oil. The quality of olive oil was influenced by time, geographical region and mode of extraction. Conserved olive oils may be destined for the manufacture of soaps or the extraction of phenolic compounds