Determinants factors of antioxidant capacity and phenolic content of Lebanese olive oil

Abstract

Background: Olive Oil (00) is premium oil which plays an important part of the Mediterranean cuisine due to its nutritional and sensory characteristics. Studies highlight the nutritional benefits associated with the consumption of 00 including the low level of saturated fatty acids (SFA), the high level of monounsaturated fatty acids (MUFA) and the moderate level of polyunsaturated fatty acids (PUFA) along with minor constituents including phenolic compounds. Studies highlight the importance of phenolic compounds as they are the major bioactive of 00 which contribute to its sensory, organoleptic and biological properties, in addition to their antioxidant capacity and their ability to provide oil stability to oxidation thus increasing its shelf life. However, several agroindustrial factors are reported to affect the types and quantity of phenolic and antioxidant content of 00. Objectives: The purpose of this research is to identify the major agro-industrial factors that affect the antioxidant capacity and the phenolic content of Lebanese 00 and to study the correlation between the antioxidant capacity and the phenolic content of 00 Methods: 00 samples (n= 54) from 2016 crop, were originated from two areas: Zgharta-Koura (North) and Jezzine (South). These samples were collected in triplicate from 3 processing systems at 3 harvesting times by 3 different farmers at each harvesting. Liquid-Liquid extraction was used for the extraction of the phenolic compounds from 00 followed by Folin-Ciocalteu method for their quantification and 2,2-diphenyl-1-picrylhydrazyl (DPPH) for the determination of their antioxidant capacity. The data collected were analyzed and used to calculate the concentration of antioxidant and total phenolic content (TPC) of 00 samples. Moreover, the differences between means was assessed using Multivariate Analysis of Variances (MANOVA) and Three-way Analysis of Variance (ANOVA). The correlation between the antioxidant capacity and TPC was analyzed using the Spearman Correlation and Logistic Regression. The effect of 00 categories on TPC and antioxidant capacity was assessed using Independent samples /-test and Mann Whitney U-test. Results: Results indicated that the level of TPC of 00 samples ranged between 78.92 and 202.97 mg GAE.kg' of oil and the level of the antioxidant capacity ranged between 0.28 and 27.14%. Results also showed that the geographical origin, the harvesting time and the processing time had no significant effect on 00 TPC content and the antioxidant capacity. The results also reported a mid, positive correlation between TPC and the antioxidant capacity. In addition to the high significant difference between TPC averages of virgin olive oil (VO0) and extra virgin olive oil (EVOO). TPC level was shown to be higher for EVOO as compared with those from VOO.