Determinants factors of quality indices, antioxidant capacity, phonolic content, and oxidatives stability of Lebanese olive

Abstract

Background -- Olive oil (OO) has been widely known as a main source of lipid in the Mediterranean diet. Over the years, the interest in virgin olive oil (VOO) consumption boosted due to its sensory properties characterized by its unique taste, flavor and color; and its health properties exerted by its monounsaturated fatty acids (MUFAs), tocopherols, and phenolic compounds. Phenols are minor compounds with antioxidant capacities that contribute positively to OO shelf life and stability to oxidation. Literature data have shown that several agro-industrial factors including harvesting time, processing system and geographical origin affect OO fatty acid composition, individual and total phenolic content (TPC), its antioxidant capacity (AC), its oxidative stability (OSI), and its quality indices. In Lebanon, few studies were conducted on olive cultivars, and due to the lack of homogenous agro-industrial conditions and appropriate sample size, little is known on Lebanese olive cultivars characteristics including TPC, AC and OSI, and on the suitable agro-industrial factors that could lead to the production of good quality OO. Objectives – The aim of the present work is to assess the effect of some agro-industrial factors on OO TPC, AC, and OSI, and to determine the correlation between the latter characteristics. This study also aims to assess the correlation between quality indices, and their impact on TPC, AC and OSI, and to determine practices that could lead to high quality OO. Methods – This cross-sectional study forms part of a project funded by the CNRS and implemented at LARI in collaboration with NDU, USJ and USAID/LIVCD project. Sampling was carried out on 108 VOO and extra virgin olive oil (EVOO) samples harvested from Lebanese northern (Akkar and Zgharta-Koura) and southern (Hasbaya and Jezzine) regions. Samples were collected at three harvesting times (early, intermediate, late) and crushed using different types of mills (traditional, sinolea, two-phase and three-phase decanters). Three samples were processed at each harvesting time and for each processing system. Peroxide value, free acidity, K232, and K270 were determined on the same samples in previous studies according to IOC methods of analysis (EEC reg 2568_91). High performance liquid chromatography (HPLC) was used to identify individual phenolic compounds, and gas chromatography to determine OO fatty acid composition. Also, OSI was determined using Rancimat instrument (El Riachy et al. 2017). During the present study, Folin-Ciocalteu assay was conducted to quantify total phenols content (TPC) after their extraction using liquid-liquid extraction technique (by methanol/water 60/40, v/v), and AC was identified using 2,2-diphenyl- 1 –picrylhydrazyl (DPPH) free radical scavenging method. Results – Peroxide value and UV absorbance were within the limits set by EU Commission Regulation 1989; however, FA exceeded those limits. Samples mean TPC was 157.0 ± 32.8 mg.kg', mean DPPH was 12.1 ± 4.6%, and mean OSI was 8.2 ± 1.6 h. The obtained results show that early harvested OO samples obtained from Akkar using 3 phase decanters exhibited the highest TPC. Also, early harvested samples from Jezzine using 3-phase decanters showed the highest AC. As for resistance to oxidation, early harvested samples from Hasbaya using 3-phase decanters possessed the highest OSI. Furthermore, the obtained results also revealed a moderate positive correlation between TPC and AC, and a strong positive one between TPC and OSI. However, weak negative correlations were observed between OO TPC/AC/OSI and its quality indices, and weak to moderate ones between individual phenols and the latter parameters. Conclusion – Agro-industrial factors contribute to OO's quality indices and characteristics including individual and total phenolic content, antioxidant capacity, and thereby resistance to oxidation. It also determines the characteristics, composition, and nutritional properties of Lebanese OO samples, obtained from different areas, and undergoing various pedoclimatic, industrial and agricultural conditions.