Comparative investigation of minerals, chlorophylls contents, fatty acid composition and thermal profiles of olive leaves (Olea europeae L.) as by-product

This work presents a chemical (the minerals, chlorophyll contents and fatty acids) and thermophysical investigation (DSC profile) of four varieties of olive leaves grown in Tunisia. The total chlorophyll contents of olive leaves ranged from 1132.33 to 1795.93 ppm. The results showed that linolenic acid (C-18:3) is the major fatty acid in olive leaves (from 30.02 to 42.16%), followed by oleic acid (C-18:1) and palmitic acid (C-16:0). The thermal profiles of olive leaf extracts determined by their DSC melting curves revealed simple thermograms with a single peak after melting. The hexane extract of the Chemchali variety, which contained relatively high unsaturated fatty acids and low saturated fatty acid levels, exhibited the lowest peak temperature value (54.59 degrees C) and required the smallest amount of energy for melting (31.57 J.g(-1)). This study showed that olive leaves possessed physicochemical properties and a fatty acid composition that may become interesting for industrial applications.