The chemical characterisation of locally grown olive leaf, fruit, and oil from Maltese and international varieties

Abstract

This dissertation is aimed at obtaining chemical characterization of olive leaf, fruit and oil from locally grown Maltese and International varieties. Thirteen olive varieties of both oil and dual purpose were selected, two of which were of Maltese origin; Tal-Bidni and Tal-Malti. Seven different olive oils were extracted from eleven of the selected varieties, five were blended and two were mono-varietal. The maturity index at harvest and olive oil yield were recorded. Chemical analysis was carried out on all samples of olive leaf, fruit and oil, for polyphenols using the Folin-Ciocalteau reagent, and for chlorophyll, anthocyanins, tint, colour intensity, and tonality using spectrophotometry. Olive oil samples were further analyzed for individual fatty acid content using GC-MS, and for total free fatty acids by titration. UV-spectra were obtained for all samples. The findings from the olive oil analysis revealed that the local Tal-Bidni variety was distinguishable from the rest in terms of fatty acids and polyphenolic content. Principal component analysis (PCA) conducted on the oil samples revealed that polyunsaturated fatty acids were inversely related to monounsaturated fatty acids, and that the maturity index and polyphenolic content showed a positive correlation. The findings from the olive leaf and fruit analysis indicated that the polyphenolic content had a similar trend in both fruit and leaf, and anthocyanin and chlorophyll content had different trends. PCA conducted on the olive leaf and fruit samples revealed that tint and tonality showed an inverse correlation with anthocyanin and polyphenolic content, and that chlorophyll content of leaves showed an inverse relationship with that of the fruit. Agglomerative hierarchical clustering (AHC) analysis revealed that the local variety Tal-Bidni is closely related to Bosana, Pendolino and Leccino, whilst the other local variety Tal-Malti is closely related to Frantoio and Ottobratica.