Improving the fatty acid composition of 'Chemlali' virgin olive oil through clonal selection.

Sfax Province is one of the most important olive oil-producing regions in Tunisia, where plantations consist entirely of the cultivar 'Chemlali'. The fatty acid composition of 'Chemlali' olive oil is characterised by having relatively low levels of C-18:1. A selection programme to obtain 'Chemlali' olive clones with improved fatty acid compositions was initiated in 1994. Principal component analysis was applied to our chemical analysis data to reveal fatty acids present at the highest levels, in order to discriminate between the 36 clones studied. C-18:1, and C-18:2 fatty acids, and the mono-unsaturated:polyunsaturated fatty acids ratio were the most useful variables with which to classify the clones into four groups. One of these groups contained ten 'Chemlali' clones characterised by having high levels of C-18:1, and relatively low levels of C-16:1, and C-18:2 compared with the cultivar 'Chemlali'. We have extended this selection by including other discriminatory criteria such as stability against oxidation, and related anti-oxidant levels, to obtain six 'Chemlali' clones with improved chemical compositions for virgin olive oil production.