Publishing their findings in the May 2004 issue of Food Chemistry, food scientists at the university of Lleida, also found an increase in oleic acid percentage in the fatty acid composition.
Oxidative rancidity development has been recognised as the leading cause of oil deterioration during storage. The two compositional factors of oils that determine their susceptibility to oxidation are the fatty acid composition and inherent antioxidant compounds. Virgin olive oil holds a rich source of natural antioxidants including carotenoids, tocopherols and phenolic compounds.
The researchers set out to investigate changes in the lipid substrate (fatty acid composition), and in the minor components - such as chlorophylls, carotenoids, alpha -tocopherol - and the phenolic fraction of commercial virgin olive oils of the Arbequina cultivar after 12 months of storage.
According to the scientists, there was evidence that the antioxidant fighting power of extra virgin olive oil could have a shelf life. The researchers say that they found a 30 per cent loss of chlorophyll content during storage. Carotenoid content followed a similar trend to that of chlorophylls.
Alpha-tocopherol levels fell by a massive 100 per cent after 12 months storage leading the scientists to suggest that alpha-tocopherol plays a signficant role as an antioxidant in the induction period of oxidation. Among the phenolic compounds, lignans were found to be the more stable.
In recent years extra virgin olive oil has been the central element for a host of studies on the mediterranean diet as researchers investigate why the dietary regime in the mediterranean basin ?olives, tomatoes, fish, olive oil ?appears to combat heart disease. According to the World Health Organisation (WHO), heart disease and strokes are the major causes of death and disability in ageing women, accounting for close to 60 per cent of all adult female deaths.
Full findings of the paper 'Changes in commercial virgin olive oil (cv Arbequina) during storage, with special emphasis on the phenolic fraction,?/i> by J. R. Morell? M. J. Motilva, M. J. Tovar and M. P. Romero are published in Food Chemistry (2004) 85:357-364.