New six pack of olive oil research – Part 11
admin | June 12, 2011Olive oils were made from pitted and depitted olives and were malaxed under nitrogen and air. Total polyphenols, oxidative stability and antioxidant activity only increased when depitted olives were malaxed under nitrogen. Nitrogen atmosphere by itself had little effect on these parameters. Nitrogen did increase tocopherol (Vitamin E) content but also decreased chlorophyll content in the oils.
Yorulmaz et al. (2011) Improving olive oil quality with double protection: Destoning and malaxation in nitrogen atmosphere. European Journal of Lipid Science and Technology, 113, 637-643.
Over 1/3 of 25 Argentinean olive oils labelled extra virgin sampled from local supermarkets had campesterol levels higher than IOC limits. But as all other aspects of their chemistry were within specification, this suggests natural variation. However, 13 of the sampled oils simultaneously showed high levels of wax, (ECN42 R -ECN42 T) and 3.5 stigmastadienes which strongly suggests adulteration with seed or olive pomace oils. The authors state in their conclusion that “doubtful practices must be eliminated”.
Pardo et al. (2011) Purity, quality and stability of Argentinean virgin olive oils. EuropeanJournal of Lipid Science and Technology, 113, 637-643, 587-608.
Comment: Who the f controls this industry?
7kgs of olive stored in plastic bags at 5o C for one week still resulted in olive oils with 35% fewer polyphenols.
Youssef et al. (2011) Influence of olive storage period on volatile compounds and oil quality of two Tunisian cultivars of Olea europea, Chemlali and Chetoui. International Journal of Food Science and Technology 2011, 46, 1245–1252
Comment: While this study was rather unrealistic, it demonstrated how easily prolonged post harvest storage can adversely affect important healthy components in EVOO. Storing olives in 4 tonne bins at ambient temperatures would be expected to have a much greater impact than that observed here.
The Anthracnose pathogen Colletotrichum acutatum in Portugal occurs in 6 geographically variable genetic groups, with 2 groups comprising 92% of populations. The pathogen was stored on leaves, branches, weeds and mummified fruit on the tree. Interestingly, the pathogen was not isolated from fallen mummified fruit. Dispersal occurred by reaching flowers and young fruit via spring rains and by reaching pre-mature fruit via autumn rains.
Talhinhas et al. (2011) Epidemiology, histopathology and aetiology of olive anthracnose caused by Colletotrichum acutatum and C. gloeosporioides in Portugal. Plant Pathology 60, 483–495.
Comment: A great paper. So much solid data in this, a paragraph review doesn’t do it justice.
Washing olives with mill waste water to increase microbiological populations on the skins by 1,000 fold prior to milling resulted in oils with lower oleuropein derivatives (a class of polyphenols), chlorophylls and free fatty acids.
Vichi et al. (2010) The activity of healthy olive microbiota during virgin olive oil extraction influences oil chemical composition. Journal of Agricultural and Food Chemistry. 2011, 59, 4705–4714.
Comments: Unless I’ve missed something, the authors’ claim that increased microbiological load on the olive adversely affects the volatile profile of the resultant oil is unsupported by the data. The counterintuitive result that higher micro loads produces lower free acidity was unexplained, as was the fact that while some of the major polyphenols were significantly reduced. the perceived bitterness and pungency of the oils were largely unaffected. I also disagree with the authors’ interpretation that microbiological load had a greater effect on oil quality parameters than did malaxation time and temperature.
ok not new but interesting nevertheless……
Analysis of charcoal from 3 Mediterranean sites in France and Spain (Cova de l’Esperit, Montou and Cova de les Cendres) showed 3 distinct phases of wild olive exploitation. 1) Harvesting of twiggy wood by hand for heating in the Mesolithic (4,500 BC), 2) harvesting mature wood using tools for land clearing and heating in the Neolithic (4,400 BC) and 3) (again) immature wood harvesting, most likely the result of pruning for olive oil production in the Neolithic to Bronze age (3,300-1,700 BC).
Terral (2000) Exploitation and management of the olive tree during prehistoric tmes in Mediterranean France and Spain. Journal of Archaeological Science 27, 127–133.
Re: the Pardo et al study finding high levels of wax, ECN ratios, and stigmastadienes: while it’s entirely reasonable to think that this is the result of adulteration, a previous study (for which I assume the same data are presented in this full-text paper (scroll down)) found that Argentinian Arbequina olive oils from farms and mills in the hotter parts of the country quite routinely deviated on these same parameters. The two explanations (fraud and natural variation) are not exclusive as explanations of the variability either at the mill or in the store, but it seems likely from the Ceci et al report that the latter is the more likely explanation.
Genomic techniques are, increasingly, looking like the only way to guard against seed oil adulteration without falsely convicting honest farms with unusual (non-Mediterranean) climates and cultivars, as you’ve pointed out before.