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Alkyl-esters are not a solution but another small step

The EU rule draft is ready. For someone it is the solution to defeat the deodorized. True or false? Here is the truth thanks to the contribution of experts from the Italian Society of Fatty Substances



Until a few years ago the threat to the extra virgin olive oil was the fraudulent addition hazelnut oil, much cheaper and good for easy and illegal profits.
Today the enemy’s name is deodorized.

Low quality oils with moderate organoleptic defects can be deodorized through physical-chemical processes and miraculously transformed in extra virgins. From bad and cheap raw material, an extra virgin can be derived by means of low cost and easy technological transformations. This fraud is hard to discover.
Chemical analyses cannot, officially, discover a deodorized oil, since no method or marker is adequate to the purpose, although the correlation between several parameters can give hints to the more expert chemists. For a law, this is not enough, as limitations, methods and markers are necessary: hence, the chase for the perfect system. Great hopes were put in the alkyl-esters. Who are they? These compounds are formed through fermentation and degradation processes of low quality olives, which entail the production of methyl- and ethyl- alcohols and the formation of fatty acids from triglycerides, followed by an esterification reaction. A concept to emphasize is the low quality, which allows to better understand the discussion and conclusions drawn at then end of the study sessions of the Italian Society for the Study of Fatty Substances, in the fiftieth anniversary of their foundation.

Photo by Lorenzo Cerretani

The certainties
It is now clear that the presence of alkyl-esters depends on the quality of olives. The over-maturation, with its damaging effects on the cells, increases the content in free fatty acids and the delivery of methanol by degradation of pectins present in the cellular structures of the drupe, that is the substances that precede the formation of alkyl-esters. Similarly, a bad preservation of the olives increases the content in free fatty acids and the delivery of ethanol and methanol through fermentation.
Once determined that the presence of alkyl-esters does not depend on the duration of the preservation of an oil, if the olives are of goof quality, a “soft” (mild temperature conditions) deodorization does not significantly vary the concentration of the alkyl-esters in the oil.
Deodorization markers?
It is not correct to define the alkyl-esters as markers of the deodorization, although the raw material may produce low quality deodorizers and there is a probable correlation between a high content in alkyl-esters and a deodorized oil. Quality parameters Since alkyl-esters can identify low quality olives which will produce low quality oils, which cannot be classified as extra virgin oils, the International Oil Council has decided to include them among the analytical parameters to discriminate the class of oils, since November 2009.

Considering the different productive structures and used agronomic and management techniques, Italian and Spanish researchers had to reach a compromise at 75 mg/kg for the legal limit of alkyl-esters contained in an oil, or between 75 and 150 mg/kg when the ratio ethyl-esters/methyl-esters is not higher than 1.5.

Such value, and the method to determine it, is going to be included in the new rules by the European Union.
Hard life for cheaters
The introduction of a new analytical parameter, although not being the solution to the problem of deodorization, is certainly a little but important parameter to guarantee the quality and genuineness of extra virgin olive oils.

by Alberto Grimelli
06 december 2010, Technical Area > Olive & Oil

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