Osservazioni preliminari riguardo alla variazione di alcune caratteristiche chimiche di oli vergini da olive sottoposti a processi di deodorazione “soft”

Preliminary observations on the change of some chemical characteristics of virgin olive oils subjected to a “soft deodorization” process adulteration of virgin and extra-virgin olive oils is an on going issue that is of particular interest to the regulating bodies investigating fraud. unfortunately mass control of olive oils on the commercial market is impossible therefore adulteration is rife and unnoticeable. Nowadays the most problematic type of fraud is by way of reducing or eliminating unpleasant odours which are a real defect, or unwanted odour compounds originating from the geographical origin of the olive cultivar. if an adulterated oil is put on the market as a virgin oil, or if it is mixed with other oils and sold as virgin oil, it is difficult to identify the fraud when the adulteration is carried out under bland conditions “soft deodorization”. Soft deodorization seems to be carried out in different ways: a sort of molecular distillation under vacuum or in a stream of nitrogen at low temperatures, or using absorbent powders, or using filtering membranes. in all these cases the composition of the volatile or polar compounds would be unbalanced (adsorbed more than the oil thanks to the use of high polarity powders), or there would be a selective loss of compounds of a certain dimension (through the use of the filtering membranes). In our opinion the analyses that could reveal such fraudulent treatments are: the determination of volatile compounds by means of SPME/GC that can show the reduced amount of volatile molecules: the decrease of the amount of water present in the micro-emulsion of the oil, following the “stripping” or by adsorption mechanisms.