Qualitative and quantitative markers to identify the quality and adulteration of olive oil with rapeseed oil

Abstract

The objective of this study was to develop a rapid and convenient chromatographic method for authenticity control of vegetable oils using the total sterol profile determined by gas-chromatography (GC) with flame ionization detector (FID). Two pure oils, rapeseed and olive oil, processed by minimal technologies (cold pressing) in Romania and an adulterated olive oil with 40 % of rapeseed oil were used as sample matrices in the method development. The rapeseed oil can be identified by the presence of brassicasterol (see peak number 2 in Figure 2.) which is characteristic mainly for this oil. In olive oil, this sterol is absent. The concentrations of b-sitosterol, campesterol and brassicasterol as well their ratios can identify the adulteration of virgine olive oil with rapeseed oil. High ratios b-sitosterol/ campesterol are specific to virgin olive oil (~ 27.5) while these ratios are low (~2) for rapeseed oil or adulterated olive oil. Also the ratio campesterol / brassicasterol can indicate the adulteration. This ratio is low (~2) for rapeseed oil and higher (~ 4.8) in extra virgin olive oil. Adulteration of olive oil with rapeseed oil determine the decrease of this ratio. In this work we report three ways to identify the quality and authenticity of olive oil. We found as well markers which indicate if the olive oil was adulterated with rapeseed oil.