The detection of adulterated olive oil

Abstract: The detection of adulteration of olive oil is still a challenge and requires the development of new analytical methodologies. The methods of the international olive oil council (IOC) have been considered for a long time as a good tool for the detection of unpermitted thermal treatment of extra virgin olive oil.

In a new analytical approach, we monitor the structural and oxidative changes of fats and oils during storage at ambient temperature up to 60 °C and thermal treatment at 80 °C up to 220 °C during soft-deodorisation or refining.

Primary and secondary degradation products have been used to monitor the structural changes of the treated and non-treated olive oils.

Statistical analysis of the data by linear discriminant analysis (LDA) based on the analytical parameters revealed that chemical changes up to 60 °C differ from those above 70 °C, and this class again differs from that heated above 130 °C.

This observation allows now a differentiation between changes in olive oils during storage (temperature < 70 °C), during soft deodorization (80-120 °C) or a thermal treatment above 180 °C such as refining. Consequently, the addition of a conventionally refined vegetable oil, soft deodorised olive oil and pomace oil might be distinguished from a virgin olive oil. The statistic method of logit regression is used to detect the addition of adulterated olive oils in virgin olive oil.

This work continues the research published in 2020 by GERTZ et al. (1) The results obtained before were verified by further investigations and substantially expanded. Even, adulteration of virgin olive oil with only 5% refined or soft-deodorized vegetable oil or olive oil can now be detected with a high statistical certainty of 99.4 %.

1) Ch.Gertz, B.Matthäus, I. Willenberg, Eur. J. Lipid Sci. Technol. 2020, 1900355 (1-11)