New Method Based on Polarity Reversal for Detecting Adulteration of Extra Virgin Olive Oil with Refined Olive Pomace Oil

Abstract

Extra virgin olive oils (EVOO) are vulnerable to adulteration. Thus, a rapid and cost effective screening method is required to detect adulteration. This study develops a method for detecting EVOO adulterated with refined olive pomace oil (ROPO) based on polarity reversal method (PRM). A device is designed based on PRM to determine current of oil sample. Adulteration is detected according to the current difference between EVOOs and ROPOs caused by the content discrepancy of polar compounds. Polar phenolic components are characterized by high performance liquid chromatography-mass spectrometry and Folin-Ciocalteu assay to confirm the principle of the proposed method. Calibration, validation, and blind sample validation is performed. Results showed that current of EVOOs is higher than that of ROPOs due to richer and higher content of polar phenolic compounds. Calibration of 5-90% adulteration with R 2 = 0.997 is established. The R 2 of validation and blind sample validation are close to 1. The relative standard deviation of 5-90% adulterated samples and ROPO is 4.76%, indicating good accuracy and precision. Practical Applications: The proposed method can obtain adulterated ROPO content by simply referring the calibration curve of current within 10 min without pretreatment, which can be used in quick test for industry and retailers.