Fraud investigation in the extravirgin olive oil supply chain : Identification of vulnerable points and development of novel fraud detection methods

Abstract

With the globalisation of the food supply system, food fraud can have international impacts, sometimes with far-reaching and lethal consequences. Extra virgin olive oil (EVOO) is considered one of the most frequently reported commodities, suffering from fraud. Knowledge about risk factors and precise laboratory and broad on-site screening methods will help to combat fraud in the EVOO supply chain network. The main objectives of this thesis are to develop strategies to combat fraud in the EVOO supply chains through knowledge about weak spots and underlying risk factors and the development of novel detection methods. To achieve these goals, firstly, the EVOO supply chain was assessed for their vulnerability using the SSAFE food fraud vulnerability assessment tool. These assessments indicate that the EVOO supply chain is fairly vulnerable. B2B companies and retailers in the EVOO supply chain are more vulnerable to fraud than olive oil producers and food manufacturers due to the additional vulnerability related to opportunities in time and place and a lack of control measures. Fraud vulnerability across the EVOO supply chain was not only determined by the place of the actor in the chain (node), but also by the scale and location of the companies. Four novel methods were developed in this thesis for EVOO authentication. Monochloropropanediol (MCPD) esters and glycidyl esters (GEs) analysis by gas chromatography-tandem mass spectrometry (GC-MS/MS) was applied to defect EVOO adulteration with lower grade oils. The limit of fraud detection of lower grade olive oils in EVOO was 2% when using 3-MCPD esters, 5% for 2-MCPD esters and 13–14% for GEs. These results imply that the method is fairly useful for confirmatory analysis. However, 3-MCPD analysis by GC-MS/MS is currently a tedious and time-consuming method, it is not recommended to use this method to analyse a large number of suspect samples when a quick response is required. In addition, three rapid and non-destructive techniques were developed. The volatile organic compounds (VOCs) fingerprint analysis by proton transfer reaction-quadrupole ion guide time of flight-mass spectrometry in combination with multivariate statistics proved to be a promising screening methodology for the distinction of EVOO from its lower grade counterparts, as well as from other vegetable oils that are potential adulterants. In the one class classification evaluation, the k-nearest neighbours model presented the best results, which showed that more than 95% of oil samples were correctly predicted. For this most successful model, formic acid, dimethyl sulphide and hexenal are key compounds for the distinction of EVOO from the other oils. Except for the VOCs analysis, the spectral analysis by handheld near infrared spectroscopy combined with multivariate statistics also proved to be good methodology to discriminate EVOO from its lower grade counterparts. The EVOO samples were 100% correctly identified. Pomace olive oil (POO) was efficiently discriminated from EVOO, but 7% of the refined olive oil samples were predicted incorrectly. Furthermore, it was found that the relevant spectral information for the distinction of the oils strongly correlated with the degree of unsaturation of the oils as well as their levels of chlorophylls, carotenoids and moisture. In addition, a newly developed ultrasonic pulse echo system appeared to be a rapid and non-destructive method for the characterisation of vegetable oils. The ultrasonic velocity of EVOO differed significantly from those of POO and the oils of other botanical origin, but not from the velocity of refined olive oil. Furthermore, it was found that the underlying reason for the ultrasonic velocity differences between oils was the variation of the density and viscosity of the oils. In conclusion, this study shows that the intermediaries between producers and consumers are more vulnerable to fraud due to the opportunities to commit fraud, as well as the greatest lack of adequate food fraud control measures. The results of this thesis also show that the newly developed methods cannot easily to be circumvented by fraudsters and they can be effectively applied for the distinction of EVOO from its lower grade counterparts and some vegetable oils. The insights in the weak spots in the EVOO supply chain network in combination with the newly developed fraud methods add to and reinforce the strategies to combat fraud in the EVOO supply chain. This all will help to ensure that consumers get what they are paying for and to fight unfair competition.