Q01095: Validation of a DNA-based method for the determination of hazelnut oil in olive oil
Monday 8 September 2008
Study Duration: September 2004 to March 2006
Contractor: Campden and Chorleywood Food Research Association
Background
Increasing consumer demand for premium quality and speciality oils can attract fraudulent substitution of expensive oils with similar cheaper products. The premium price attracted by olive oil makes it a particular target for adulteration with less expensive hazelnut oil. In order to protect consumers from this practice a method is required to ensure the authenticity of olive oil and to allow for enforcement of the Olive Oil Marketing Regulation which controls the marketing standard for the selling of olive oil.
Standard analytical techniques are not able to reliably detect low levels of adulteration of olive oil with hazelnut oil due to their chemical similarity. Therefore the suitability of recently developed DNA-based methods needs to be investigated to establish a robust method to detect olive oil adulteration.
Research Approach
An end-point PCR (Polymerase Chain Reaction) method and a quantitative PCR (qPCR) method able to detect unrefined hazelnut oil in olive oil with a limit of detection of 0.5% was developed during a previous FSA funded project [Q01060]. This current project aimed to optimise and validate the developed method for the extraction and detection of DNA from unrefined hazelnut oil in olive oil and prepare an SOP (Standard Operating Procedure) for the method for use by enforcement laboratories.
Results and findings
The optimised assay validated in this study was shown to offer a high level of sensitivity and accuracy for the detection of hazelnut adulteration of olive oil at levels between 2 and 20%. During blind testing using a range of authentic samples from different commercial mills, 96% of samples were correctly classified with respect to the presence or absence of unrefined hazelnut oil. This study has allowed the validation of a DNA-based method for the accurate detection of unrefined hazelnut oil in olive oil, which can in turn be considered better than or at least comparable to current stand methods for detecting the adulteration of virgin olive oil with unrefined hazelnut oil. A validated SOP for this method is available for use.