Application of Stable Light Isotope Ratios and Trace Element Concentrations for the Authentication of Saffron

Abstract

Fraudulent practices to increase profits by unscrupulous producers in relation to food products has an extensive history with a recent increase in prevalence due to a large international supply chain, complicated trade routes, modern manufacturing infrastructure and the freedom of food trade. “Food fraud” is the encompassing term used to describe these fraudulent practices and can be defined as the intentional tampering or misrepresentation of food products for economic gain. The concerns of government bodies, consumers and producers of this so called food fraud are twofold; firstly there are substantial economic implications to all those involved and secondly minor to severe health issues can arise. As such, a relatively new area of analytical chemistry has been developed to combat food fraud: Food authentication.

One type of food fraud that is becoming increasingly prevalent is the misrepresentation of the origin of a food product. The misrepresentation of geographic origin is economically viable because of differences in price between production areas due to consumer demand. This difference in consumer demand is due to patriotism, quality perception and concerns about quality, health and production methods. As such, one area of food authentication deals with the provenancing of foodstuffs. While multiple techniques have been developed for this area the two which are most commonly utilized due to their robustness and links to the geographic origin of a food product are the measurement of stable light isotope ratios and trace element concentrations. Saffron is a spice derived from dried stigmas of the Crocus sativus plant and is generally used as a food additive for its desirable colour, flavour and aroma. Saffron is currently the world’s most expensive spice and partially because of this distinction has been subjected to many forms of food fraud throughout history, including fraudulent geographical origin claims. Thus, this thesis is concerned with the adaptation and application of stable light isotope ratios and trace elements concentrations for the geographic origin differentiation of saffron. This current study also investigated the application of these techniques for the identification of adulterated saffron. Compound-specific isotope ratios were also investigated to supplement these two techniques for both the differentiation of the spice based on geographic origin and for the identification of adulterated saffron. The applied methods were successful in enabling the determination of the stable light isotope ratios and trace element concentrations of saffron. Applying these techniques to samples from the Khorasan province of Iran and the La Mancha region of Spain, followed by appropriate statistical analysis and interpretation, enabled the differentiation of the measured samples from Iran and Spain. However a much larger database would be required to be built, which contains samples representative of the populations of concern, if the techniques are to be utilized for the provenancing of a sample of completely unknown origin. Regional differentiation of the measured samples from the Khorasan province in Iran proved more difficult. The techniques also show promise for the identification of saffron adulterated with what is suspected to be paper. Preliminary results from compound-specific isotope ratio analysis appear to show promise for both the identification of saffron adulterated with synthetic aroma compounds and as an extra dimension for the provenancing of the spice.