New Method Shows Whether Potatoes Are Organic or Not
Researchers at the University of Copenhagen have developed a new approach that helps public agencies and commercial interests combat fraudulently-labeled organic foods, specifically organic potatoes.
By looking at how organic plants are fertilized, the method provides a deeper, more accurate portrayal of whether eco-labeled produce is indeed organic. According to experts, imported organic vegetables and fruit are susceptible to food fraud.
The new method – pioneered by a research group led by Assistant Professor Kristian Holst Laursen - focuses on the isotope signature in a plant by isolating sulfate, a chemical compound that can reveal how a particular plant was grown. Humans, animals, and plants all have isotope signatures that provide information about the environment in which we live and how we live – diets included.
The current means of finding out whether an item is organic or not focus on identifying pesticide residue. According to Kristian Holst Laursen, this method is far from secure. For example, the use of pesticides on a neighboring field or traces from former conventional production on a now organic field can taint crops. Moreover, the analysis of pesticide residues is unable to reveal whether all of the rules for organic production have been complied with, such as the absence of inorganic fertilizers.
"Our method does not reveal whether pesticides have been used, but whether organic plants have been fertilized correctly. As such, the method complements existing analytical controls and, overall, provides a much more detailed picture of the growing history," explains Kristian Holst Laursen.
The new procedure was combined with stable isotope radio analysis of bulk plant tissue and plant-derived nitrate to discriminate between organic and conventional potato (as well as carrot and cabbage) from rigidly controlled long-term field trials and a case study using retail potatoes. It was shown that oxygen isotope ratios of sulphate from organic vegetables were significantly lower compared to their conventional counterparts and the values were directly linked to the fertilization strategy.
The classification power of sulphate isotope analysis was superior compared to known bulk tissue isotope markers and nitrate isotope values. In conclusion, oxygen isotope analysis of plant-derived sulphate represents a promising new method for authentication of organic vegetables.
Kristian Holst Laursen's research group is currently working with the Danish Veterinary and Food Administration and the method is ready for further testing, approval, and use by public agencies and commercial interests.
