The team from the Bavarian Health and Food Safety Authority and the Wuerzburg University said that because organic food can fetch prices twice as high as conventionally produced food, there is a risk of fraudulent labelling.
To prevent and detect counterfeit product, there is a strong need for analytical methods that allow the verification of organic cultivation.
Overall, 361 tomato samples of two different cultivars and four different producers were regularly analyzed during a seven month period.
Difference between organically and conventional
The study examined the differentiation between organically and conventionally grown tomatoes involving NMR spectroscopy.
The most reliable analytical method for authentication is through the composition of the nitrogen isotope but there is an overlap between values of organically and conventionally grown crops that suggests developing analytical methods could verify the growing method.
Previous NMR measurements of tomatoes and tomato products focused on carotenoid composition, degree of ripeness, quantitative NMR, magnetic resonance imaging (MRI) measurements, or diverse 2D NMR experiments.
The aim is developing a method for authentication of organic tomatoes against the background of food surveillance and consumer protection, independent from nutritional perspectives.
Numerous fertilizers may be used and fruits can be grown in greenhouses and on open land. It is unfeasible to create an experimental design that fulfills the possible growing conditions in all facets, said the researchers.
Attention was on greenhouse cultivation, and authentic tomatoes were grown conventionally with mineral substrate and mineral fertilizers as well as organically with soil and organic fertilizers.
Significant trend seen
Results of principal component analysis showed a significant trend for the separation between organically and conventionally produced tomatoes.
Linear discriminant analysis demonstrated good discrimination between the growing regimens, and external validation showed 100% correctly classified tomato samples.
At least 250g of tomato was pureed and subsequently stored at −18 °C. After thawing, the samples were centrifuged for five minutes at 3528g, and the residual liquid tomato phase was used for subsequent NMR measurement.
Further validation studies disclosed unexpected differences between individual producers, which interferes with the prediction of cultivation method, yet results indicate significant differences between
Source: Journal of Agricultural and Food Chemistry
Online ahead of print, DOI: 10.1021/jf502113r
Authors: Monika Hohmann, Norbert Christoph, Helmut Wachter, and Ulrike Holzgrabe