Nitrogen testing could aid organic certification

According to the Journal of Agricultural and Food Chemistry , recent testing at the University of East Anglia's Institute of Food Research has found a notable variance in the levels of nitrogen isotopes composition in some conventional and organic crops, which could be used to better identify the validity of organic foods.

Organic certification is becoming an increasingly important issue in food production, not least for the growing number of organic producers and products keen to capture public confidence that their products meet standards that are being promised.

As such, the study collected commercial organic and conventionally grown tomatoes, lettuces, and carrots, ascertain whether organic and conventionally grown materials are systematically different in the levels of nitrogen isotope they contain.

By looking into the respective variances of the rarer 15 N nitrogen isotope in vegetables, the tests sought to indentify any profound differences realting to food porduction methods.

The research, led by Simon Kelly, attributes the variances to the use of synthetic nitrogen fertilisers that are prohibited for use in organic production.

Non-organic nitrogen based fertilisers - which are derived from the atmosphere - were found to have relatively stable isotope values between minus two and two percent Conversely, organically viable alternatives like manure, which according to the report are the most commonly used non-synthetic fertiliser, have a much larger 15 N values.

These values are often recorded with a nitrogen value of around 10 per cent - 20 per cent.

Though other organic fertilisers had not been as extensively tested, the findings indicated that they were still likely to differ from synthetic products due to the more diverse nature of their origins.

Despite variable factors of organic food production including soil types and atmospheric conditions, fertiliser type was seen as the only factor that affect the presence of nitrogen isotopes in a product.

Organically grown tomatoes on average were found to have nitrogen isotope levels some 8.2 per cent higher than in conventionally grown samples of the product.

This correlated with similar testing on lettuces, which while having higher nitrogen isotope levels in organic samples; saw some overlap between both sets of results.

It was in the tested samples of carrots found that some limitations with the testing were found though.

Results of organic and conventionally grown carrots were found to completely overlap, finding no discernable patterns between the two sets of samples.

This was linked to the lower nitrogen requirements of carrots.

While the findings did show some inconsistencies, the research concluded that testing for nitrogen isotopes did have benefits as part of wider testing process for fraudulent organic claims on food and beverage products.

"We strongly advocate that end product tests such as the nitrogen isotope approach cannot and should not be thought of as a replacement for organic certification and inspection schemes," the report concluded.

"However, it is our view that any analytical techniques that assist in protecting consumers from fraud and help to protect the interests of all honest growers should be viewed positively."

At last weeks 35 th meeting of the Codex Committee on Food Labelling, organic certification was found to be one of the most pressing issues facing food labellers.

Source: Journal of Agricultural and Food Chemistry Volume 55, Pages 2664 - 2670 "Nitrogen Isotope Compostion of Organically and Conventionally Grown Crops" Authors: A. S Bateman, S. D Kelly, and M. Woolfe