Isotopic characterization as a screening tool in authentication of organic produce commercially available in western North America

Abstract

The use of nitrogen stable isotopes to discriminate between conventionally and organically grown crops has been further developed in this study. Soil and irrigation water from different regions, as well as nitrogen fertilizers used, have been examined in detail to determine their effects on nitrogen isotope composition of spinach, lettuce, broccoli and tomatoes. Over 1000 samples of various types of organically and conventionally grown produce of known origin, along with the samples of nitrogen fertilizers used for their growth, have been analysed in order to assemble the datasets of crop/fertilizer correlations. The results demonstrate that the developed approach can be used as a valuable component in the verification of agricultural practices for more than 25 different types of commercially grown green produce, either organic or conventional. Over a period of two years, various organic and non-organic greens, from different stores in Seattle (WA, USA) and Victoria (BC, Canada), were collected and analysed using this methodology with the objective of determining any pattern of misrepresentation.

Using Nitrogen Stable Isotopes to Authenticate Organically and Conventionally Grown Vegetables: A New Tracking Framework

“…The organic and conventional zucchini samples showed an average δ 15 N value of 5.54 ± 1.10‰ and 2.14 ± 1.64‰, respectively, a higher range of variation being observed for the organically grown vegetables (Table 2). The results from the conventional cultivars were in accordance with those found by previous authors [19,20], who reported respective mean δ 15 N values of 2.32 and 2.40‰, but differed from the values obtained for the organic zucchini samples (above 9‰ in both studies). However, despite the lower differences in the δ 15 N composition between the organic and conventional samples found in our study, we observed statistically significant differences between both cultivars' regimes, although supported by a lower p-value (0.01 > p > 0.05) than those found in the remaining vegetables analysed (p < 0.001).…”

“…However, the discrimination was less satisfactory for slow-growing vegetables (more than 80 days), hypothesizing that 15 N could be taken by soil microorganisms in situ, reducing the ∆ 15 N between the organic and conventional samples. Another study [20] examined soil, irrigation water, and nitrogen fertilizers used in different conventionally and organically grown crops to determine their effects on the nitrogen stable isotopes of spinach, lettuce, broccoli, and tomatoes. The authors of this study found differences in the δ 15 N of these cultivars according to their organic or conventional management.…”

Multi‐isotopic signatures of organic and conventional Italian pasta along the production chain

“…In particular, ratios of stable nitrogen isotopes (δ 15 N) in the bulk tissue or in isolated chemical compounds of the foodstuff (e.g. nitrate) have been investigated mainly in fruits and vegetables to detect differences between organic and conventional products . This approach is based on the fact that the nitrogen isotopic composition of synthetic fertilizers, widely used in conventional farming systems, is generally causing lower δ 15 N values compared with animal manures and composts often used in organic systems .…”

“…nitrate) have been investigated mainly in fruits and vegetables to detect differences between organic and conventional products. [15,[18][19][20][21][22][23] This approach is based on the fact that the nitrogen isotopic composition of synthetic fertilizers, widely used in conventional farming systems, is generally causing lower δ 15 N values compared with animal manures and composts often used in organic systems. [24] However, different conclusions have been reached in these studies as a consequence of highly different experimental conditions including variation caused by plant species, food products, growth conditions, fertilizer types and application rates and experimental designs.…”

Effect of Organic Food Intake on Nitrogen Stable Isotopes

“…The lowest δ 15 N value for conventional farming was observed in a batch of tomatoes and was of −2.5‰ [ 15 ] while the highest value, 8.72‰, was observed in peppers [ 19 ] ( Table S1 ). For organic agriculture, the lowest δ 15 N value, 0.3‰, was measured in peas obtained from an organic grocery store [ 20 ] and the highest δ 15 N values, 21.89‰, in lettuce fertilized with bat guano [ 21 ] ( Table S1 ).…”