Ketchup made from organically grown tomatoes contain higher levels of beneficial antioxidant compounds – like polyphenols – than ketchup made from conventional tomatoes, say researchers.
The study – published in the Journal of Agricultural and Food Chemistry – analysed the biochemical and metabolomic make up of a range of organic and conventional branded ketchups. The metabolite profiling led to a distinction of features that differentiate between organic and traditionally grown ketchups, said the researchers.
The Spanish research team, from the University of Barcelona, identified key nutrients that have the greatest impact on the overall profile of organic ketchups compared to standard ones.
“Other studies have used metabolomics to analyse alterations in tomatoes caused by mutations. By applying this methodology to our study, we were able to make the first observations of differences in biomarkers between commercial ketchups made from organic and conventional tomatoes,” said Anna Vallverdú-Queralt – the first author of the study.
“We conclude that polyphenols are the main differential markers between products containing organically or conventionally grown tomatoes,” she added.
Organic vs Conventional: Controversial
The fundamental differences between organic and conventional agricultural systems are in fertilization strategy and soil fertility management, which in theory affect the nutrient composition in plants and provide healthier better tasting produce.
However, years of research investigating the nutrient content of plants grown using the two systems have generated largely contradictory results.
In 2009 an FSA review investigating the nutritional content of organic and conventional produce sparked controversy after it concluded that there was no difference. The FSA research concluded: “there is no evidence to support the selection of organically produced foodstuffs to increase the intake of specific nutrients or nutritionally relevant substances.”
But, a second review published by the French food agency AFSSA completely contradicted the findings of the FSA, concluding that “organic plant products contain more dry matter and minerals – such as iron and magnesium – and more antioxidant polyphenols like phenols and salicylic acid.”
Several smaller studies have since backed up the findings of the AFSSA review by reporting higher levels of certain nutrients in organically grown produce including strawberries , whilst a recent study found organic tomato juice to be more nutritious than those grown in the standard commercial way.
The Spanish research team used an untargeted metabolomic approach to detect and analyse several hundred metabolites in each ketchup sample simultaneously. The findings were then compared for differences and similarities.
The results of the analysis revealed that ketchup made from organically grown tomatoes contained higher levels of polyphenolic compounds including flavonols, flavanones and phenolic acids. These biologically active molecules have strong antioxidant and protective effects in the human body and have been linked with several health benefits, noted the team.
In contrast, Vallverdú-Queralt and her colleagues found that ketchup made from tomatoes grown using conventional methods had higher levels of nitrogen compounds.
“In this type of ketchup we have found a greater quantity of nitrogen-rich molecules – the dipeptides glutamylphenylalanine and n- malonyltryptophan,” said Professor Rosa Lamuela-Raventos, head of the natural antioxidant group at the university, and coordinator of the study.
“The fact that conventional crops are fertilized with soluble nitrogen could explain why larger quantities of nitrogen-rich biomolecules are detected, which are fundamental in the synthesis of amino acids and proteins,” explained Vallverdú-Queralt.
The team added that they believe that organic techniques used in the cultivation of crops –in which it does not receive any artificial nutrients – could activate natural defence mechanisms in the plant, resulting in higher levels of antioxidants in the fruit.
Source: Journal of Agricultural and Food Chemistry
Volume 59, Issue 21, Pages 11703–11710, doi: 10.1021/jf202822s
“A Metabolomic Approach Differentiates between Conventional and Organic Ketchups”
Authors: A. Vallverdú-Queralt, A. Medina-Remón, I. Casals-Ribes, M. Amat, R.M. Lamuela-Raventós