Different agricultural management models, comprising a range of cultivation and fertilization techniques that vary between organic and conventional crops, can affect the nutrient content of agricultural and commercial products. According to the new study, the agricultural system in which tomatoes are grown affects the levels of bioactive compounds and other metabolites found in commercially available ketchups.
Metabolomics is pushing back the frontiers of research into the biomolecules in biological and ecological systems. The first author of the study, Anna Vallverdú-Queralt, explains that, “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. We conclude that polyphenols are the main differential markers between products containing organically or conventionally grown tomatoes.”
The results show that ketchup made from organically grown tomatoes contains higher levels of the polyphenolic compounds flavonols, flavanones and phenolic acids, biomolecules with antioxidant properties and protective effects in the human body. In contrast, ketchup made from conventional tomatoes shows higher levels of nitrogen compounds, essential for the synthesis of proteins and other biomolecules: “In this type of ketchup we have found a greater quantity of nitrogen-rich molecules - the dipeptides glutamylphenylalanine and n- malonyltryptophan,” explains Rosa M. Lamuela, head of the Natural Antioxidant Group and coordinator of the study.
The researchers believe that the techniques used in the cultivation of ecological crops -in which the plant does not receive any artificial nutrients - could activate natural defence mechanisms, increasing levels of polyphenols in the fruit. According to Anna Vallverdú-Queralt, “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.”
The experts involved in the study, from the UBʼs Natural Antioxidant Research Group, are affiliated to the Spanish Biomedical Research Centre-Physiopathology of Obesity and Nutrition (CIBERobn) and the Generalitatʼs Food Technology Reference Network (XaRTA). The group works on various research areas including polyphenolic food components, the bioavailability of these molecules and their effects on human health, and has recently published a study in which higher levels of polyphenols were detected in organic tomato juice than in juice from conventionally grown crops (Food Chemistry, 130 (2012) 222-227).
Vallverdú-Queralt, A.; Medina-Remón, A.; Casals-Ribes, I.; Amat, M.; Lamuela, R. M. “A metabolomic approach differentiates between conventional and organic ketchups”. Journal of Agricultural and Food Chemistry, 2011, 59 (21), pp. 11703-11710. DOI:10.1021/jf202822s.