Background and methodology:
Tomato (Lycopersicon esculentum) is one of the most popular vegetable crops. It contains not only health-promoting secondary metabolites such as carotenoids, lycopene, β-carotene, and vitamin C, but also natural toxins such as glycoalkaloid α-tomatine,and dehydrotomatine. At higher doses, glycoalkaloids exhibit mainly two toxic actions in exposed mammals: membrane disruption activity affecting the digestive system and anticholinesterase activity on the central nervous system. This study compared the content of both health-promoting and toxic components in tomatoes cultivated in organic farming and farming that uses mineral fertilizers. Four different fertilization regimes were employed: the control (using no fertilizers, mineral or organic), organic farming (using a slurry fertilizer), mineral farming (using ammonium sulphate and potash fertilizer) and a combination of mineral and organic fertilizers.
Findings:
The content of natural toxins glycoalkaloids α-tomatine and dehydrotomatine ranged from 0.85 to 4.84 mg/kg and from <0.02 mg/kg to 0.24 mg/kg, respectively. The highest levels were found in tomatoes from mineral farming and lowest in organic tomatoes. The 'Start' variety tended to contain slightly higher levels of these natural toxins. No significant differences among the various systems were found in the levels of health-promoting compounds in the fruit. The content of biologically active compounds in tomatoes is strongly influenced by their maturity. There is a rapid increase of major tomato carotenoids, lycopene, and β-carotene that takes place during ripening and, simultaneously, a significant decrease of glycoalkaloids,
α-tomatine,and dehydrotomatine. The lycopene content in ripe tomatoes was 117 times higher compared to green fruit; on the other hand, α-tomatine levels in this unripe fruit were 43 time higher than in red fruits. Vitamin C content was highest in ripe tomatoes.
Reference:
Schulzova, V., and Hajslova, J. (2007). Biologically active compounds in tomatoes from various fertilization systems. Poster presented at 3rd Quality Low Input Food (QLIF) Congress: Improving Sustainability in Organic and Low Input Food Production Systems. University of Hohenheim, Germany, March 20-23. Available on-line at: http://orgprints.org/9872/