Health-promoting substances and heavy metal content in tomatoes grown with different farming techniques

Background  Organic farming is a production technique that imposes major restrictions on the use of fertilizers, pesticides, feed additives and veterinary drugs and for this reason consumers perceive organic foods to be healthier. The content of health-promoting molecules such as ascorbic acid, β-carotene, lycopene and salicylic acid are important aspects of the nutritional quality of organic foods.

Aim  To evaluate health promoting substances and the heavy metal content of tomato berries grown using conventional, integrated pest management (IPM) and organic farming techniques.
Methods  Moisture was determined by drying, crude protein by the Kjeldhal method, and ashes by incineration at 550°C. Ergosterol, ascorbic acid, β-carotene, lycopene and salicylic acid were determined by HPLC. The levels of heavy metals were measured by atomic absorption spectroscopy.

Results  Compared to crops grown using conventional and IPM methods, organic tomatoes contained more salicylic acid but less vitamin C and lycopene. Organic tomatoes had higher Cd and Pb levels but a lower Cu content. Organic fruits had a slightly higher protein content than conventionally cultivated fruits, but the difference was minimal and consequently the nutritive significance was poor.

Conclusions  Farming techniques may have an impact on the quality of tomatoes. Their higher salicylate content supports the notion that organic foodstuffs are more wholesome. However, the lower lycopene and ascorbic acid levels of organic tomatoes are not to be regarded as positive. No residues of pesticides and ergosterol were detected.