Lycopene content and colour of ripening tomatoes as affected by environmental conditions

Tomatoes may have a great impact in the prevention of some types of cancer. This protective effect has been attributed to lycopene. The biosynthesis of lycopene is affected by environmental conditions. If the temperature of the fruits exceeds 30 degrees C, the synthesis of lycopene is inhibited. Strong direct radiation on fruits (similar to 2990 mu mol m(-2) s(-1) for 1.5-4 h) is harmful. In 2002, we investigated the effect of temperature and photosynthetically active radiation (PAR) on lycopene content. Fruit samples were harvested three times during the growing phase. The average lycopene content of harvested fruits, picked on 18 June 2002, reached 64.9 mg kg(-1) of fresh tomato. The fruits gathered on 25 June 2002 contained on average only 35.5 mg of lycopene per kilogram. The average lycopene content from the third harvest (on 9 July 2002) was 68.9 mg kg(-1). The values of PAR varied between 150 and 415 mu mol m(-2) s(-1), so they did not exceed the critical value. The average temperature preceding the second harvest was the highest (28-32 degrees C) and the maximum temperature ranged between 40 and 43 degrees C. This prolonged, extremely high temperature may have caused the low lycopene level in the second harvest. The lycopene content of six ripeness stages, from green to deep red stage, was measured in 2002 and 2003. The accumulation of lycopene accelerates from the pink stage and there is a high correlation (R-2 = 0.92) between lycopene content and colour values (a*/b*). The higher the ratio of a*/b*, the higher was the lycopene content. (c) 2005 Society of Chemical Industry.