Lycopene which is the pigment that gives tomatoes and watermelon their red color appears to offer a wide range of health benefits. Cultures that consume a diet rich in lycopenes have reduced rates of a range of cancers (especially prostate) as well as improved cardiovascular health. Although there are no specific recommendations as to optimum daily intake of lycopene, Collins and associates (HortScience 2006 vol 41 p 1135-1144) review some the factors that can contribute to a diet rich in this nutrient. Red coloration is a clear indicator of a high lycopene content – think tomato, watermelon, guava, red grapefruit. Yellow or orange varieties of tomato and watermelon largely lack this nutrient. There is considerable variability in the lycopene content of differing varieties of watermelon and tomato – and breeders are beginning to release new lines that have been specifically selected for an elevated lycopene content. A greater appreciation of the importance of lycopene is also driving increased interest in red varieties of carrots. The lycopene content of tomato and watermelon peaks at full maturity and then stays fairly stable during cold storage and the preparation steps typically used for fresh products. While cooking result in substantial loss of the lycopene found in tomato, the lycopene that is left in the cooked product is actually more readily absorbed during digestion that if the tomato was consumed raw. Fortunately, the lycopene in raw watermelon is quite easily absorbed. The rate of degradation of lycopene in frozen products can be minimized by minimizing exposure to air and by keeping the temperature as low as possible.
Source: Collins et al. (2006). HortScience 41:1135-1144