Ketchup contains the chemicals lycopene, acetic acid and water. The body has an easier time processing lycopene when it comes from the tomato paste in ketchup as opposed to fresh tomatoes.
Lycopene is a naturally occurring chemical found in high amounts in tomatoes, and it also gives the fruit its red color. The chemical is also responsible for the coloring in watermelons, pink grapefruits and apricots. The tomatoes used in producing ketchup are cooked, and cooking has the added benefit of increasing the yield of lycopene. Lycopene from cooked tomatoes is as easy for the body to use as the lycopene found in supplements. Lycopene is used in treatments to prevent heart disease and the hardening of the arteries.
The acetic acid in ketchup comes from vinegar, which is one of the main ingredients involved in making the condiment. Vinegar comes from a bacterial fermentation of ethanol into acetic acid. The acetic acid is then combined with water and artificial flavorings. Household vinegar has an acetic acid concentration of 5 to 8 percent.
Water is a plentiful, naturally occurring chemical found in both the tomatoes and vinegar used to make ketchup. Water is used to increase or decrease the concentration of acetic acid in vinegar and can also be juiced from raw or cooked tomatoes.