Diced tomatoes are the closest to fresh tomatoes; toss them into pasta salad, guacamole, or quick-cooking sauces. Add garlic, pepper, and oregano to crushed tomatoes and tomato sauce for an easy pasta sauce. Whole peeled tomatoes, which break down during long cooking times, are ideal for soups, stews, and meat sauces. Tomato paste is highly concentrated and generally used only as a thickener and flavor enhancer in sauces, soups, and stews. A little bit of the paste goes a long way, so use conservatively.
Canned tomatoes have even more health benefits than fresh tomatoes. Lycopene, a pigment that is responsible for the tomatoes' red color, is one of several carotenoids (a group of antioxidants) that may help to decrease the risk of heart disease and certain cancers. The processing method used in canning tomatoes causes the release of a greater amount of lycopene than what is usually found in raw tomatoes.
Like most canned goods, tomato products have a long shelf life. As long as they are unopened, they will keep in the pantry for up to a year. Once a can is opened, however, the contents should be transferred to a glass or plastic storage container (to prevent it from taking on a metallic taste) and refrigerated for no more than one week. You can freeze leftover tomato paste in an ice-cube tray. Once frozen, pop the cubes into a resealable plastic bag; they'll keep up to six months.