How to Select and Store
Choose tomatoes that have rich colors. Deep reds are a great choice, but so are vibrant oranges/tangerines, brilliant yellows, and rich purples. Tomatoes of all colors provide outstanding nutrient benefits. Tomatoes should be well shaped and smooth skinned with no wrinkles, cracks, bruises, or soft spots. They should not have a puffy appearance since that characteristic is often associated with inferior flavor and may also result in excess waste during preparation. Ripe tomatoes will yield to slight pressure and will have a noticeably sweet fragrance.
When buying canned tomatoes, it is often better to buy those that are produced in the United States as many foreign countries do not have as strict standards for lead content in containers. This is especially important with a fruit such as tomatoes, whose high acid content can cause corrosion to, and subsequent migration into the foods of, the metals with which it is in contact.
While on the topic of canning, you may also be interested in some of the most recent information about canned tomato products and BPA (bisphenol A). BPA is an added component in the vinyl lining of numerous canned foods, and it's also known to be problematic from a health standpoint because of its impact on estrogen metabolism. (For more extensive information about BPA, click here.) A recent study of canned foods in Canada has shown an average of about 1 ppb of BPA in canned tomato paste products (with a maximum amount of about 2 ppb), and an average of 9 ppb in pure tomato products liked diced, sliced, or whole peeled tomatoes (with a maximum amount of about 23 ppm). While the U.S. Food and Drug Administration has not set a limit on the amount of BPA allowed in canned tomatoes, the European Commission Directive for BPA has set a limit of 600 ppb. While any amount of BPA in canned tomatoes seems undesirable, we are glad to see that the BPA levels were fairly low in this recent study, especially in canned tomato paste products. You'll need to look for a claim of "BPA-Free" on the label of your canned tomato products (or call the manufacturer) if you want to be sure that your canned tomatoes contain no BPA, since even some certified organic canned tomato products may contain—and are allowed to contain—BPA (through migration from the can).
Since tomatoes are sensitive to cold, and it will impede their ripening process, store them at room temperature and out of direct exposure to sunlight. They will keep for up to a week, depending upon how ripe they are when purchased. To hasten the ripening process, place them in a paper bag with a banana or apple since the ethylene gas that these fruits emit will help speed up the tomato's maturation. If the tomatoes begin to become overripe, but you are not yet ready to eat them, place them in the refrigerator (if possible, in the butter compartment which is a warmer area), where they will keep for one or two more days. Removing them from the refrigerator about 30 minutes before using will help them to regain their maximum flavor and juiciness. Whole tomatoes, chopped tomatoes and tomato sauce freeze well for future use in cooked dishes. Sun-dried tomatoes should be stored in an airtight container, with or without olive oil, in a cool dry place.
Ketchup can be a surprisingly good source of tomato nutrients, including lycopene. But if you are going to purchase tomatoes in the form of ketchup, we recommend that you choose organic ketchup. We make this recommendation not only because you're likely to avoid unwanted pesticide residues and other contaminants if you purchase organic, but also because we've seen a recent study showing higher lycopene content in organic versus non-organic ketchup.