Tomatoes: Safe Methods to Store, Preserve & Enjoy
What is a Tomato?
The common garden tomato (Lycopersicon esculentum Mill.) is botanically classified as a fruit. Actually it is a berry, but many people think of it as a vegetable. The U.S. Department of Agriculture, for example, has defined it as a vegetable. The modern tomato originated in the southern regions of the Andes Mountains, the coastal deserts of Peru, and Ecuador and parts of central Mexico. By the time Europeans arrived in the New World, tomatoes were already widely cultivated by the Aztecs as far north as Mexico. The Aztec (Nah’uatl) word tomatl is a term that roughly translates as “plump fruit.” In the early 16th century, Spanish explorers changed tomatl to tomate.
Tomatoes are low in calories and a good source of Vitamins A and C. California produces about 30 percent (5000 to 6000 tons per year) of U.S. fresh markettomatoes, and about 95 percent (8 to 11 million tons per year) of tomatoes used for processing. Tomatoes grown in California are harvested from May to December, with peak periods from July through mid-August. The United States imports greenhouse tomatoes year-round from Canada, Mexico, and the Netherlands. Field tomatoes are imported from Mexico from December through April. The flavor, texture, and cooking characteristics of tomatoes depend on the variety, growing method, local environment, and handling techniques used during and after harvest. Because processing and fresh-market tomato varieties are used in very different ways, they have been bred and selected for traits important to their specialized growing, harvesting, shipping, processing, and consumption requirements.
GROWING TOMATOES IN THE HOME GARDEN
There are more than 400 varieties of tomato—including hundreds of specialty and heirloom types—that are suited for growing in the home garden. You can choose the varieties that work best in your area if you want to maximize productivity. For more on varieties: Preserving the Season_Tomatoes
SELECTING TOMATOES FROM THE HOME GARDEN
Tomato eating quality is largely a matter of personal preference. Normally, tomatoes are harvested from the vine when fully colored (red, yellow, purple, multi-colored, etc.) but still firm. When the first signs of color appear, typically at the blossom end, the tomato is mature and edible, but not fully ripe. By the time a tomato reaches about 20 percent of full-ripe color, it has reached its full balance of sweetness and acidity potential. Peak flavor for the variety can develop on or off the vine from this point onward, with proper handling. Generally, fruit is left on the vine until at least 80 percent of its ripe color has developed.
Tomatoes harvested with 60 to 80 percent of full color can be ripened in the kitchen. The optimal method is to place the fruit in a ripening dome or paper bag (not plastic) out of direct sunlight to maintain the right balance of humidity. Cherry tomatoes are best when picked at about 85 to 95 percent of full color. If left on the vine until fully ripe, they tend to over-soften or crack.
SELECTING TOMATOES AT RETAIL
At least 10 types of tomatoes are marketed at U.S. retail outlets. They are grown using conventional, organic, and greenhouse methods. The key factors for selecting tomatoes at the market are hard to generalize, since they vary depending on intended use and personal preference. Here are a few guidelines, though, for judging firmness, texture, and flavor of tomatoes for use in salads and sandwiches.
- Tomato skin should appear bright and well colored for the type of tomato. At retail, red tomatoes should have at least some red color for best eating. Light pink tomatoes may ripen further at home after 2 to 3 days and achieve a flavor quality comparable to that of vine-ripened fruit of the same variety. Pale pink tomatoes that have been mishandled by being held too cold for too long, however, will never properly ripen. Yellow tomatoes should have a medium yellow hue, rather than a deep yellow or yellow-orange color that indicate over ripening.
- Fruit should be firm or should yield slightly (depending on your preference) when gently squeezed with the fingertips. No deformity should be visible when you release pressure.
- Fruit surface should not wrinkle when you slide your thumb, with slight
pressure, from blossom-end to stem-end. Tomatoes should be free of darkened or bruised areas under the skin, which may be signs of mishandling and may make the tomatoes unusable after cutting.
- For cluster “vine-ripened” tomatoes, select firm tomatoes attached to bright green, flexible vines (i.e., vines that can bend slightly without breaking) for peak flavor and texture. Vines that have become dull and dehydrated may still hold fruit of good to excellent eating quality. Bright red color and overall firmness of the fruit, rather than vine color, are the best indicators of freshness.
STORING FRESH TOMATOES
If purchased from a retail outlet, most ripe tomatoes retain best eating quality for 2 to 3 days if stored at room temperature. Store fruit away from direct sunlight with the stem scar facing up to reduce softening and darkening of the fruit. You can hold under-ripe tomatoes from a retail outlet for as long as 5 days. For short-term storage, it is best to keep the tomatoes in a well-vented ripening dome or a paper bag at the coolest room temperature possible. Be sure to keep the fruit out of direct sunlight as it will warm the fruit and cause more rapid softening.
Many tomato varieties have been bred to enhance traits that extend the fruit’s storage life, including some large-fruited “vine-ripe” types, cluster tomatoes, and many cherry and Roma types. They may be held at room temperature for up to 5 days.
Refrigeration is not usually recommended for fresh tomatoes as it can cause flavor loss. You can, however, delay softening of “just-ripe” tomatoes by holding them for a short time in refrigerated storage. Flavor loss will be minimal if cold storage lasts less than 3 days. If you need to refrigerate tomatoes, place them in the crisper section in their plastic clamshell container (if that is how they were packaged in the store), a paper bag, or a plastic bag with a few slits, to reduce water loss. This is most important for cherry and grape tomatoes. Excessive water loss is first noticeable as wrinkling or puckering of the fruit’s skin. It is best to remove the fruit from the refrigerator 1 hour before eating to help it regain some of its original flavor.
SAFETY TIPS FOR HANDLING FRESH TOMATOES
On occasion, tomatoes have been linked to foodborne illness caused by Salmonella bacteria. Like any other fresh fruit or vegetable, tomatoes can be contaminated by bacteria from soil, water, and animal sources. Contamination from human sources may occur before, during, or after harvest, right up to the point of consumption. Bacteria on the tomato’s skin can be transferred to its internal flesh during cutting or slicing. Food poisoning outbreaks have occurred when poorly washed utensils or cutting boards (especially those used to handle raw meats) have been used to prepare fruits or vegetables. For this reason, it is important that you wash your hands with soap and water before and after preparing produce, and that you use clean equipment, utensils, and cutting surfaces.
Tomatoes should be washed before cutting. To wash, wet each tomato with water, rub its surface, rinse it with running water, and dry it with a paper towel. After washing, cut away the stem scar and surrounding area and discard it before slicing or chopping the tomato.
Washing tomatoes in a sink filled with water is not recommended since contaminated water can be absorbed through the fruit’s stem scar. The use of soap or detergent is neither recommended nor approved for washing fruits and vegetables because they can absorb detergent residues.
Cut or chopped tomatoes or products made from them, such as fresh salsa, should always be covered and refrigerated if they are not consumed within 2 hours of preparation. Cut or chopped tomatoes will last about 1 to 2 days if refrigerated.
METHODS FOR PRESERVING TOMATOES
Tomatoes are generally considered to be acidic, but their pH can vary significantly depending on their degree of ripeness and their variety. In general, the more ripe the tomato, the higher (less acidic) is the pH. The pH of whole, ripe tomatoes ranges from 4.3 to 4.9, putting some tomatoes in the low-acid range (defined as a pH greater than 4.6)
Tomatoes may be frozen whole, sliced, chopped, or puréed. Additionally, you can freeze them raw or cooked, as juice or sauce, or prepared in the recipe of your choice. Thawed raw tomatoes may be used in any cooked-tomato recipe. Do not try to substituted them for fresh tomatoes, however, since freezing causes their texture to become mushy. Tomatoes should be seasoned just before serving rather than before freezing; freezing may either strengthen or weaken seasonings such as garlic, onion, and herbs. Read more….
Dehydration removes water from tomatoes in order to preserve them. The amount of time it takes to dry tomatoes depends on the tomato variety, the air’s humidity during the drying process, the thickness of the tomato slices or pieces, and the efficiency of the dehydrator or oven.
The best tomatoes to dry are firm, ripe, and meaty. This type is usually oval shaped and called an Italian, Roma, plum, pear, or paste tomato. These varieties contain fewer seeds and more pulp and so produce dried tomatoes of better quality. Varieties such as beefsteaks that contain high levels of gel (called locular gel) surrounding the seeds are not recommended for drying. Read more…
One of the most popular methods of preserving tomatoes here is Southern California is by canning them, whether chopped, whole, made into salsa, marinara sauce or soup. Read more about the preparation and various methods of canning…..
Many useful resources are available to help you with variety selection and production of tomatoes:
- Home Garden Tomatoes: A Production Guide and Recommended Varieties for California, is available online at http://vric.ucdavis.edu/selectnewcrop.tomato.htm.
- At the same Web site, you can find ANR Publication 8116 with information on management of tomato pests, diseases, and disorders, such as blossom-end rot and fruit cracking.
- Key Points of Control and Management of MicrobialFood Safety: Edible Landscape Plants and Home Garden Produce (UC ANR Publication 8101, available free of charge at http://anrcatalog.ucdavis.edu), provides information on minimizing the contamination of fruits and vegetables in the home garden by organisms that cause foodborne illness.