Plum tomatoes, otherwise called Italian or paste tomatoes, are best for preserving because they are meaty and have less juicy seed pulp. But any tomato type—even huge slicers or tiny cherry tomatoes—can be used; you’ll just need more to start with to compensate for the extra juiciness. Ripe tomatoes are best for crushed tomatoes and sauce; overripe tomatoes make the best paste. A pound and a half of tomatoes will make about a pint of crushed tomatoes, about ½ pint of sauce (depending on how thick you make the finished product), or a few ounces of paste (also depending on how thick you make it). These basic tomato products can be frozen, or preserved using a hot-water-bath canner or a pressure canner. For variety, you may also want to make some oven-dried tomatoes.
Basic Crushed Tomatoes
Bottled lemon juice or vinegar
Freezer containers (I use wide-mouth can-and-freeze pints) or canning jars with bands and new lids
Follow these instructions if you will be canning your crushed tomatoes. Before proceeding, put the hot-water bath on to heat and put the clean jars and lids in hot water to warm up. Or freeze them if you're not going to be using them in the near future.
First, wash and skin your tomatoes. Skinning is easy: Bring a medium pot of water to a boil, and use a slotted spoon to carefully lower the tomatoes, a few at a time, into the boiling water. Fish them out after about 30 seconds to a minute (if you blow on one and the skin splits and curls back it’s ready), and put them in a large bowl of cold water. The quick dunk in boiling water cooks the flesh just under the skin, allowing you to slip it off cleanly with your fingers after the tomatoes cool (this works for peaches too). Place the skinned tomatoes into a colander and repeat for all tomatoes.
Next, seed them. (You can choose to leave the seeds in, but I prefer to remove them.) Use a sharp knife to cut out any core or solid areas, and then cut each tomato in half around its middle so that you are cutting through all the cavities full of seeds. Hold a cut half in your palm, cut side away from your palm, and squeeze the seeds and jelly around them out into a container (you can save the juice for cooking, but I usually send it all to the compost heap). If you want to get every seed, use your finger to sweep each cavity.
Drop the squeezed halves into a large non-reactive pot and heat, using a potato masher to crush them enough so a little juice collects in the bottom. Bring the crushed tomatoes to a simmer, stirring frequently to prevent sticking or scorching, for 5 minutes, then turn off the heat. Your tomatoes should still be a bit chunky, depending on the variety of tomatoes you used. But otherwise, they're ready to pack up.
If you're freezing, allow the tomatoes to cool until they are still hot but won’t burn you, ladle into freezer-appropriate containers (leaving space at the top for expansion) and label. If canning, fill your hot, sterilized jars immediately, adding 1 tablespoon of juice or vinegar to each pint to ensure the acid level is high enough for safety, and process as recommended by the National Center for Home Food Preservation (NCHFP).
Plain Tomato, Pizza, and Pasta Sauces
Converting crushed tomatoes into tomato or pizza sauces either now or later in the year is as simple as cooking the tomatoes down a bit longer until the result is as thick as you want it. You can add seasonings, such as herbs or garlic, during the cooking, but I prefer to leave mine plain and season it when I’m cooking later. As with crushed tomatoes, you can freeze the sauce as soon as it cools a little, or can it using the appropriate processing times.
I prefer to make mostly plain sauce in the summer and add seasonings, veggies, and meat when I’m preparing the actual dish, but it is easy and safe to make finished sauce and freeze it if you have veggies you’d like to use up. Canning spaghetti sauce with lots of veggies and/or meat is more complicated than canning plain or lightly seasoned tomato sauce, as the product must be pressure-canned and processed for as long as would be required for the most demanding ingredient to make the final product safe to store. If you want to try canning meat- or veggie-filled sauces, be sure to consult the NCHFP's advice and not exceed the amount of veggies or meat called for in your recipe.
Another kitchen staple you probably find yourself reaching for during the winter is tomato paste. You can use it to thicken your crushed tomatoes or use it as an added flavoring in other things, but like crushed tomatoes, it usually comes in cans or tubes lined with BPA.
To make it, just continue cooking your crushed tomatoes down until they turn into paste (this may take an hour or more). I like to add a finely diced sweet red pepper during the final cooking to add extra sweetness and flavor. The only tricky part is, as it gets thicker, your paste becomes easier and easier to scorch, and it starts spitting and making a mess. Once the crushed tomatoes start to reach a thick, saucelike consistency, you can avoid that scorching and spitting by pouring the sauce onto a large, rimmed, non-reactive baking sheet or into a glass baking dish. Bake it in a 300ºF oven to finish the thickening process. Every half hour or so, use a silicone spatula to scrape the thickened areas into the center, stir, and spread the paste back out over the pan. Once it gets really thick, you can turn the oven down even further. Your paste is done when it gets very thick and shiny.
Paste can be frozen in small quantities, either in ice cube trays or just as dabs on a cookie sheet covered with a baking mat or wax paper, and stored in an airtight container in the freezer. Paste is so concentrated that you can store it safely in the refrigerator for many months by packing it firmly into small sterilized glass jars and covering the surface with a layer of olive oil. Whenever you scoop some out, use a clean spoon, press down and level the remaining paste, and add a little more oil to cover it as needed. If you are short on freezer or fridge space, you can even turn tomato paste into tomato leather, which is made the same way as fruit leather (tomato paste is too thick for safe boiling-water-bath canning). Store the finished leather at room temperature in a glass jar with a tight lid. When you need some for cooking, tear the tomato leather into small bits and soak them in a little hot water to turn back into paste.
Roasted Tomato Paste
For an easier tomato paste recipe, try this method. It bypasses all the cooking down and stirring and adds a delicious extra layer of flavor.
1½ pounds tomatoes (overripe ones are best)
2 garlic cloves
1 red pepper, chopped
Cut the tomatoes in half, trimming out any cores or hard areas, squeeze out the seeds, and place the halves, cut side up, on a large, rimmed, non-reactive baking sheet or glass baking dish (no need to peel the tomatoes). Add the peeled garlic and/or seeded chunks of red pepper. Drizzle everything with a little olive oil. Bake at 300ºF for an hour to an hour and a half, until the tomatoes are somewhat shrunken and browned, and still moist but not crispy. Use a food processor, immersion blender, or mortar and pestle to puree everything into a smooth paste (if it isn’t as thick as you'd like it, return the paste to the oven as for cooked-down paste). Freeze or store in the fridge as above.
Farm gal, library worker, and all-around money-pincher Jean Nick shares advice for green thrifty living every Thursday on Rodale.com.
For more food preservation tips from the Nickel Pincher, see:
• Preserve Summer's Tastiest Harvest to Enjoy in Winter!
• Turn Summer Fruit into Preserves and Jellies
• Easy Refrigerator Pickles, No Canning Needed