Tomatoes rank as one of the most popular items to can. Whether whole, in salsas or other sauces, or even in jams, they are a treat. Tomatoes plucked straight off the vine, still warm from the sun — there is nothing better. It’s worth waiting for the season to come around, but if you can’t, here are some ideas for making sure your harvest will take you (at least part of the way) through the calendar.
Q: Help! Tomato overload! What is the quickest way to put ’em up?
A: My favorite way to preserve tomatoes is to cold pack whole fruit, but I don’t always have the time — or the patience — for the peeling and coring required. I use the recipe for Avalanche Sauce when I have just that — more tomatoes than time. It’s also useful when I want to process a wide variety of tomatoes. While the meaty texture of paste tomatoes makes them the best choice for cold packing, this recipe can accommodate any variety you have on hand.
Q: Do I have to use plum tomatoes in my recipes?
A: Plum tomatoes are the tomato of choice in many recipes. They are meaty and have relatively fewer seeds when compared to globe varieties. Globe tomatoes tend to be a bit more watery than plums, so they aren’t the best choice for all recipes. You can use globe tomatoes if that is the variety you have on hand, but your recipe may have a subtler tomato flavor and be a bit looser than if you had used plum varieties.
Q: Do I have to skin tomatoes before processing them?
A: Skinning tomatoes is time-consuming, it’s true, but most often it’s a necessary part of the process. The heat of processing will separate the skins from the fruit anyway and leave you with big pieces of tough stuff floating around in your recipe, so better to get it out of the way before you pack your jars. The only exception? You can skip the skinning, if you like, in recipes where you chop your tomatoes into small pieces, such as in salsas. Some might argue that the skins may impart a slightly bitter note to your recipe, but I’ve not found that to be the case. And if the skin bits are tiny enough, I don’t even notice them.
Q: My recipe calls for cilantro, but this herb tastes like soap to me. Are there any substitutes?
A: No herb divides a crowd like cilantro. Some people love it and others can’t stand it. Cilantro is an allergen for many eaters — their reaction makes the herb taste like soap — so detractors may actually be allergic to the greenery, not just picky.
You can substitute basil or parsley for cilantro, if you like. The swap will alter the flavor of the dish, but perhaps in a way that you prefer. Alternatively, you can leave out the herbs altogether. Your recipe will still taste great.
Q: Why are my canned tomatoes floating to the top of the jars?
A: You’ve got a case of fruit float. It is pretty common but no less distressing. Fruit float is caused by air that remains within the cell walls of the produce after processing. It happens most commonly to fruits that are canned whole or in preparations, such as quick jams, that do not cook for very long. Often, tomatoes will release this trapped air into the headspace of the sealed jar and the fruit will redistribute throughout the liquid over time. So give jars of whole tomatoes a few weeks on the shelf and they may very well turn from what looks like a failed science experiment into the gorgeous home-canned tomatoes of your dreams all on their own.
Q: I have some tomatoes that are a little past their prime. Can I still preserve them?
A: Tomatoes are available for such a short time each year; it seems a shame to waste a bite. Canning — either with the boiling-water method or by pressure — is recommended for tomatoes that are well ripened, though they should still be firm and nicely colored throughout. This level of ripeness ensures that they have a good pH level — essential to successful storage. And such tomatoes will keep their shape best if you can them whole.
Overripe tomatoes can be soft and will lose some of their acid as they age, making them less than ideal for canning. Any spots of mold or damage may also have increased their bacterial load beyond the carrying capacity of the canning process — a small bit of mold on the surface means that tendrils of contamination may reach down into the fruit. However, if you can trim away any damage, you can safely freeze them. While freezing will not improve the quality of the fruit, it will stop time. And while it will not eradicate contaminants, it will render mold and fungal spores inactive so they cannot do any additional damage.
To freeze the tomatoes, blanch and remove their skins or cook down into a sauce or paste and pack into airtight containers. You needn’t add citric acid or lemon juice for frozen tomatoes. They will keep in the freezer for up to 6 months.
If the tomatoes are badly rotted, their only use is in the compost bin.
Q: Why do cold-packed tomatoes need to be processed for so long?
A: The density of the fruit, the size of the jar, and the starting temperature of the recipe being ladled into the jar all factor into the final processing time for any product. For cold-packed tomatoes, this adds up to a processing time of well over an hour for quarts (85 minutes, to be precise). Don’t cheat! It takes the heat that long to penetrate all the way to the center of the jar. Any less time and you will have an unprocessed core of food in the middle of each jar, which can lead to poor, if not dangerous, results. If you don’t have the patience for the extended processing, cook your tomatoes first. Quarts of crushed, cooked tomatoes process in 45 minutes, nearly half the time.
Q: There are little black spots on the lids of my tomato jars. Is this safe?
A: I can’t tell you how many jars of tomatoes I threw out thinking that those little spots on the lid were signs of spoilage. Such a waste. Little black spots on the underside of the lid of canned tomatoes are mineral deposits — they are perfectly normal and harmless. However, black spots on the top of or within the food are not okay — that is a sign of spoilage and the contents should be discarded immediately.
Q: Which variety of tomato is best for canning?
A: Different varieties of tomatoes are intended for different uses. You will get the best results if you choose the tomato best suited for your purpose.
Q: Are heirloom tomatoes safe to can?
A: Not only are they safe to can, but heirloom tomatoes are also delicious to can! Grown for their flavor rather than their ability to withstand commercial harvesting, heirloom tomatoes pack a lot of great taste. Some varieties of heirloom tomatoes are described as “low acid,” which gives the impression that they may not be suitable for the canning process, but that is not the case. All tomatoes can be canned using the boiling-water method; you just have to follow your recipe.
Keep in mind that tomatoes destined for processing — by either the boiling-water method or the pressure canner — must be treated to a little boost of acid in the form of lemon juice or citric acid powder. Why? The extra acid guarantees the low pH that is necessary for safe processing using the boiling-water method, and it keeps processing times short and sweet when using a pressure canner. Whether you are canning heirloom or commercial varieties, don’t leave it out!
Q: I love to put lots of vegetables in my spaghetti sauce — mushrooms, peppers, onions, and even a little eggplant sometimes. Can I still can it?
A: The answer is yes and no. You can can it, but since you added a lot of nonacidic ingredients to your sauce, you have to use a pressure canner. Incidentally, you have just described one of the most common mistakes that new canners make: using the boiling-water method for nonacidic recipes. While tomatoes are acidic and can be processed without pressure, adding vegetables, as you have described for this sauce, will alter the pH to a point that it is no longer suitable for the boiling-water method. Always follow your recipe. Never alter the quantity of vegetables called for or lower the amount of acid or acidic ingredients indicated; doing so could create an unstable product that can sicken you or worse. Ditto with salsas. Never add extra onions, peppers — or heaven forbid, beans — to the pot if they are not called for in your recipe.
Q: I have a great recipe for marinara sauce. Can I can it?
A: It depends. Did you get your recipe from a canning book? If you did, great, go right ahead and can it. If you didn’t, then I would suggest you freeze your wonderful sauce rather than trying to get it shelf stable. For one thing, homemade marinara sauce often includes a fair amount of onions, garlic, and other produce that will throw off the acidic pH you need for shelf-safe products canned with the boiling-water method. Pressure canning is the preferred method for nonacidic recipes, but the timing and pressure necessary to get consistent results are impossible to determine without further testing. Stay safe: only can recipes from reliable sources.
Q: Do I have to put salt in my canned tomatoes?
A: Salt is frequently listed as a recommended ingredient in tomato recipes, but it is included strictly for flavor alone. The proportion of 1⁄2 teaspoon per pint jar and 1 teaspoon per quart jar will flavor your tomatoes without making them taste salty. You can add the salt to the top or bottom of the jar — it makes no difference — and the convection action of the heat through the jars will distribute it throughout. You can use less, if you prefer, or you can eliminate the salt altogether if you like.
Q: I made a ton of salsa. Can I use it on anything but tortilla chips?
A: You bet! Salsa is great on grilled chicken or fish. You can also blend it with some sour cream or softened cream cheese for a quick, tangy dip. Toss it with pasta for a zesty side dish. Or use it instead of sour cream and butter to top a baked potato.
Q: I like fresh salsa. Do I have to cook it before I can it?
A: Fresh salsa is a treat, but all recipes that are canned — whether via the boiling-water method or pressure canning — become cooked during the process. Both methods use heat to destroy any contaminating bacteria that might be lingering in the food and deactivate the enzymes that could lead to decay. So it is not possible to have fresh, canned salsa.
Q: Should I use the boiling-water method or a pressure canner to can my tomatoes?
A: You can use either the boiling-water method or a pressure canner to process your tomatoes. The preparation for both is the same, including acidification. For pints, use 1 tablespoon bottled lemon juice or 1⁄4 teaspoon citric acid; double that for quarts. The boiling-water method is the easiest, but a pressure canner has a greatly reduced processing time. It’s really a matter of choice and available equipment.
Q: Why are tomatoes seeds sprouting in my jars?
A: Germinating seeds in a canning container are an indication of spoilage. Sprouting tomato seeds are a sign that something has gone wrong, and the product should be destroyed. Possible causes include:
Insufficient processing. Tomatoes that have been processed fully will not have the enzymatic action sufficient to sprout. Always process your tomatoes for the full amount of time indicated in your recipe. If you are using the boiling-water method, be certain that during that time the water level was never less than 2 inches above the jars. If you are pressure canning, be sure that the pressure never dips lower than indicated in your recipe.
Hot storage. The cans of tomatoes may have been stored in a warm area that encouraged sprouting. Always store your jars in as dark and cool a place as possible to discourage activity within the jars.
Q: I like lime juice in my salsa. Can I use that instead of vinegar?
A: Lime juice is commonly added to fresh salsas to give them a citrus kick. You can sometimes find canning recipes that use citrus juices as an acidifying agent as well. If that’s the case, you can certainly follow such a recipe, as long as it comes from a reliable source. Never substitute lime juice for vinegar in a recipe that doesn’t call for it. Canning recipes are precisely calibrated for safe results, and you need to use the quantity and kind of acid indicated to achieve a wholesome product.
Q: I like my salsas nice and thick. Can I use thickeners to give them the texture I like?
A: Canned salsas have a thinner consistency than commercial brands. The extra moisture in homemade products allows the heat to penetrate to the center of the jar more easily during processing and ensures that the contents of the jar are submerged under an acidic brine during storage.
Never try to thicken your canned salsa by cooking it down or adding thickeners to the recipe. Doing so will throw off your processing time and will expose the top of your jarred ingredients during storage.
If you want a salsa that is a little thicker, drain off some of the liquid before serving. You can reserve the drained liquid and add it to soups and stews or stir it into your next Bloody Mary for a spicy kick.
Q: I like my salsa extra spicy. Can I just double the amount of chiles called for in the recipe?
A: You should never increase the amount of any produce ingredient in your recipe. Doing so will throw off the important acid balance that keeps your canned foods safe on the shelf and will invite contamination. You can, however, swap in hotter peppers to crank up the heat a bit. If your salsa calls for jalapeños, for example, you can substitute an equal amount of hotter chiles such as habaneros. You’ll get the heat you seek without risking your results.
Q: Most salsas are just too spicy for me. What can I do to temper the heat when I make them?
A: One of the benefits of preserving your own food at home is that you can control the taste. If your salsa is too spicy, you can turn it down by substituting sweet peppers for a portion of the chiles called for in the recipe as long as the total weight of chiles and peppers is consistent with the recipe. For example, a salsa recipe that calls for 1 pound of chiles can be modified for milder results by using 1⁄2 pound of chiles and 1⁄2 pound of sweet bell peppers instead. Never alter the total volume of peppers in the recipe or you will throw off the acid balance necessary to keep your food safe on the shelf.
Q: What are Scoville units?
A: Scoville units measure the amount of capsaicin, the spicy compound found in foods such as chiles and peppercorns. The more capsaicin, the higher the number of Scoville units and the spicier the food. Jalapeño peppers, for example, are relatively mild, with a Scoville rating under 8,000 units, while the legendary ghost pepper checks in with a whopping 1,000,000 Scoville units. Hot stuff, indeed.
Q: My salsa verde recipe calls for tomatillos. What are they?
A: Tomatillos look like green tomatoes but are covered in a thin, papery husk that must be removed before they can be used in a recipe. Tomatillos have a tart flavor and need to be cooked to be enjoyed.
Q: I just cooked up a batch of salsa and it tastes so intense. What gives?
A: The flavor of canned salsas mellows over time. Right out of the pot, the vinegar might seem overwhelming and the spice level might be too strong, but give the salsa a few weeks in the jar and it will taste just right. Keep in mind, also, that hot food reveals more of its flavor than chilled bites. A spoonful of hot salsa will taste like a different recipe after it has cooled. Trust your recipe and try the salsa again after it has been processed and spent 3 to 4 weeks on the shelf.
Q: Can I put black beans in my salsa?
A: Even recipes that seem acidic, such as tomato sauces and salsas, do not always achieve the proper pH level necessary to be safely canned using the boiling-water method. A basic tomato sauce, for example, is a recipe that is commonly and correctly listed as safe for the boiling-water method, but the minute that recipe is altered in any way — by adding extra onions or other vegetables such as peppers or mushrooms or by adding meat to the sauce, it becomes a nonacidic recipe and must be pressure canned. The same goes for salsa. You will find many salsa recipes that are appropriate for the boiling-water method. But add extra ingredients — more peppers or a double dose of onions, or, worst of all, load it up with black beans or corn — and you will have certainly altered the pH too much for them to be canned safely with the boiling-water method.
Makes about 3 quarts canned as juice, about 11⁄2 quarts when reduced to a thick sauce
I use this recipe when the tomatoes are coming in quicker than I can cold pack them or when I am lucky enough to have surplus globe tomatoes on hand — the round kind that are great in recipes, but not suitable for canning whole. I can easily cook 20 to 30 pounds at a time. Now that’s a workhorse of a recipe! You’ll need a food mill to process the tomatoes.
Can: Use the boiling-water method. Add 1 tablespoon lemon juice to each pint jar and 2 tablespoons to each quart jar to be filled. Ladle the sauce into the clean, hot jars along with the lemon juice, leaving 1 inch of headspace between the top of the sauce and the lid. Use a bubble tool, or other nonmetallic implement, to release trapped air by running it along the inside of the glass. Wipe the rims, cover the jars, and screw the bands on just fingertip-tight. Process for 35 minutes for pints and 40 minutes for quarts. Turn off the heat, remove the canner lid, and let the jars rest in the water for 5 minutes. Remove the jars and set aside for 24 hours. Check seals, then store in a cool, dark place for up to 1 year.