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Growing  tomatoes

Preserving Tomatoes


Dr. Leonard Perry, Horticulture Professor
University of Vermont

Got tomatoes? Maybe you have too many tomatoes, and wonder how to possibly use them all. Consider making tomato sauce with excess ones from your garden, or buy a bulk box for this purpose from a local grower. Tomatoes and sauce can be canned, or easily frozen. Tomato slices are easily dried to a nice crispy texture. Small grape and cherry tomatoes can be roasted, then frozen. A little time invested in this fun harvest activity now will reward you with healthy and fresh snacks and meals for many months.

For making sauce, the right tools will make the job go quickly and easily and you’ll wonder how you can manage otherwise. Traditionally, you need to boil the tomatoes about a half minute, then soak briefly in cold water, so the skins slip off easily. Then mash them with a potato masher, and strain out seeds. Another method calls for cutting into quarters, bringing to a boil in a stainless steelpot, then crushing with a potato masher as you add more chunks and continue boiling.?????????????????

For about $25, you can get a stainless steel strainer with pestle to mash the tomatoes. For $50 to $100 you can get a food strainer with a handle. This is the kind I have and highly recommend. Even if you just use it a few times a year, as I do, it will save you countless hours. Simply cut the tomatoes into halves or large chunks, put them in the top funnel, then turn the crank. Out a chute comes the sauce, and the skins and seeds come out the tube.

Bring the raw sauce to a boil in a stainless steel pot, then simmer on medium heat, stirring frequently, to reduce the volume. Reduce by about one-third for a thin sauce, by about half for a thicker sauce. You then can freeze the sauce, or precook it with herbs and additions (such as garlic and onions) so it is ready to thaw and use later. If freezing, use containers made and labeled specially for this purpose. Leave a half inch or so of headspace for the liquid to expand as it freezes.

If you’re canning the sauce, don’t add oil as it potentially may lead to food sickness. For each pint of sauce, add one tablespoon of bottled lemon juice (or citric acid for canning, as per directions). Then ladle sauce into sterile jars, leaving about one-half inch of headspace. Finger-tighten lids, then boil jars (completely covered in water) in a pressure-canner for 35 minutes (for pint jars, 40 minutes for quarts). You also might consider canning whole or halved tomatoes.

If you have several types of tomatoes in your garden, this will make a rich and uniquely-flavored sauce each year. Figure on about two pints (one quart) of a thin sauce from each five pounds of tomatoes. A thicker sauce will, of course, require more tomatoes.

Other items to consider making are chili sauce, pickled tomatoes, salsa, and ketchup. Ketchup really is just a thick sauce, strained more finely as in a cheesecloth, and with ingredients such as garlic and seasoned vinegar. Vinegar also is a key ingredient for pickled tomatoes. Make sure to use the right proportion of ingredients from tested recipes. Salsa can be made to eat fresh and, to preserve its texture, is best canned. Salsa can be frozen but, when thawed, will be a bit watery for use with chips. Use this instead for cooking. More details on safe canning practices and recipes can be found from the National Center for Home Food Preservation (

Tomatoes dry well to a crisp, and easily. Begin by boiling and removing skins. Slice one-half inch thick. Soak for 10 minutes in a solution of one teaspoon citric acid per quart of water. Unlike most other vegetables, tomatoes don’t need blanching. Dry in a dehydrator, or in an oven at about 140 to 150 degrees for 6 to 24 hours, until crisp. If using an oven, you may need to prop the door open to make sure the temperature doesn’t get too high (monitor with an oven thermometer). You can stack trays with a couple inches space between them.

For roasting tomatoes, line a tray with parchment paper, then add small tomatoes that you’ve sliced in half lengthwise. Drizzle with olive oil, thyme, rosemary, ground black pepper, or coarse sea salt as desired. You may want to roast slices of garlic with them, or season with minced garlic or garlic powder. Roast at 350 degrees for 40 minutes, then caramelize for another 20 minutes at 400 degrees. You may be able to roast tomatoes while you have another dish in the oven cooking. Tomato skins slide off easily after baking, if you don’t want to eat them.

You can store roasted tomatoes in the refrigerator up to 5 days, and 5 months or more in the freezer. Serve as antipasto, on bruschetta, with a soft cheese such as mozarello and basil, add to tomato sauce, top on a pizza, or chop into a risotto. Roasting is a good way to use tomatoes that you may need to pick before they are fully ripe.

Distribution of this release is made possible by University of Vermont and New England Grows–a conference providing education for industry professionals and support for university outreach efforts in horticulture.

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