Turn Leftover Summer Tomatoes Into A Canned Sauce You Can Use All Year

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Summer is peak season for fresh tomatoes bursting with flavor. Tomatoes of varied, vivid hues line produce sections and farmers market stands, luring you in to stock up for all-purpose tomato sauces, tomato and herb soups, green bean and tomato panzanella salads, and more. But, to the attuned palate, tomatoes aren't quite as tasty during the fruit's off-season. Why not savor the plump sweetness of summer tomatoes all year by turning the leftover produce from your seasonal haul into a canned sauce? Skip canned tomatoes from the grocery store and invest in some basic canning staples, such as Ball wide-mouth Mason jars with lids and the Presto pressure canner.

To make your sauce, start by scoring the tomatoes with an "X" on the bottom. Cook them in boiling water for one to two minutes (until the peels come off easily), then transfer immediately to an ice bath to stop the cooking — overcooking tomatoes can lead to a mushy mess. Purée your tomatoes using a food processor for a slightly chunkier sauce, or an immersion blender for a smoother consistency. A food mill works well when puréeing seedless and skinless tomatoes. Once puréed, cook the tomatoes with other aromatics and seasonings for your sauce; beyond the basic garlic, onion, and herbs that provide the foundation for most tomato sauces, you can easily upgrade tomatoes with special ingredients or make a more robust tomato sauce with tomato leaves.

Canning tomatoes requires a bit of effort. Once you get the hang of it, making batches at home becomes second nature — and a fun way to discover the science underlying canned goods. Acidity is a key component to preserving tomato sauce because it protects the sauce from bacteria growth, including Clostridium botulinum, which causes botulism. Since tomatoes vary in acidity, make sure to add 1 tablespoon of bottled lemon juice per 16-ounce jar of tomato sauce. This lowers the pH, preventing bacteria and its spores from contaminating the sauce. It's essential to use bottled lemon juice over fresh because of the inconsistent pH levels of fresh lemons.

Heat and pressure also play pivotal roles in canning tomato sauce. For high-acidity sauces, water bath canning — submerging the jars in boiling water for a set amount of time — should suffice. The heat helps destroy microbes that can cause spoilage while also activating the jar's vacuum-sealing lid. Since this method doesn't reach temperatures high enough to kill bacteria, it's only safe for foods with naturally high acidity or added acidity. Pressure canning, on the other hand, reaches temperatures higher than boiling water, successfully destroying bacteria. This approach is suitable for low-acidity sauces — or if you'd rather bank on the added layer of safety from the low-pH and high-heat duo. When properly stored, canned tomato sauce holds up for about two years. However, the bright flavors deteriorate over time. For optimal flavor and enjoyment, use up the tomato sauce within a year.