There is no research-tested home-canning process for diced tomatoes. The USDA, the National Center for Home Food Preservation (NCHFP), Ball, and multiple university Extension services do not publish times or methods for packing small cubes into jars. Recipes that treat diced tomatoes like crushed or whole tomatoes are not validated.
That does not mean you have to give up pantry tomatoes. You can freeze diced tomatoes for a firm, grocery-store texture. You can can whole, halved, or crushed tomatoes using tested processes, then dice them when you cook. You can also use a tested crushed-tomato method that leaves plenty of chunks. What you should not do is pack raw or briefly heated cubes tightly into jars and assume a blog’s 35- or 45-minute water-bath time is enough.
The rest of this article explains why the “diced” process is missing, which methods are tested, and how to choose the option that matches how you cook.
Why Diced Tomatoes Are Treated Differently From Whole or Crushed
Home-canning safety depends on heat reaching the coldest spot in the jar long enough to destroy microorganisms that can survive in a sealed, oxygen-free container. Clostridium botulinum spores are the main concern. They do not grow in food at a pH of 4.6 or below, which is why acidified tomatoes can be processed in a boiling-water canner. Heat still has to move through the jar. Density, piece size, liquid, and how the food is packed all change how fast that happens.
Diced tomatoes pack tighter than whole or halved fruit. During processing, tomato cells collapse and the pack becomes even denser. Extra processing time that might compensate for that density would also turn the cubes to mush. Commercial plants can use faster heating, different cooling, and firming agents such as calcium chloride. Home kitchens cannot copy that process, so there is no approved home schedule for a firm-dice pack.
Crushed tomatoes are different because the tested method starts by heating and crushing a portion of the fruit to create juice, then adding larger pieces and boiling the mixture for five minutes before filling. That hot pack and the resulting liquid help heat move through the jar. Whole and halved tomatoes are packed with more space or with added water or juice, which also changes heat flow. Those packs were tested. A tight dice pack was not.
What You Can Safely Preserve Instead
Choose based on the texture you need later.
| Goal | Safest method | Texture after storage | Best uses |
|---|---|---|---|
| Firm cubes like a store can | Freeze diced tomatoes | Closest to commercial dice | Chili, salsa fresca, skillet dishes |
| Shelf-stable chunks | Can crushed tomatoes, hot pack, tested process | Soft, saucy chunks, not neat cubes | Soups, stews, sauces, casseroles |
| Shelf-stable pieces you dice later | Can whole or halved tomatoes | Soft whole/halves; dice after opening | Any cooked dish |
| Recipe that already includes diced tomatoes | Use only a tested salsa or mixed recipe as written | Follow that recipe’s texture | Only that tested product |
Freezing is the only home method that reliably keeps a true dice. Canning will always soften the fruit.
How to Freeze Diced Tomatoes
Freezing does not require added acid. Use ripe, sound fruit. Wash well. Peel if you dislike skins in cooked dishes; peeling is optional for the freezer. Core, trim bruises, and dice.
Pack into freezer containers or bags, leaving headspace for expansion. Include the juice that collects as you cut. That juice carries flavor and some of the tomato’s natural acid. Label and freeze. Quality holds about a year in an airtight container.
Thaw in the refrigerator and use in cooked dishes. Frozen dice release more liquid than canned commercial tomatoes, so drain or cook the liquid down when a recipe needs a thick result.
How to Can Chunky Tomatoes Using the Tested Crushed Method
If you want jars on the shelf, use NCHFP’s crushed tomatoes with no added liquid. The process starts with quarters, not tiny cubes. After heating, many pieces stay chunky enough for chili and soup. They will not look like supermarket diced tomatoes.
What you need
- Firm, ripe, preferably vine-ripened tomatoes. Do not can fruit from dead or frost-killed vines.
- Bottled lemon juice or food-grade citric acid. Do not use freshly squeezed lemon juice. Bottled juice has a standardized acidity; fresh juice does not.
- Optional canning salt for flavor only. Salt is not a safety ingredient.
- Pint or quart canning jars, new lids, rings, a boiling-water canner or a pressure canner, and a jar lifter.
Quantity guide from NCHFP: about 22 pounds of tomatoes fill 7 quarts; about 14 pounds fill 9 pints. Plan on roughly 2¾ pounds per quart. Paste types such as Roma or San Marzano give a thicker pack with less watery juice than large slicing tomatoes.
Acid amounts for every jar
Add acid to each jar before or after filling. Do not reduce these amounts. USDA still recommends acidifying these tomato products even when you use a pressure canner, because the published pressure times were developed with acidified tomatoes.
- Pint: 1 tablespoon bottled lemon juice or ¼ teaspoon citric acid
- Quart: 2 tablespoons bottled lemon juice or ½ teaspoon citric acid
Five-percent vinegar can be used (2 tablespoons per pint, 4 tablespoons per quart), but it changes flavor more than lemon juice or citric acid. Sugar may be added later to soften the taste. Do not cut the acid to make the product milder.
Do not add onions, peppers, garlic, meat, or thickeners to this product. Those change acidity and density. Use a tested salsa, sauce, or soup recipe if you want mixed ingredients.
Step-by-step (hot pack, crushed)
- Wash jars. Keep them hot. Prepare lids according to the manufacturer.
- Wash tomatoes. Dip in boiling water 30 to 60 seconds, until skins split. Cool in cold water, slip off skins, and remove cores. Trim any bruised or discolored flesh. Cut into quarters.
- Heat about one-sixth of the quarters in a large pot, crushing them as they go in so they release juice. Stir so they do not scorch.
- When that portion boils, add the remaining quarters gradually, stirring constantly. Those pieces do not need to be crushed; they soften as they heat.
- After all tomatoes are in the pot, boil gently for 5 minutes.
- Add the measured acid (and optional salt) to each hot jar.
- Fill immediately with the hot tomatoes, leaving ½-inch headspace. Remove air bubbles and adjust headspace if needed.
- Wipe rims, apply lids, and tighten rings fingertip-tight.
- Process in a boiling-water canner or a pressure canner using the times below for your altitude. Start timing only after the water returns to a full boil, or after the canner reaches the required pressure.
Boiling-water canner times for crushed tomatoes
| Jar size | 0–1,000 ft | 1,001–3,000 ft | 3,001–6,000 ft | Above 6,000 ft |
|---|---|---|---|---|
| Pints | 35 minutes | 40 minutes | 45 minutes | 50 minutes |
| Quarts | 45 minutes | 50 minutes | 55 minutes | 60 minutes |
These times are for the hot-pack crushed product with no added liquid. They are not a license to pack raw dice and use the same clock.
Pressure-canner options for the same crushed product
Acidify the jars the same way. NCHFP lists more than one pressure combination. Common choices:
Weighted-gauge canner, pints or quarts: 20 minutes at 5 lb (0–1,000 ft) or 10 lb (above 1,000 ft). Other listed combinations include 15 minutes at 10 lb.
Dial-gauge canner, pints or quarts: 20 minutes at 6 lb (0–2,000 ft), then increase pounds as altitude rises (7 lb at 2,001–4,000 ft, 8 lb at 4,001–6,000 ft, 9 lb at 6,001–8,000 ft). A 15-minute process at 11 lb (0–2,000 ft), with higher pressure at higher elevations, is also listed.
Use the chart in the current NCHFP crushed-tomato directions for your exact gauge and altitude. Do not invent a shorter time because the pieces look small.
After processing
Let the canner sit 5 minutes after the process ends before removing jars. That pause reduces siphoning (liquid loss). Cool jars 12 to 24 hours, undisturbed. Check seals, remove rings for storage, wipe jars, and label.
Unsealed jars can be refrigerated and used soon, frozen, or reprocessed within 24 hours in a clean jar with a new lid. If a sealed jar later bulges, leaks, spurts, smells off, or looks moldy, do not taste it. Discard it safely.
Separation—tomato solids floating over a layer of juice—is common and not a safety defect by itself if the product was prepared and processed by a tested method. Use jars with more exposed solids first if the color bothers you.
Canning Whole or Halved Tomatoes, Then Dicing at the Stove
If you want pieces you can cut to size later, use a tested whole-or-halved process. Options include packing in water, packing in tomato juice, or raw-packing with no added liquid. Each option has its own process time. The no-added-liquid raw pack, for example, is much longer in a water bath (85 minutes for pints or quarts at 0–1,000 ft) than crushed tomatoes, because heat moves differently through that pack.
Acidify every jar at the same rates listed above. Peel as directed in the tested recipe. When you open a jar, drain or use the liquid and dice the tomatoes for chili, soup, or sauce.
This route avoids the density problem of a pre-diced pack and still gives you shelf-stable fruit.
What Not to Do
These habits show up often in blog posts and forums. They are the usual reasons a “diced tomato” batch is unsafe or poor quality.
- Do not treat an untested diced recipe as equivalent to crushed or whole tomatoes. Piece size and pack density change heat penetration. Extension specialists have said you cannot safely borrow the whole-tomato times for a dice pack.
- Do not skip acid. Modern tomato varieties and growing conditions can produce fruit with a pH above 4.6. Added bottled lemon juice or citric acid is the control that makes water-bath processing appropriate for these products.
- Do not use fresh lemon juice, aspirin, or ascorbic acid as the canning acid. Those are not the tested acidulants.
- Do not add extra vegetables to a plain-tomato jar. That product becomes a different food and needs a tested mixed recipe, often with a pressure canner.
- Do not can tomatoes from frost-killed vines.
- Do not thicken with flour, cornstarch, or cream before canning.
- Do not drain off tomato juice and then can the solids with only the added lemon juice. The fruit’s own liquid is part of the tested product. Draining and squeezing, especially after freezing and thawing, can change acidity and density.
- Do not assume a sealed lid means the food is safe. A seal only means the lid vacuumed down. Safety comes from the tested process.
Why Store-Bought Diced Tomatoes Look Different
Commercial diced tomatoes are packed with firming agents and processed on equipment that heats and cools faster than a home canner. That is why the cubes stay neat. Home-canned crushed tomatoes will be softer. Home-frozen dice will be closer to the commercial look after thawing, with more weeping liquid.
If a recipe depends on distinct cubes that hold shape in a salad or a barely cooked salsa, freeze. If the tomatoes will simmer, canned crushed or home-canned halves work well.
Common Problems After You Open or Cool the Jars
Liquid loss (siphoning). Often caused by packing too full, skipping the bubble-release step, or cooling the canner too fast. If the jar sealed and a reasonable amount of liquid remains, the food can be stored; use jars with more exposed fruit first. If most of the liquid is gone, refrigerate and use soon.
Floating tomatoes. Normal. Solids rise as air leaves the tissue.
Soft, broken pieces. Expected with any home-canned tomato product. Longer heat means softer texture. That is one reason a true dice process was never published: the time needed for safety would destroy the cubes.
White or pale areas on fruit above the liquid line. Usually cosmetic oxidation, not spoilage, if the seal and process were correct.
Forgot the lemon juice. Do not guess. The safe options are to refrigerate and use the food promptly, freeze it, or discard it. Reprocessing only helps if you can still follow a complete tested procedure, including acid, in time.
Frequently Asked Questions
Can I water-bath can diced tomatoes if I add lemon juice? Acid is required for tested tomato products, but acid alone does not make an untested pack safe. Heat still has to reach the center of that specific pack. There is no tested time for a diced pack.
Can I pressure-can diced tomatoes and skip the lemon juice? Not with a published home process. For crushed, whole, and juiced tomatoes, USDA still calls for acidification even when a pressure canner is used, because those pressure times were built around acidified tomatoes. There is still no tested diced-tomato pressure schedule.
Do I have to peel tomatoes? Tested crushed and whole/halved directions start with peeled fruit. Skins can roll into tough bits and were part of how those procedures were developed. For freezing, peeling is a quality choice.
Are skins a safety issue? The larger issue is following the tested preparation. If you want skins on, freezing is the simpler safe option.
Can I can tomatoes I previously froze? You can use previously frozen tomatoes in tested sauce or crushed-style products if you keep the thawed liquid and follow a current tested process. Frozen fruit collapses, so it is a poor candidate for anything meant to stay in cubes. Do not can fruit that froze on the vine.
Is it safe to can diced tomatoes inside a tested salsa recipe? Yes, when you follow that salsa recipe exactly, including the stated amounts of acid and the stated process. You cannot lift the dice from a salsa recipe and can them alone with salsa times.
Which acid tastes least like lemon? Citric acid is usually more neutral than bottled lemon juice. Vinegar is the most noticeable.
How long do home-canned tomatoes keep? Use within a year for best quality. Store in a cool, dark, dry place with rings off. Quality drops faster in a hot garage.
A Practical Decision Rule
If you opened this article because you have a pile of ripe tomatoes and a mental picture of neat cubes in jars, freeze the dice. If you want shelf-stable tomatoes for winter cooking, can crushed tomatoes by the NCHFP hot-pack method, or can whole or halved tomatoes and cut them when you cook.
The blogs that skip this distinction are easier to follow for an afternoon. They are not a substitute for a tested process. For current charts and procedures, use the National Center for Home Food Preservation tomato pages and your state Extension service, and adjust every process for your altitude.