A safe canning ketchup recipe is not a flavor sketch. It is a tested ratio of tomatoes, onion, vinegar, salt, and sugar that stays acidic enough for a boiling-water canner. The research-backed version from the National Center for Home Food Preservation (adapted from the USDA Complete Guide to Home Canning) uses 24 pounds of ripe tomatoes, 3 cups chopped onions, and 3 cups of 5% cider vinegar. It yields 6 to 7 pints and processes for 15 minutes at or below 1,000 feet.
That formula is the one to follow if the jars will sit on a pantry shelf. Homemade ketchup tastes brighter than supermarket bottles because you control the sweetness and spice. It also takes time: peeling, milling, and a long reduction are the real work, not the 15 minutes in the canner.
Why ketchup can go in a water-bath canner
Botulism risk belongs to low-acid foods (pH above 4.6). Plain vegetables, meat, and many tomato mixtures fall in that group and need a pressure canner. Ketchup is different because a tested recipe adds a large, measured amount of 5% vinegar. That acid, plus the tomatoes themselves, is what makes boiling-water processing acceptable.
The line is the recipe, not the word “ketchup.” A skillet sauce made from tomatoes, brown sugar, and a splash of vinegar may taste like ketchup and still be unsafe in a sealed jar. So can a family recipe that cuts the vinegar, doubles the onion, or adds extra peppers, celery, or beets. Those changes dilute acidity. Use a tested ketchup formula for shelf-stable jars. Refrigerate or freeze anything you invent.
The tested tomato ketchup recipe
This is the standard NCHFP tomato ketchup. Do not scale the tomatoes up without scaling the vinegar the same way, and do not treat blog “close enough” versions as equivalent.
Yield: 6 to 7 pints Pack: hot pack only Headspace: 1/8 inch Canner: boiling-water bath
Ingredients
- 24 pounds ripe tomatoes
- 3 cups chopped onions
- 3/4 teaspoon ground red pepper (cayenne)
- 3 cups cider vinegar (5% acidity)
- 4 teaspoons whole cloves
- 3 cinnamon sticks, crushed
- 1-1/2 teaspoons whole allspice
- 3 tablespoons celery seeds
- 1-1/2 cups sugar
- 1/4 cup canning or pickling salt
That tomato weight is roughly a half bushel. Paste types such as Roma, Amish Paste, or San Marzano cook down faster because they start with less water. Juicy slicing tomatoes work, but the pot will take longer to reduce and the yield can drop if you cook it extra hard to thicken.
What you can change and what you cannot
Home canning safety lives in a few ingredients. Flavor lives in the rest.
Do not change
- The vinegar amount, or use vinegar below 5% acidity
- Homemade vinegar, or vinegar of unknown strength
- A higher load of tomatoes, onions, or other fresh vegetables than the recipe lists
- Flour, cornstarch, ClearJel, or other thickeners (they slow heat penetration)
- Quart jars for this recipe (it is tested for pints)
- A shorter process time than the altitude table allows
Usually acceptable for flavor, not safety theater
- Dry spices: more cayenne, less clove, a pinch of garlic powder, mustard powder, or black pepper
- Salt type and amount, as long as you use a non-iodized canning, pickling, or kosher salt if you want a clear product
- Sugar amount for taste. Sugar is not the acid that makes this product water-bath safe. Cutting it changes flavor and body more than pH. If you want a no-sugar ketchup, treat that as a refrigerator or freezer project unless you are using another fully tested formula.
White vinegar at 5% can replace cider vinegar if you want a cleaner, less fruity tang. Keep the volume the same. A mix of the two is fine for flavor as long as every bottle is labeled 5%.
Equipment that actually matters
Use a stainless-steel or enamel pot. Aluminum and bare cast iron react with tomato acid and can leave a metallic taste.
A food mill or sieve is not optional if you want classic ketchup texture. Skins and seeds make the sauce bitter and grainy. An immersion blender can smooth the pulp after milling, but blending raw skins in is a poor substitute.
You also need:
- A 4-gallon (or similarly large) stockpot; 24 pounds of tomatoes take space before they collapse
- Cheesecloth or a spice bag
- Pint canning jars, new lids, and bands
- A boiling-water canner with a rack
- Funnel, bubble remover, and jar lifter
Half-pint jars are practical for a household that uses ketchup slowly. Process them for the same time as pints in this recipe. Do not invent a shorter time.
Step-by-step canning ketchup recipe
Read a basic water-bath primer before the first batch if you have never canned. The ketchup steps assume you already know how to load a canner and time a boil.
1. Prep the tomatoes
Wash firm, sound, ripe fruit. Skip moldy, rotten, or frost-killed tomatoes. Canning does not rescue spoiled produce.
Blanch in boiling water 30 to 60 seconds, until skins split. Move to cold water, slip off skins, and core. Quarter the tomatoes into the stockpot. Add the chopped onions and cayenne.
2. Cook, then rest
Bring the pot to a boil and simmer uncovered for 20 minutes. Cover, turn off the heat, and let it stand 20 minutes. That rest is in the tested procedure. Do not skip it to “save time.”
3. Infuse the vinegar
Tie cloves, crushed cinnamon, allspice, and celery seed in a spice bag. Add the bag to the vinegar in a small saucepan and bring it to a boil. Remove the bag. Pour the seasoned vinegar into the tomato mixture and boil about 30 minutes.
Infusing the vinegar instead of dumping ground spices into the pot keeps the ketchup from tasting dusty and makes milling easier.
4. Mill, then reduce
Run the hot mixture through a food mill or sieve. Return the smooth pulp to the pot. Add sugar and salt.
Boil gently, stirring often, until the volume is reduced by about half, or until the ketchup mounds on a spoon without a watery rim. This is the longest stage. It can take well over an hour depending on tomato type, pot width, and how hard you boil. A wider pot evaporates faster. Stir the bottom so it does not scorch.
Ketchup looks thinner when it is boiling than it will look cold. Judge it by the spoon test, not by whether it already looks like a commercial bottle.
5. Fill hot jars
Keep the ketchup hot. Fill hot pint jars, leaving 1/8-inch headspace. That is tighter than many sauce recipes. Remove air bubbles and add more ketchup if the level drops. Wipe rims, apply lids, and screw bands fingertip-tight.
6. Process in boiling water
Lower jars onto the canner rack. Water should cover the lids by at least 1 inch. Return to a full rolling boil, then start the timer.
| Style of pack | Jar size | 0–1,000 ft | 1,001–6,000 ft | Above 6,000 ft |
|---|---|---|---|---|
| Hot | Pints | 15 minutes | 20 minutes | 25 minutes |
When time is up, turn off the heat, remove the canner lid, and let the jars stand in the water for 5 minutes before lifting them out. Cool 12 to 24 hours. Check seals. Remove bands for storage. Refrigerate any jar that did not seal and use it first.
How to tell when homemade ketchup is thick enough
Watery ketchup is the most common disappointment, and it is almost always under-reduction, not a “failed recipe.”
Look for these signs:
- A spoonful holds a soft mound instead of running off like juice
- Liquid and solids do not immediately separate at the edge of the spoon
- The surface looks glossy, not watery
- Volume in the pot has dropped by roughly half from the milled stage
Paste tomatoes reach this point sooner. Slicing tomatoes can take much longer. If the pot is still thin after a long boil, keep going. Do not add starch to force thickness.
If you stop too early, you can still can a tested recipe that has the correct acid ratio, but the product will be more like a thin tomato sauce than ketchup. Quality suffers. Safety depends on the formula and process, not on how thick it looks.
Tomato choices that change the work, not the formula
Paste tomatoes: Best default. Less water, deeper color, shorter reduction.
Slicing tomatoes: Fine in a glut year. Budget extra stove time and expect more stirring.
Yellow or heirloom tomatoes: Color and flavor will not match red ketchup. Acidity still has to come from the tested vinegar load. Do not assume a low-acid yellow tomato is “safe enough” without that vinegar.
Green tomatoes: There are separate green-tomato ketchup formulas. Do not swap green fruit into the ripe-tomato recipe and call it the same product.
Starting from canned tomatoes or passata is not the NCHFP fresh-tomato procedure. If you want a shortcut, use a recipe that was written and tested for that starting material, or make a small refrigerator batch.
Two official ketchup variations
NCHFP also publishes Country Western ketchup (chile peppers, paprika, mustard, less sugar) and Blender ketchup (tomatoes plus sweet peppers and onions, blended instead of milled, with a much larger vinegar and sugar load). Both use the same pint process times as regular tomato ketchup. Choose one tested formula. Do not mix pieces of all three.
Blender ketchup is useful if you lack a food mill, but it is a different condiment: sweeter, sharper, and higher yield (about 9 pints). It is not a shortcut version of the 3-cup-vinegar recipe above.
Mistakes that ruin flavor or safety
Changing the acid math. Extra onion, extra pepper, or less vinegar is the most serious error. It can push a water-bath product out of the tested range.
Using the wrong pot. Reactive metal makes ketchup taste tinny.
Leaving seeds in. Bitterness is hard to fix later.
Scorching the reduction. Once the bottom burns, the whole pot tastes smoked in the wrong way. Moderate heat and frequent stirring matter more than blasting the burner.
Filling cool ketchup into jars. This is a hot-pack recipe. Cold product in a boiling canner risks jar breakage and under-processing.
Copying commercial headspace. Many websites say 1/4 inch or 1/2 inch. The tested ketchup headspace is 1/8 inch.
Skipping altitude. At 4,000 feet, 15 minutes is not the correct time.
Canning a “small experimental batch” with random ratios. Halving a tested recipe is reasonable if every ingredient is halved. Inventing a new ratio is not the same as making a half batch.
How long canned ketchup lasts
Store sealed jars in a cool, dark place, ideally 50–70°F. Use within a year for best flavor and color. The seal, not the calendar, is the first safety check: a bulging lid, leak, off odor, or spurting liquid means discard the jar without tasting.
After opening, refrigerate. Homemade ketchup does not have the same preservative package as a commercial bottle. Plan to use an open pint within a few weeks. That is why half-pints make sense for small households.
If you are ever unsure whether a tomato product was canned from a current tested recipe, USDA guidance for questionable home-canned tomato foods is to boil the food in a saucepan before eating: 10 minutes below 1,000 feet, plus 1 minute per additional 1,000 feet. That is a last-resort safety step, not a reason to can untested recipes.
If you only need a few cups
A 24-pound batch is a project. For a weeknight bottle, make a small pot from tomato paste or leftover sauce and keep it in the refrigerator. Do not water-bath a fridge recipe just because the big recipe is cannable.
Freezing is the right outlet for experiments: roasted tomatoes, smoked paprika, honey, less vinegar, added vegetables. Freeze in small containers with headspace. Thaw in the fridge.
FAQ
Can I can ketchup in quart jars? Not with this process. The tested recommendation is pints.
Can I use white vinegar? Yes, if it is 5% acidity and you keep the same volume.
Why is my ketchup thin after processing? It was thin going into the jar. Processing does not thicken it. Reduce longer next time. It will also set a little as it cools.
Can I leave the skins on if I blend well? You can eat that sauce from the fridge. For the tested canned product, mill or sieve as directed. Skins change texture and can leave flecks that never disappear.
Is homemade ketchup healthier? You can skip high-fructose corn syrup and decide how much sugar and salt go in. It is still a sweet-tart condiment. The health gain is ingredient control, not a free pass to use half a cup on fries.
Do I have to peel 24 pounds by hand? Blanching makes peeling faster. A food mill after a short cook can replace some peeling work, but follow the tested sequence: the official method peels first, then cooks, then mills after the vinegar boil.
Can I double the batch? Only if the pot can boil and reduce it evenly. Doubling every ingredient, including vinegar, keeps the ratio. A crowded, barely simmering pot gives you scorched bottom and thin top. Two sequential batches are often easier than one oversized pot.
A canning ketchup recipe is worth the afternoon when the garden is overflowing and you want a pantry condiment you can actually name the ingredients of. Use the tested proportions, reduce until the spoon test works, process for your altitude, and save the creative versions for the freezer.