How to Can Tomato Paste in Canada (Bernardin Method)
To safely can tomato paste in Canada, put 1 1/2 tsp (7.4 mL) of bottled lemon juice into each hot 250 mL jar before you fill it, then process 45 minutes in a boiling water bath at up to 305 m, adding time above that band. Those are Bernardin's tested figures. Paste is dense, so heat penetrates slowly — the small jar and the long time are what keep it safe; do not size up to 1 L jars, which Bernardin does not publish for paste. Cook sieved tomatoes down for a few hours until spreadably thick, fill to 1 cm headspace, and cool 24 hours. The easiest alternative is to skip canning and freeze the paste in tablespoon portions.
Tomato paste is the most concentrated thing you can make from a tomato — and the most divisive to can. Some Canadian preservers love a shelf full of little jars; plenty of others decide, halfway through the third hour of stirring, that they’ll just freeze it next time. Both camps are right. This guide covers the water-bath method following Bernardin, and the freezer shortcut, so you can pick (growing tomatoes in Canada).
The acidifier amount, jar size and processing time below are Bernardin’s published figures for tomato paste.
Corrected 30 Aug 2026: this page previously said Bernardin uses a 125 mL jar and hedged the processing time to “whatever your edition lists”. Bernardin publishes a 250 mL jar and 45 minutes at up to 305 m, with 1 1/2 tsp (7.4 mL) bottled lemon juice per jar. Note the direction of the acid error: the old page’s “about 1 tsp per 125 mL jar” works out to 2 tsp per 250 mL, which is more acid per unit volume than Bernardin calls for, not less — a reader who followed it over-acidified. The jar size was the real defect, because a 250 mL process time applied to the jar we named would have been the wrong pairing.
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Two safety points, not one
Every tomato recipe needs acidifying, and paste is no exception:
Add 1 1/2 tsp (7.4 mL) bottled lemon juice to every 250 mL jar, before you fill it.
But paste adds a second wrinkle the thinner tomato products don’t have: it’s dense, so heat travels through it slowly. Bernardin’s tested paste recipe handles this by using a small jar (250 mL) and a long process — 45 minutes. Both matter. For comparison, Bernardin gives crushed tomatoes the same 45 minutes in a 1 L jar; paste needs that full time in a jar a quarter the size, which is how much slower the heat moves through it.
- Don’t size up to 500 mL or 1 L jars — Bernardin publishes no time for paste in them, and the centre may not reach a safe temperature.
- Don’t shorten the 45 minutes to save the stove.
If either of those makes you nervous, that’s a fair instinct — jump to the freezer method below, which sidesteps both.
What you need
- About 5.5 kg (12 lb) ripe paste tomatoes — Roma or San Marzano; you’ll get only 2–3 × 250 mL jars from this, because paste is mostly evaporated water
- A food mill or fine sieve, and a wide, heavy-bottomed pot (thin pots scorch)
- 250 mL Bernardin jars with new SNAP lids
- Bottled lemon juice OR food-grade citric acid
- Standard canning kit — jar lifter, headspace tool, funnel, water-bath canner, ladle (which canner to buy)
Sieves the skins and seeds out for a smooth paste, no peeling. Three discs also handle applesauce and berry jam. The default Canadian pick for a tomato glut.
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Check price on Amazon.ca →The method (a slow afternoon)
- Sieve. Simmer quartered tomatoes until soft, then run through a food mill to remove skins and seeds.
- Reduce — slowly. Return the purée to a wide pot and simmer gently, stirring often, until it’s thick enough to mound and hold its shape on a spoon. Budget 2–4 hours; stir more the thicker it gets. A low oven finishes it without scorching.
- Acidify each jar — before filling it. 1 1/2 tsp (7.4 mL) bottled lemon juice into every hot 250 mL jar. The acid goes into the empty jar, not into the pot, so every jar gets the same amount.
- Fill. Pack the hot paste in, pressing out air pockets, leaving 1 cm (½ inch) headspace. Wipe rims, apply fresh SNAP lids fingertip-tight.
- Process 45 minutes in the boiling water bath at altitudes up to 1000 ft (305 m); add time above that per your altitude band. Time starts at a full rolling boil.
- Cool and check. Rest 5 minutes in the canner, lift to a towel, and leave 24 hours before checking seals.
Freeze it instead
The honest shortcut: freeze the paste and skip canning entirely. Since you use paste a spoonful at a time, this is often the better call.
- Reduce the tomatoes to paste exactly as above.
- Spoon into an ice-cube tray (about 1 tbsp per well) and freeze solid.
- Pop the cubes into a labelled freezer bag. Grab one cube per recipe.
No canner, no acidification math, no heat-penetration worry — see how to freeze tomatoes for the full freezing approach.
Related tomato guides
Altitude adjustment
Process times in a boiling-water canner are written for altitudes up to 305 m. Above that, water boils below 100 °C and the time printed in the recipe is no longer enough. Find your elevation, then add the minutes Bernardin publishes for that band.
| Elevation (m) | Elevation (ft) | Add to processing time |
|---|---|---|
| 0 – 305 | 0 – 1,000 | None — use the recipe time as written |
| 306 – 915 | 1,001 – 3,000 | +5 minutes |
| 916 – 1,830 | 3,001 – 6,000 | +10 minutes |
| 1,831 – 2,440 | 6,001 – 8,000 | +15 minutes |
| 2,441 – 3,050 | 8,000 – 10,000 | +20 minutes |
On the line between two bands, round up to the higher one. Slightly over-processing is safe; under-processing is not.
Bernardin’s published tables stop at 3,050 m.
Find your Canadian city · Full altitude guide
Figures from Bernardin, “How do I can at a high altitude?” (bernardin.ca). Confirm against your own Bernardin edition before you start — a book edition and the website can differ.
Frequently asked questions
Is it safe to water-bath can tomato paste?
Yes, with a tested recipe — but paste has two safety wrinkles. First, like all tomatoes it must be acidified: Bernardin puts 1 1/2 tsp (7.4 mL) of bottled lemon juice into each 250 mL jar, added before the jar is filled. Second, paste is dense, so heat penetrates slowly; Bernardin compensates with a small jar (250 mL) and a long process — 45 minutes at up to 305 m. Don't scale up to bigger jars or shorten the time — both can leave the centre under-processed. If that feels fussy, freezing is the safe, simple alternative.
Isn't it easier to just freeze tomato paste?
For most households, yes. Paste is used a tablespoon or two at a time, so freezing it in an ice-cube tray and popping the cubes into a freezer bag is faster, needs no canner, and skips the acidification and heat-penetration concerns entirely. Can paste if you want shelf-stable jars and no freezer space; freeze it if you just want it handy. Both are legitimate.
How many tomatoes does it take to make paste?
A lot — paste is the most concentrated tomato product there is. Expect roughly 5–6 kg (11–13 lb) of tomatoes to cook down to only 2–3 × 250 mL jars, because you're evaporating most of the water. Start with paste tomatoes (Roma, San Marzano) rather than watery field tomatoes; they have more flesh and less water, so the reduction is shorter and the yield higher.
Why is my paste scorching on the bottom?
As tomato paste thickens it sticks and scorches easily. Use a wide, heavy-bottomed pot, keep the heat gentle, and stir often as it reduces — more often the thicker it gets. Some Canadian canners finish the reduction in a low oven (spread on a large pan, stirred occasionally) to avoid stovetop scorching. Whichever way, it's a slow project — budget a few hours.
Sources
- Bernardin Complete Book of Home Preserving (latest edition)
- Health Canada — Home canning safety (https://www.canada.ca/en/health-canada/services/general-food-safety-tips/home-canning-safety.html)