Preservation · Half day · Intermediate
Water-Bath Canning High-Acid Foods
pH 4.6 or lower, tomatoes acidified with 2 tablespoons of bottled lemon juice per quart, 1–2 inches of water, and a full boil that never stops.
This is for educational purposes only. Not professional medical, electrical, or safety advice.
Warning
A longer ordinary water bath is not an approved substitute for pressure canning low-acid foods. Milk, cream, butter, cheese and jars of fat are not made safe by using a fruit-canning schedule, and acidifying an invented mixture does not establish a safe heat process.
- 01
Use only eligible foods and tested formulations
Acid foods have a pH of 4.6 or lower — many fruits, tested pickles, jams and properly fermented sauerkraut. Tomatoes and figs need the acidification specified by their tested recipes.
- 02
Acidify tomatoes precisely
For whole, crushed or juiced tomatoes, NCHFP directs adding per quart 2 tablespoons of bottled lemon juice or ½ teaspoon of citric acid, and per pint 1 tablespoon of bottled lemon juice or ¼ teaspoon of citric acid. NCHFP also allows 4 tablespoons of 5%-acidity vinegar per quart, though flavor may suffer. Do not substitute an unknown-strength homemade vinegar.
- 03
Prepare jars and food as directed
Wash and inspect jars and use the recipe's pack method and headspace. Jars that will be processed 10 minutes or longer do not require separate presterilization; shorter processes require properly sterilized jars. Lid preparation follows the manufacturer.
- 04
Load a rack-equipped canner
Preheat the water to 140°F for raw packs or 180°F for hot packs, and cover jars with at least 1 inch of water — use 2 inches for processes longer than 30 minutes.
- 05
Follow an actual recipe schedule
As one example, USDA hot-packed applesauce with ½-inch headspace: 0–1,000 ft, pints 15 minutes and quarts 20; 1,001–3,000 ft, 20 and 25; 3,001–6,000 ft, 20 and 30; above 6,000 ft, 25 and 35. Those are applesauce times, not universal 'fruit' times.
- 06
Keep the boil continuous
Start timing when the water returns to a full boil, keep the canner covered, and maintain the boil throughout. If boiling stops, return to a boil and restart the complete processing time. Add boiling water as needed to keep the jars covered.
- 07
Finish without disturbing the seals
Turn off the heat, remove the canner lid, wait 5 minutes, then lift the jars upright. Cool them 12–24 hours and test the seals — a sealed lid is concave and does not spring up when pressed.