The Cooking, Potting, and Sealing of Jams

Ingredients

Equipment Needed

• •Wide 6 to 8 quart heavy stainless-steel preserving pan
• •Broad perforated skimmer
• •Boiling-water canner or deep stockpot with fitted rack and lid
• •Eight 250 ml canning jars with new lids and screw bands
• •Canning funnel, jar lifter, and nonmetallic bubble remover
• •Long-handled spoon
• •Clip-on preserve thermometer, optional

Instructions

1. 1

   Keep the tested proportions

   Prepare the fruit, sugar, acid, and pectin exactly as directed by a tested formula for that particular preserve. This master method tells you how to cook, judge, pot, and seal the batch; it does not replace the fruit-specific proportions that control set, acidity, and safe storage. Do not reduce the sugar or enlarge the batch casually, because either change alters evaporation and may prevent a proper set.

   Use high-acid fruit or a tested formula that supplies the necessary acid. Low-sugar and low-acid preserves need formulas developed expressly for them.
2. 2

   Heat jars and water

   Wash eight 250 ml canning jars, their new lids, and screw bands. Inspect the jar rims for chips. Set the jars upright on a rack in the canning pot, cover them with water, and hold them hot at about 180°F (82°C) while the jam cooks. Wash the lids according to their maker's directions, but don't boil modern sealing lids unless instructed. Bring a kettle of extra water to the boil so the filled jars can later be covered by 1 to 2 inches (2.5 to 5 cm).

3. 3

   Boil wide and quickly

   Put the preserve mixture into a broad, heavy, nonreactive pan, leaving at least half the pan empty for the rising boil. Heat rapidly, stirring across the floor and into the corners with a long spoon. For whole-fruit jam, keep a strong but controlled boil and stir often enough to prevent scorching without crushing the fruit to paste. For strained jelly, use the most vigorous boil the pan safely contains; rapid evaporation protects its colour and fresh flavour.

4. 4

   Read the nappe

   As the preserve concentrates, its bubbles will become heavier and the surface easier to see. Dip a broad skimmer into the mixture, lift it clear, and watch the underside. At first the preserve runs off quickly in many small drops. Test frequently now, because the final change is fast. The nappe is reached when the preserve gathers toward the skimmer's centre and falls at long intervals in slow, heavy drops, corresponding to the large-thread stage in The Cooking of Sugar (No. 2344). A thermometer may read about 222°F (106°C) at sea level, but the skimmer remains the governing test because boiling temperature changes with elevation. If the drops still run thin, boil another 20 to 30 seconds and test again. If the preserve has tightened too far but has not scorched, ça se rattrape: remove it from the heat, stir in boiling water 1 tablespoon (15 ml / 15 g) at a time, return it to a full boil, and test again. If it smells burned, do not scrape the pan floor; transfer the untouched portion to a clean pan at once. A truly scorched flavour cannot be hidden.

5. 5

   Rest the preserve briefly

   Remove the pan from the heat the instant the nappe appears. Skim off any persistent surface foam, then let the preserve stand for 7 to 8 minutes. This short rest settles the boil and helps whole pieces of fruit remain distributed instead of floating into a cap. Do not wander away and let the batch cool until it sets in the pan.

6. 6

   Fill the hot jars

   Lift one hot jar at a time from the water and drain it. Ladle in the preserve through a canning funnel, leaving 1/4 inch (6 mm) headspace. Run a clean nonmetallic spatula around whole-fruit jam to release trapped air, then adjust the level if needed. Wipe the rim with a clean damp cloth, centre a lid over it, and tighten the band only to fingertip tight. An over-tight band prevents air from escaping during processing.

7. 7

   Process the sealed jars

   Lower the filled jars onto the rack without letting them touch. The water must cover the lids by 1 to 2 inches (2.5 to 5 cm); add boiling water if needed. Cover the pot, bring it to a full boil, and process for 10 minutes at elevations up to 1,000 feet (305 m), or for any longer time required by the tested fruit formula. Above that elevation, add 5 minutes up to 3,000 feet (915 m), 10 minutes up to 6,000 feet (1,830 m), 15 minutes up to 8,000 feet (2,440 m), or 20 minutes up to 10,000 feet (3,050 m). If the boil stops, bring it back fully and restart the processing time.

8. 8

   Cool and test seals

   Turn off the heat, remove the lid, and wait 5 minutes. Lift the jars straight up and set them on a towel with space between them. Leave them undisturbed for 12 to 24 hours, then remove the bands and press each lid at the centre; a sealed lid is concave and does not flex. Refrigerate any unsealed jar and use it promptly, or reprocess it within 24 hours with a new lid according to the tested formula. Label the sealed jars and keep them in a cool, dark, dry cupboard. Never use paper, glycerine, paraffin, or an inverted jar as the seal. Open one when the table needs toast, brioche, or a spoonful beside fromage blanc. À table!

Chef Tips

• •Use the widest heavy pan that leaves plenty of empty height above the mixture. A shallow batch loses water quickly and keeps its colour; a deep stockpot prolongs the cooking and dulls the fruit.
• •The old finger test for large-thread sugar asks bare skin to meet boiling syrup. Leave it in the book. The skimmer shows the same concentration without a burn, and an accurate thermometer gives a useful second opinion.
• •Whole-fruit jam and clear jelly want different handling. Stir jam enough to protect the pan floor, but leave jelly undisturbed once the sugar dissolves unless its tested formula directs otherwise.
• •Store properly sealed jars without their screw bands so a failed seal cannot hide beneath a tight ring. Once opened, refrigerate the preserve. If you find mold, fermentation, leakage, or an unnatural smell, discard the entire jar without tasting it.

Advance Preparation

• •Choose the tested fruit-specific formula before shopping and weigh every ingredient in advance. Once the final concentration begins, the stages follow one another too quickly for measuring sugar or searching for lids.
• •Wash and inspect the jars earlier the same day, but keep them hot until filling. A cold glass jar can crack when boiling preserve is poured into it.
• •The jars require 12 to 24 hours of undisturbed cooling before their seals are tested. Properly processed preserves keep best for about a year in a cool, dark, dry cupboard.

Frequently Asked Questions

Nutrition Information

1 serving (about 300g)