How to make strawberry jam

Place three clean 500 ml mason jars on the rack in a boiling water canner. Cover the jars with water and heat to a simmer. Heat sealing discs in hot, not boiling, water. Keep jars and sealing discs hot until ready to use.

Wash, hull, and crush strawberries by hand with a potato masher. Using a food processor will destroy the natural pectin in the berries. Combine the strawberries and lemon juice in a large saucepan. Add butter or margarine and whisk in fruit pectin until dissolved. Over high heat, bring the mixture to a rolling boil and add the sugar. Stirring constantly, return the mixture to a rolling boil that cannot be stirred down. Boil for 1 minute, stirring constantly. Remove from heat and skim off foam.

Quickly ladle jam into a hot jar, leaving .5 cm of headspace. Using a spatula, remove air bubbles and adjust headspace, if required, by adding more jam. Wipe the jar rim clean to remove any food residue. Place lids and bands on jars and screw tight until resistance is met. Do not over tighten. Return the filled jar to the rack in canner and repeat for remaining jars.

Cover the jars with water. Cover canner and bring water to full rolling boil before starting to count processing time. Boil filled jars for 10 minutes.

Remove canner lid, wait 5 minutes, then remove jars without tilting and place on a protected work surface. Cool undisturbed for 24 hours. Do not retighten screw bands.

After cooling, check jar seals by pressing the top of each seal. If they do not bounce back it means the seals have taken. Remove screw bands and wipe and dry bands and jars. Store screw bands separately or replace loosely on jars. Label and store jars in a cool, dark place. For best quality, use home canned foods within one year