Place 7 clean 250 ml mason jars on a rack in a boiling water canner. Cover jars with water and heat to a simmer (180°F/82°C). Set screw bands aside. Keep jars hot until ready to use. Preheating Bernardin® lids is not advised.

The sealing compound used for our home canning lids performs better at room temperature than it does pre-heated in simmering water (180°F). Simply wash lids in hot, soapy water, dry, and set aside until needed.

Preheating can lead to less vacuum being achieved during water bath canning, and to buckle failures during pressure canning. Wash, peel, seed and finely chop or crush papayas. Measure 2 cups (500 ml). Wash and grate 2 tbsp (25 ml) grapefruit peel.

With a sharp knife, remove remaining peel and pith from grapefruit. Working over a bowl to catch juice, remove grapefruit segments; discard membrane. Measure 2 cups (500 ml) grapefruit, including juice. Measure sugar; set aside.

In a large deep stainless steel saucepan, stir together prepared papaya, grapefruit and water, 1/2 tsp (2 ml) butter or margarine to reduce foaming, and Bernardin Original Pectin and whisk until dissolved. Over high heat, bring mixture to a full rolling boil. Add all of the sugar.

Stirring constantly, return mixture to full rolling boil that cannot be stirred down. Boil hard 1 minute, stirring constantly. Add the orange liqueur if desired. Remove from heat; skim off foam, if necessary. Ladle hot jam into a hot jar to within 1/4 inch (0.5 cm) of top of jar (headspace).

Using nonmetallic utensil, remove air bubbles and adjust headspace, if required, by adding more jam. Wipe jar rim removing any food residue. Centre sealing disc on clean jar rim. Screw band down until resistance is met, then increase to fingertip tight. Return filled jar to rack in canner.

Repeat for remaining jam. When canner is filled, ensure that all jars are covered by at least one inch (2.5 cm) of water. Cover canner and bring water to full rolling boil before starting to count processing time. At altitudes up to 1000 ft (305 m), process - boil filled jars - 10 minutes.

When processing time is complete, turn stove off, remove canner lid, wait 5 minutes, then remove jars without tilting and place them upright on a protected work surface. Cool upright, undisturbed 24 hours; DO NOT RETIGHTEN screw bands. After cooling check jar seals.

Sealed discs curve downward and do not move when pressed. Remove screw bands; wipe and dry bands and jars. Store screw bands separately or replace loosely on jars, as desired. Label and store jars in a cool, dark place. For best quality, use home canned foods within one year.

Processing: At altitudes up to 1000 ft (305 m), process - boil filled jars - 10 minutes - 10 minutes.

Altitude-adjusted processing table: At altitudes up to 1000 ft (305 m), process - boil filled jars - 10 minutes