Marmellata di pere

Mix pears, lemon juice, fruit pectin, cinnamon, cloves, allspice, and nutmeg in a large heavy pot; bring to a boil, stirring constantly. Add sugar all at once, stirring, and bring back to a full rolling boil. Boil for 1 minute. Mix in butter to settle foam.

Sterilize the jars and lids in boiling water for at least 5 minutes. Pack the pear jam into the hot, sterilized jars, filling the jars to within 1/4 inch of the top. Run a knife or a thin spatula around the insides of the jars after they have been filled to remove any air bubbles. Wipe the rims of the jars with a moist paper towel to remove any food residue. Top with lids, and screw-on rings.

Place a rack in the bottom of a large stockpot and fill halfway with water. Bring to a boil and lower jars into the boiling water using a holder. Leave a 2-inch space between the jars. Pour in more boiling water if necessary to bring the water level to at least 1 inch above the tops of the jars. Bring the water to a rolling boil, cover the pot, and process for 10 minutes.

Togliete i barattoli dalla pentola e disponeteli su una superficie di legno o ricoperta da un panno, a qualche centimetro di distanza l'uno dall'altro, finché non si saranno raffreddati. Una volta raffreddati, premete la parte superiore di ogni coperchio con un dito, assicurandovi che la chiusura sia ermetica (il coperchio non deve muoversi né verso l'alto né verso il basso). Conservate in un luogo fresco e buio.