Commercial pectin helps thicken jams to give them a more spreadable consistency. The pectin here is optional, though the jam will be thinner without it. But a little liquid isn't a bad thing if you don't mind licking your fingers!
1. Grate pears using largest holes on hand grater. Combine grated pears with sugar, lemon juice, and ginger in large stainless steel pot.
2. Bring pear mixture to a boil. Reduce heat to medium-low, and cook 30 to 45 minutes, or until jam has thickened. Stir pectin into ¼ cup jam liquid, if desired, and add to jam. Cook 3 minutes more, or until jam is thick.
3. Meanwhile, sterilize jars and lids: Submerge jars in large pot filled halfway with simmering water, and lids in small pot of simmering water. Keep jars and lids in hot water until ready to use.
4. Remove jars one at a time from hot water, and fill with jam, leaving ¼-inch headspace. Seal with lids. Place canning rack or cake rack in bottom of large pot, and return sealed jars to pot, adding extra water to cover jars by 1 inch, if necessary. Bring water to a boil, and boil 10 minutes. Remove jars from water, and cool.