Cut out any little knots or seeds that you may come across while cutting the pineapple.
Pectin is a fruit extract that helps to thicken and bind jams and jellies. Different varieties of pectin sometimes call for different amounts of water to be added. Check and follow the instructions on your packet if you are supposed to use a different amount of water than one cup.
The jam is now ready to be canned or to be eaten once it has cooled down!
You can also stick a thermometer into the jam. If it has reached 220 degrees F (104 degrees C), it has reached the jelling stage and should be ready. [10] X Research source
Make sure to use the canning jars that have the rings and the screw-on top. These jars provide an airtight seal and are optimal for canning. If you plan to eat the jam within the next few weeks, you don’t have to bother with the canning process: you can simply pour the jam into a jar and keep it refrigerated.
Don’t fill up the jars completely. Leave about a ¼ inch (0. 6 cm) of space at the top.
You should see a small indent at the top of the jars after you take them out of the bath. This means that they are sealed and won’t spoil for about 18 months! Again, you can skip this step if you plan on eating the jam within the next month or so.
