Seedless Blackberry Jam - cooking recipe

Ingredients

2 1/2 lbs blackberries
1 cup green apple pectin stock
3 cups sugar
2 tablespoons lemon juice

Preparation

Place the blackberries in a blender and blend until they are all crushed. You may need to do this in two batches depending on the size of your blender.
Strain the blackberry puree through a mesh strainer to remove the seeds - stir and press on the puree while it is in the strainer - you want to get as much puree as you can.
Measure out the blackberry puree; you should have about 4 cups. If you don't have 4 cups add water to the puree until you have 4 cups.
Place 3 small plates or saucers in the freezer.
In a preserving pan, combine the blackberry puree, 1 cup of Green Apple Pectin Stock, 3 cups of sugar, and 2 tablespoons of lemon juice over medium heat, stirring gently until the sugar is completely dissolved.
Raise the heat to medium-high and boil for 15 minutes.
After 15 minutes of cooking, check the set (it may take up to 30 minutes of simmering over medium high heat for the jelly/jam to reach the set stage - it depends on what kind of pan you are using and how high of heat you are using).
Use the cold plate test to check set: take the pot of jam off the heat (if you don't remove the jam from the heat while you check the set it could over-cook and become rubbery or hard, if the jam is indeed already set) .
Place a drop of the jam mixture on one of the saucers you've kept in the freezer, & place the plate back in the freezer for 1 minute. After 1 minute, take the saucer out of the freezer and nudge the drop of jam with your finger. If it \"wrinkles\" when you nudge it with your finger it is done. If the jam is not set, continue cooking over medium-high heat, checking the set again every 5 minutes.
When the jam is set, ladle the jam into canning jars, leaving 1/4\" headspace. Wipe the rims of the jars with damp paper towels to remove any jam which got on the rims or the threads. Place the lids and the bands on the jars, just tightening the bands fingertip tight.
Process in a boiling water bath for 10 minutes, then remove and let sit, undisturbed, for at least 12 hours before checking seals. It is important to let them sit undisturbed for 12 hours because the sealing compound on the lids is still cooling and hardening, completing the seal. While the jars cool, you will hear a \"plink\" type sound from each jar - this is the jars completing the vacuum seal as the final air escapes the jar. After 12 hours have passed, remove the bands and check the lids - press down in the center of the lid. If you cannot push the lid down any further, the jar is sealed. If the lid \"gives\" a bit, and you can push it down, the jar did not seal. You can either put the band back on the jar, and reprocess it for another 10 minutes, or you can just put it in the fridge and use it within 3 months.