How to Make Seedless Blackberry Jam
This jam takes some effort, but the results are wonderful. The seedless jam is intense in flavour and easy on the teeth. It improves with age. If you want to make regular blackberry jam, follow the instructions below but skip the removal of the seeds in step 1.
When you pick the berries, if you cannot make jam within a day or two, put them into 2 cup plastic containers and freeze immediately without rinsing, as they keep better that way. When you are ready to make jam, just dump the frozen berries into the pot and proceed.
Allow about 5 hours for the whole process. You will not be working the whole time, but you have to be there to stir and monitor. Have a book handy that you can hold in one hand and read while you stir with the other.
Essential equipment includes a candy thermometer and food mill (you can use a sieve but that takes a strong arm and stamina).
1. Making the seedless fruit puree.
2. Cooking the jam.
3. Preparing the sealer jars.
4. Putting the jam into the jars.
Step 1: Making the seedless puree.
Try doing this step before lunch so the puree can cool while you eat lunch.
Use anywhere from 4 to 12 cups of blackberries. Rinse fresh berries and put into a large heavy pot with only the water clinging to the berries or use frozen without rinsing. Put over low heat and be patient and stir occasionally while the fruit comes to a boil. Do not try to rush with high heat as you will scorch the berries. Simmer the fruit and stir until it turns very liquid. Take the pot off the heat and allow to cool somewhat while you have lunch. Put a sieve or food mill over a bowl and push the cooked berries through, saving the puree and discarding the seeds.
Step 2: Cooking the jam.
Remove any seeds clinging inside the pot, and measure the puree back into it, counting how many cups. Then add one cup of white sugar for every cup of puree. This seems like a lot, but this is what jam is – an amalgam of sugar and fruit. The sugar prevents bacterial growth and when cooked with the fruit to a high temperature, binds with the pectin in the fruit to create jam. The addition of the sugar will have increased the volume a lot, and when cooking the jam it really boils up, so you may have to use two pots. Each pot should be only about 1/8 full when you start. Put the pot back over medium low heat and stir while it comes to a boil. Let it come to a full rolling boil (now you see why you need a big pot), then turn down to a fast simmer. Attach your candy thermometer and stir occasionally while you wait for it to come to the jam creation temperature of 105 C. / 220 F. This can take an hour or more and seems painfully slow. The book is useful at this time.
Step 3: Preparing the sealer jars.
While the jam is cooking, get the jars ready. I like small wide mouth jars. Pour boiling water into each jar, then put upside down on a clean towel to drain. Put the new snap lids into a small pan of water, ready to boil for 5 minutes before sealing. Get a heatproof surface ready to hold the jars once filled – I use my large wooden carving block.
Step 4: Putting the jam into the jars.
Boil the snap lids for 5 minutes to soften the sealing compound. Put the jars on the heatproof surface. Use a canning funnel and fill each jar to within ¼ inch from the top – do not leave a larger gap, slightly less is better. Use a clean damp cloth to wipe the rim of each jar as there must be no residue to interfere with the seal. Put a hot snap lid on each jar and screw on the bands firmly. Leave the jars to cool. Within the hour you should hear each lip “snap” down to seal. Do not touch the screw bands again as they will tighten as they cool and hand tightening again may break the seal. Label each jar on the snap lid with the date and put aside in a cool dark place to store. If any jar does not snap seal, refrigerate and eat within a month. The sealed jars will keep for 3 years, and like wine, will improve and mellow with age.