Blueberry-Blackberry Jam

I make blueberry-blackberry jam every year, and this was the best batch to date – perfectly tart, and not too many pesky blackberry seeds.  If you have never “canned” anything, you need to familiarize yourself with the simple techniques and necessary safety precautions before making this recipe.  The Ball Blue Book of Canning or the new and updated Ball Complete Book of Home Preserving are both excellent resources.  Ball books are full of thorough, easy to follow instructions and tips and fabulous, time-tested recipes.  I have never made anything out of a Ball book that was a flop!

There are lots of ways to make jams these days: freezer jam, added pectin with artificial, low or lots of sugar, and my favorite method – old school with no added pectin and not too much sugar.  Modern recipes cook up very quickly, but they require added pectin.  Jams made with added pectin and several cups of sugar come out like candy.  Recipes with added pectin and little sugar have a really odd, wimpy texture and do not keep well.  They don’t have enough sugar to truly preserve them, which is why they are often stored in the freezer (or they mold very quickly if you store opened jars in the fridge).  I don’t get the allure of putting freezing cold, runny jam on your toast, nor do I appreciate my jams going moldy once I open them.  I prefer the old fashioned method of using a small amount of sugar and no added pectin and then cooking the fruit to the natural gelling point.  The “gelling point” is a magic confluence of the perfect temperature, sugar saturation and water content.  It happens at 220 F, and usually takes about 15-20 minutes to reach.  Learning to recognize the gelling point takes a little practice.  I give some basic information in the recipe below, but the Blue book has a much more thorough and helpful discussion of this technique.

Yes, it takes more time and effort to make jams the old-fashioned way, and yes, there is more risk of under or overcooking the jam.  However, once you master this age-old technique (c’mon, you can do this!!!) the jams and preserves you create will be far superior to anything in the store or anything made in the modern “convenient” way.  It is very much like the difference between instant coffee and grinding your own high-quality beans and brewing them to perfection.  The old fashioned method creates preserves that are intensely flavored and pleasingly tart (because you cook off a lot of the water), with a texture much like the natural fruit (because you don’t use much sugar, the preserves don’t come out chewy and candy-like).  To me, if you are not going to use this method, you may as well buy high-quality preserves at the store.  However if you have some beautiful fresh fruit and a little time, there is great satisfaction in savoring your own homemade preserves.

Blueberry Blackberry Jam

  • 12 oz blackberries
  • 12 oz ripe blueberries
  • 12 oz slightly underripe blueberries (or ripe ones, if you aren’t picking them yourself)
  • 2 cups sugar
  • 2 Tbsp. fresh lemon juice

In a large heavy-bottomed stainless steel pan combine fruits, sugar and lemon juice.  Lightly crush fruit with a potato masher and stir until sugar starts to dissolve.  Macerate fruits and sugar for 2 hours, stirring every 20 minutes or so.  Place 2 saucers in freezer.  Bring fruit mixture to a boil over medium-high heat, and mash fruit with potato masher until all berries are broken down (you don’t want a puree, just pop all the blueberries – the heat will break them down).  Reduce heat to medium and boil, stirring frequently until mixture reaches the gelling point – about 15-20 minutes.  When jam begins to thicken, start testing for doneness.

To test jam for doneness either use a very accurate digital thermometer to check temperature (you are looking for 220 degrees F), or use the plate test:  remove pot from heat and place 1 tsp. jam on plate in freezer; wait 1 minute; take plate out of freezer and lightly push jam with finger – if it shows a “skin” on top it is done, if it is runny, continue cooking jam and retest.

When jam tests done, ladle hot jam into sterilized canning jars, leaving ½” headspace (you can use 4 oz, 8 oz or 12 oz jars).  Wipe rims, place new lids on top and seal with bands.  Process jars 10 minutes in boiling water bath.  Turn off heat, remove lid from canner and allow jars to cool 5 minutes before removing them from water.  Makes around 5 half-pints.

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