Preserving Strawberry Jam

Today marks my 3rd strawberry jam making demo at the Ann Arbor Farmer's Market.  This year, the market is piloting a Wednesday evening market, which is wonderful for people like me that work during the day.   I am looking forward to canning outdoors this evening with my friend Martha.  I've written lots about canning strawberry jam on this blog...if you want to check it out - zip over to the search box on the right and look up  "strawberry jam" to see how my thoughts have evolved on the subject.    Over the years, I have optimized my approach.  No more boxed pectin, no more "wrinkle test".    Measuring gel temp is where it's at!  This is how I demonstrating the jam last night.

Strawberry Jam with Homemade Pectin
Makes 9 half pint jars

Homemade pectin

6 tart apples,blossom and stem ends removed, chopped up, core and seeds and all
2 lemon chopped up, peel and seeds included.

Cook this down until soft, and put through a food mill.  Set aside.

Note to self for the fall.....

The pectin puree could be made in the fall when apples are in season, and instead of lemons, save lemon rinds and seeds in the freezer after they've been juiced for other things.    The rinds and seeds are where all the pectin is in the lemon.   The puree can be canned in pint jars like apple sauce - i.e. process in a boiling water bath for 10 minutes with 1/2 inch headspace.  Come spring, the pectin will be ready to go to make jam. 
 
For the jam
 
3 quarts strawberries, halved and hulled
6 cups sugar
Homemade pectin

I like to use a digital meat thermometer to measure the temperature of my jam.  I have one I bought years ago for $50, but the prices have really come down and there's a great selection now.  This one is recommended by Cooks Illustrated and it's only around $20. 
 
To make the jam, put all ingredients in a tall pan or stockpot and stir.  Boil gently until mixture reaches 220 F (for <1000 ft below sea level).   this is the jelling temp - it's 8 degrees above the boiling point of water.    Note that this will take a long time - it sometimes takes up to an hour.  It might sit at 217 F for a long time.  Don't worry!  It all depends on how much water is in the berries and how much pectin is already in them, and that varies from crop to crop.  Don't even think about giving up when it's at 219 F, thinking it's boiled long enough.  It hasn't - trust me!  Ladle into hot jars, leaving 1/4 inch headspace.  Process in a boiling water bath for 10 minutes.