The Idiot-Proof Blueberry Jam That I Finally Got Right

Every year for the past three years I have tried to make blueberry jam. In part because living in a place where blueberries grow so freely is a novelty to me, so when I take my kid and her friends picking I always end up coming back with way more than is reasonable. I freeze some, make baked stuff out of others, and try to make jam out of the rest.

They say -- the "theys" that know -- that blueberry jam is the easiest jam to make, because blueberries are so rich in pectin (the thing that makes jam gel) that you don't have to add anything to them except for sugar to end up with jam.

I begin every year with the assumption that blueberry jam is foolproof, and every year I mess up.


The thing is, blueberries are SO high in pectin that if you cook the jam too long, it will turn into something more like a fruit jelly candy -- practically solid rather than spreadable. And very few of the recipes I've come across give you much by way of specificity when it comes to how long to cook the berries in order to reach the proper gelling point. (Most urge you to rely on a divination method involving a frozen plate, which is way too mystical for me.)

Today, however, it was different. Today I managed to succeed at what is supposed to be such an easy process that Martha Stewart lists it as a great recipe for kids to make. I couldn't be prouder.

The secret: Use a fairly big pot relative to the amount of stuff in it, and use an instant read thermometer. Also, use your eyes and a timer.

Blueberry Ginger Jam
Makes 1 pint

The jam will keep for a month or two in the refrigerator. It won't last that long, though. My daughter would like you to know that she was the one to suggest the ginger.

2.5 c blueberries, freshly-picked is best
1 c plus 2 TB sugar
juice of half a lemon
a healthy pinch of salt
2 coins of ginger

1. In a 3.5 qt saucepan, combine all ingredients. Take a potato masher and give the pot 5 mashes -- you want to crush some but not all of the berries. Turn the heat on to medium high and stir for a minute or so until you see the sugar melting and the juices start to release. Allow to come to a vigorous boil, stirring occasionally. If you see any foam rising to the top (greyish or whitish) skim it off (I didn't).

2. Allow to boil for 10 minutes. Starting at 8 minutes in, check the temperature with a candy thermometer or instant read thermometer. The ideal setting temperature is 220º F, which should happen at the 10 minute mark. At that point, you'll see that when you dip a spoon into the jam, instead of quickly dribbling off the jam will fall off the spoon in large droplets.

3. Remove the ginger coins and discard. Transfer the jam to a very clean pint jar that has been rinsed out with boiling water. (It needs to be warmed -- otherwise it might crack when you put hot jam in it.). Ladle the jam into the jar and cover; allow to cool on the counter and then transfer to the fridge. It will set up in about an hour.