Making Strawberry Jam
Strawberry jam is a matter of cooking down fresh fruit with sugar and enough acidity to allow the natural pectin to set. The goal is to cook the mixture rapidly to evaporate water and reach the gelling point—around 220°F—without dulling the bright red color of the fruit. Proper preparation is defined by the moment the bubbles become thick and sluggish, signaling that the jam is ready to jar.
Watch the temperature, not the clock.
Jam is a chemical reaction; once the sugar is added, you must monitor the boil continuously to prevent scorching at the bottom of the pot.
- wide, heavy-bottomed stainless steel pot
- candy thermometer
- slotted spoon
- canning jars with new lids
- water bath canner or deep stockpot
What goes in.
- 4 lbfresh strawberries, hulled and quartered
- 4 cupsgranulated sugar
- 1/4 cupbottled lemon juice
Testing for the Set
Place a small saucer in the freezer before you start. When you think the jam is ready, drop a teaspoon of it onto the cold plate; if it wrinkles when you push it with your finger, it will set firmly in the jar.
The method.
Macerate the fruit
In the heavy pot, combine the strawberries and sugar. Stir well and let them sit for at least 30 minutes until the sugar draws the juices out of the berries.
Bring to a boil
Place the pot over medium-high heat. Add the lemon juice and stir until the sugar is completely dissolved. Once boiling, do not walk away.
Cook to temp
Boil the mixture hard. Use the thermometer to track the temperature. Skim off any light foam that gathers on the surface with your slotted spoon.
Check the set
When the jam reaches 220°F or passes the cold plate test, turn off the heat immediately to preserve the color.
Jar and process
Ladle the hot jam into sterilized jars, leaving 1/4 inch of headspace. Wipe rims clean, apply lids, and process in a boiling water bath for 10 minutes.
Other turns to take.
Vanilla Bean
Split one vanilla bean and scrape the seeds into the pot before the initial boil for a fragrant, floral finish.
Black Pepper
Add one teaspoon of freshly cracked black pepper during the last five minutes of cooking to cut through the sweetness.
When it doesn't go to plan.
Use a wide pot rather than a deep one; the larger surface area allows steam to escape faster, shortening the cooking time.
Do not double the batch size in one pot, as the longer cooking time required for a larger volume will result in a darker, less flavorful jam.
If the jam fails to set, you can re-boil it with a small amount of commercial pectin, though the texture will be slightly different.
The ones that keep coming up.
Why did my jam turn brown?
The jam likely cooked too long. High heat for an extended period caramelizes the sugar, turning the bright red fruit into a dull mahogany color.
Can I reduce the sugar?
Sugar is required for the gelling process when not using commercial pectin. Reducing it significantly will result in a syrup rather than a spreadable jam.
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