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Canning Class: Strawberry jam that works

Just Right Strawberry Preserves (Deb Lindsey/For The Washington Post)

How is it that the first fruit of summer turns out to be the star of one of the more difficult jams to make? Doesn’t seem fair. Even experienced home food preservers will admit to wrestling with strawberry jam. It’s that tricky.

Yet all those gorgeous strawberries are calling out to eager preservers who struggle and then hold a grudge. I’m redeeming canning’s reputation with a recipe that puts strawberry jam making in its place. Reliable, consistent and downright delicious — not sad, angst-ridden and frustrating — this recipe takes about two hours over two days, uses common kitchen equipment and results in a reasonable number of ruby-red jars of superb jam. 

Getting fruit preserves to set is all about pectin, a naturally occurring element. Some fruits have a lot of pectin while others have almost none. Pectin binds with sugar and lemon juice to form the gel that sets the preserves. Achieving consistent gel when making jam with low-pectin fruits, such as berries, requires nothing more than the addition of a Granny Smith apple. Once it’s grated directly into the berry-sugar mixture and offered a long luxurious maceration (rest period), the fruity syrup becomes suffused with the apple’s natural pectin.

When that syrup is reduced and the berries are incorporated, the mixture comes together into a not-too-firm, berry-studded, tart jam.

Adding an apple is only half the battle; one must deal with nuance as well — a nice way to say that every batch has quirks. Too little boiling and the preserves will be runny; too much and they will be bouncy. Wait for the foam on the surface to nearly clear, at which point the jam will be set. Any bits of thick foam that persist are easily dispersed with a pinch of butter and a lot of stirring.

To understand jam making takes experience. Whatever you capture in the jar will be delicious. If the jam turns out a bit loose, call it sirop and pour it, warm, over waffles. If it’s rubbery, warm it in a saucepan and add water until it has thinned considerably. Bring to a boil, cool, then ribbon through softened vanilla ice cream. Refreeze the ice cream, and declare victory.

The accompanying recipe makes rich preserves. Please do not alter the amount of sugar. You might think it would be “healthier” to do so, but that balance of fruit, sugar and lemon juice is the very essence, the science, of jam making. When the ratios are changed, the gel, the color, the flavor and the shelf stability of the jam are at risk. 

Strawberries grown locally are plump and juicy and irresistible. They have not been refrigerated in the deep cold of a long-haul truck. Instead, they are picked when ripe and sent right to market. Taste one before you commit. Seek out ripe, locally grown, recently harvested, flavorful berries. One-quarter of them should be slightly underripe.  

We’re coming into the Mid-­Atlantic’s peak season for strawberries. It’s a great time for pick-your-own farms, roadside stands and farmers markets, where the air will be full of that sweet berry smell. Open a jar of this jam in gray, bleak February, and it will transport you.

Canning Class appears twice a month. Barrow’s first cookbook, “Mrs. Wheelbarrow’s Practical Pantry: Recipes and Techniques for Year-Round Preserving” (W.W. Norton), will be published in the fall. She blogs at She will join Wednesday’s Free Range chat at


Just Right Strawberry Preserves

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