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Thursday, 10 September 2009 |
People frequently ask me why their jams don't set. After putting fruit up in jars every year for roughly a quarter of a century, I've developed a few basic rules for good jam.
Generally speaking, the key to getting jams to “set” is to cook fruits that are naturally high in pectin (with the appropriate amount of sugar) to 220F. That’s quite a bit higher than the boiling point and the concentrated nature of fruit puree or juice saturated with all that sugar is what makes the higher temperature possible. If you pick the fruit too ripe, it won’t have much pectin; as the fruits ripen and soften over time, the pectin gets converted into sugar. For proper gelling and flavor, you also need a certain amount of acid in the fruit; it should taste decidedly tart before the sugar is added. So start with fruit that’s firm and slightly under ripe, bring it to a boil, then add the sugar and, as quickly as you can without burning it, bring it up to temp. Be sure to work in small batches. A big pot of fruit will never come up to temp before it takes on an overcooked taste. Bring up to the jelling point before it evaporates or burns. To gauge the temperature, use a candy thermometer, or watch how the jam rolls off the back a of a metal spoon. When it’s under done, the jam will roll off in two distinct streams; when it’s ready the streams will come together to from a “sheet.” To sum it up:
1.) Use firm, barely ripe fruit and add lemon juice if the flavor is flat.
2.) Bring a small batch (no more than 4 cups) of fruit to a full boil.
3.) Add an appropriate amount of sugar; equal to the weight of the fruit.
4.) Quickly bring the temperature up to 220F; at this temp, the fruit will form a sheet as it falls off the back of a spoon.
5.) Put the jam up immediately in sterilized jars. (Four cups of fruit will yield about six cups of jam.)
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