Whether you like your jam soft and slushy or shapely and firm, you need to achieve a set of some kind. You can use sloppier jams to spread in a Victoria sponge, to sweeten oats with natural yoghurt or smoothies, while jams that hold their form are better on a cheese plate or used in cooking. Whichever variety you prefer, you need to learn how to set jam. If you have had a few failed endeavours it may be time to investigate the subject a little deeper.
It’s all about the pectin
Pectin is a fibrous material found in fruits and vegetables, in varying quantities. It binds with the sugar in setting jam to give it structure. Fruits with higher natural levels of pectin include apples, cranberries and blueberries, whereas strawberries, rhubarb and pears are much lower in pectin. Lower pectin fruits will need a little help to set, in the form of a pectin additive or by combining them with higher pectin fruits. Apples with blackberries, for example. Lemon juice added to the jam mixture can have a similar effect.
How to test setting jam
There’s no dark art involved in finding the setting point and it is the key factor in how to set jam. You should be able to tell if the jam is approaching its time by dragging a wooden spoon through the pan, then lifting it and watching how the jam drops off. If it is runny and thin and falls right off the spoon, it’s not ready. If it hangs in large droplets and falls slowly, it’s worth testing. There are two easy ways. One is to use a sugar thermometer to make sure you cook the jam to 105C, which it the point at which sugar binds with pectin. Alternatively, before you start cooking, put a couple of small saucers in the freezer. When you think your jam is about ready, put a drop onto a cold saucer and leave it for a minute, then prod gently with a fingertip. If a slight skin has formed on the surface of the jam dollop, which wrinkles as you touch it, then the jam has reached setting point. If not, keep cooking and re-test regularly.
Patience with setting jam
You can’t rush a good job! Sometimes jam takes its time reaching a set. Even if it seems reluctant to set in the pan, sometimes a week in the jar produces a better result.