What is pectin?
Pectin, friends, is a polysaccharide (a type of carbohydrate) found in the cell walls of plants. We only care about it as it’s crucial for jam-making (and relishes and chutneys too) because it acts as a gelling agent and is what helps a preserve set. When combined with sugar and an acid, such as lemon juice, pectin causes a jam or marmalade to thicken to the desired, spreadable consistency. Without it, jam is runny. Pectin can also help jam last longer by reducing water activity, which inhibits microorganism growth. Plus, it stops the syrup and jam parts of your jam separating out over time as it sits in a jar. Waiting to be eaten. Yum.
Some fruits are naturally high in pectin, and these include apples, red currants, citrus fruits, quinces and plums. And tomatoes. Others are notably low in it and these include strawberries, cherries, blueberries, blackberries, peaches, rhubarb, ripe pears and raspberries. Apricots, feijoas, grapes, pears, gooseberries and slightly underripe pears are moderately high in pectin. Often, jam-makers will add either powdered or liquid pectin to low-pectin fruits to make a jam set; you can buy pectin from the supermarket. Or, they’ll combine a low-pectin fruit with a high-pectin one; apple with blackberries, strawberries with apple, rhubarb and sweet orange, pears and quinces, cherries and plums, tomatoes with passionfruit for example. And yes, tomato and passionfruit jam is lovely, in case you were wondering.
How do you tell if your jam is ready and will properly set when cool? There is an easy test for this. You pop a saucer into the freezer until it is very cold. Once you think your jam might be ready, you spoon a little of it onto the cold saucer, then you run your finger through the middle of it. If your finger leaves a clear trail that doesn’t close over, your jam is ready to bottle and will set. Simple!
