Jams and jellies are a great way to preserve fruit. They are made by boiling fruit in water and sugar until it reaches a setting point. The fruit is primarily preserved by the action of sugar. As long as jams and jellies are made and stored appropriately (with clean equipment following a recipe then stored in a dry, cool place in an airtight container), they have a long shelf life.
An important component in jams and jellies is pectin. Pectin is a naturally occurring substance in fruit that is released, with the help of acid, when fruit is simmered. The setting point comes when sugar and pectin combine in such a way that when the mixture is cooled it will lightly set. Some fruits contain sufficient levels of pectin and acid to create good setting jams. Others have a medium amount of pectin and acids that produce jams and jellies that would set less hard.
Additional acid can be added for setting. The acid used in home preserves is usually lemon juice, or citric or tartaric acid. Low pectin fruits require the addition of commercial or homemade pectin (see below for recipe) to set. Alternatively, low pectin fruits can be mixed with high pectin fruits to create a solid setting jam or jelly.
Fruit with high pectin content includes: All citrus fruits ie. lemons, oranges grape fruit etc. cooking apples, crab apples plums, currants, quince, damson, gooseberries etc.
Fruit with medium pectin content includes: apricots, raspberries, blackberries, loganberries
Fruit with low pectin content includes: strawberries, rhubarb, pears, cherries, grapes, pineapple and figs.
Here is a test you can do to determine the level of pectin in the fruit you are using:
Simmer fruit (with water if necessary) until it is mushy.
Place a teaspoon of the juice from the cooked fruit into a glass.
When it is cool, add 3 Tablespoons of methylated spirits. Shake gently then leave for a minute.
If a jelly-like lump forms, it has a high level of pectin, and up to 3 cups of sugar can be added per 500g of fruit (or approx 1 cup of sugar per 1 cup of cooked fruit puree).
If two or three lumps form, it indicates less pectin, and you can add 2 cups of sugar per 500g of fruit (or approx ¾ cups of sugar to 1 cup of cooked fruit puree).
If several small lumps, or no lumps form, there is not enough pectin present for the jam to set, so you will need to add pectin, or mix with a high pectin fruit.
As mentioned, if you have low pectin fruit, you can either:
Mix them with a high pectin fruit. You can either create a blend, such as apple (high pectin) and strawberry (low pectin) jam, or add 1 teaspoon of lemon per 1kg of fruit.
Use a commercial pectin, in which case you will need to follow the directions.
Make your own pectin.
Recipe for homemade pectin:
Usually made with apples, you can also use other high pectin fruits.
Cut up apples without coring or peeling.
Put 2 ½ cups of water per 1kg of fruit in a saucepan and slowly bring it to the boil.
Simmer until the fruit is soft (about an hour)
Test for pectin, as above. If a firm, jelly-like lump forms it is ready to use. If not, simmer it for longer until a firm jelly-like lump forms.
Strain off the liquid, and bring the liquid to the boil.
Pour into hot, sterilised jars.
Use the homemade pectin within 4 months.
A good jam should have the following characteristics:
Retain the flavour and colour of the fruit used
Not be too sticky when scooped out of a jar with a spoon (it should slide off the spoon cleanly)
Have a sparkling appearance
Be solid or firm, not runny - but also not too firm as this indicates over-cooking