Jam, jelly and marmalade are made from fruit boiled with sugar until its setting point is reached. The essential setting agent in fruit is pectin: a naturally occurring soluble, gum-like substance present in varying amounts in the pips, skin or pith and flesh of most fruits. Pectin gels when it is heated with the natural fruit acid and added sugar. As the preserve cools down, the pectin gels enough to set the preserves, if the rations are correct.
The degree to which a preserve sets is dependent upon the ratio between the fruit pectin, acid and sugar. While most fruit preserves require between 375 – 500 grams of sugar for every 500 grams fruit, the levels of pectin and acid varies considerably between different types of fruits. Pectin and acid variations can even occur within the same type of fruit, according to its age. Under - ripe fruit contains more pectin that ripe fruit, so it is important not to use over-ripe or damaged fruit in your preserve. Over- ripe fruit will affect the setting point while damaged fruit will affect the flavour.
This table shows the pectin and acid content of common fruits and vegetables. Use this chart to create a myriad of different combinations of jams, jellies or marmalades that will set.
Combine low to medium pectin and acid with high pectin and acid fruits. For instance add lemon juice in apricot jam, combine blackberries and apples and add some lemon juice for a perfectly set blackberry jam, cherry plum jam and so on.
Once you get the hang of combining pectin, acid and sugar ratios, making preserves will be de-mystified. Be creative and you will be rewarded with a full pantry and accolades and orders from family and friends.
Home made preserves make wonderful personalised gifts. Use unusual jars and containers and add some colourful ribbon or raffia for a more natural look. Attach a hand made note card and your home made preserves will be transformed from an ordinary home made gift into an extraordinary work culinary craft.
How to determine the setting point
There are a number of different ways to determine if the jam has reached the setting point. Try a couple of different methods and find the one that you are most comfortable with. Good quality firm ripe fruit and getting the correct pectin, acid and sugar ratio may be the foundation of obtaining the perfect set, but practice, patience and observation will be your kitchen hand maidens.
While there may be some disappointments along the way, once you learn how to read your preserving pan while it’s boiling and understand how to combine fruits to provide additional pectin or acid, the preserving pan will reward you with a sense of achievement and a range of preserves that can be served at breakfast, lunch or incorporated into dessert. Unless the preserve has been brunt, any under set jam, jelly or marmalade can be used as the base for fruit syrups or sauces for steamed pudding, pancake or crepes and cakes.
Setting point for jam is 105C (220F) so a good way to test for setting point is to have a sugar thermometer clipped to the side of your saucepan, with the end dipped in the boiling jam mixture.
You can also check for setting point using the "wrinkle" test. Before cooking the preserve put 3 or 4 small heatproof plates in the freezer. Once your preserve has boiled for several minutes, take the pan off the heat and carefully spoon a little jam onto one of the cold plates. Let it stand for a minute then push the blob of jam with your finger, if the surface of the jam wrinkles then it has set, if it is still quite liquid then put the pan back on the heat and boil the jam for another 3 to 5 minutes before testing again.
Wooden Spoon – Flake Test
Stir the preserve with a wooden spoon and hold the spoon flat at 90 degrees to the pot. A preserve that will not set runs off the spoon quickly in a single thin drip line. When the preserve is ready, the drip line will be thicker and will want to form two lines and run from
Wrinkle test Flake test
Boil jam until it reaches 64 Brix. Boil your preserve, testing it regularly until it has reached the correct percentage of sugar (64 Brix). To test, lightly smear some preserve on to the glass plate, allowing it to cool slightly before covering it with the face plate. Look through the eye piece, into natural light, and read the brix scale. Re-test as required, making sure the glass plate and covering face plate are clean and dry in between each test. Refractors are often also used by home brewers to test the sugar content of brewing mixtures.
In simplest terms, the refractometer works much like a prism, it reacts differently to light (by giving a reading on a scale) depending upon the amount of sugar that is available in the liquid sample held between the daylight plate and the main prism assembly