Jam 101

How to make your own delicious homemade jams.

by: Food24 | 29 Mar 2010

Fruits to use

Jams can be made from one fruit or a mixture of fruits, but the main trick to master is to achieve the right balance of acid, sugar and pectin so that it will set with vivid colour and taste. The best fruits are those with high levels of acid and pectin, pectin gels when heated with sugar and fruit acid. Fresh, slightly under ripened and perfect fruit should be used rather than overripe fruit because this is when the pectin level is highest and gives the best results.

A conserve is a preserve, which is made from whole or large pieces of fruit. It's made in exactly the same way as jam, but often has a softer set. It doesn't make as large a quantity as the jam equivalent.

Fruits with a good balance of acid and pectin: Grapes, sour quinces, cape gooseberries, all the citrus family, Granny Smith apples, sour guavas and sour plums.

Fruits with good pectin and low acid: Sweet apples, guavas and quinces, when using these fruit for jam, add up to 60ml lemon juice to each kilogram of fruit to increase the acid content. By adding lemon juice, at the same rate, also applies to fruits low in pectin and high in acid such as apricots, pineapples, rhubarb and sour peaches.

Fruits low in both acid and pectin: Most berries, cherries and sweet peaches, these need to be mixed with a fruit or fruit juice high in pectin or acid to make a successful jam.

Setting varies from fruit to fruit and is also weather dependent. Apricots and raspberries will gel quickly but an intensity of flavour will be achieved with continued cooking. Strawberries and peaches take a little longer to gel. All jam will improve in flavour if stored for about two weeks before using and, if properly bottled, will last in a dark, cool, dry place for about two years.

Microwave jam

Jams can be made in the microwave but don't use more than 500g of fruit at one time. The same method should be followed as with conventional recipes, cook in a large shallow container, covered or uncovered. Check constantly during the cooking period. The flavour and colour can be great in microwave-cooked jams.

Basic rules

  • Make small amounts at a time, never more than 2kg of fruit. The fruit layer should not be deeper than 3cm to allow for rapid evaporation of liquid. Shorter cooking gives the best flavour, texture and appearance.
  • Should fruit require washing, place in a sieve and run cold water over it, warm water will soften the fruit. If fruit is immersed in water, it absorbs too much liquid, which will make a jam watery. Allow soft fruits to dry on paper towel and dry hard fruits with a cloth. Avoid washing strawberries if possible and if you absolutely have to, wash before hulling or they'll absorb too much water. The preparation of any fruit should be done just before making the jam to avoid deterioration.
  • Use a large, deep, heavy-based pan to prevent boiling over or splashing. A wide pan allows for rapid evaporation of the liquid and jam will reach the setting point quicker.
  • The amount of sugar used depends on the fruit and ripeness, anything from two thirds to equal parts by weight of sugar to fruit. Warming the sugar in a low oven before adding it to the fruit, will help it to dissolve faster and reduce the boiling time.
  • The sugar must be stirred to dissolve it completely before the mixture is allowed to come to a rapid boil. Use a long-handled wooden spoon to avoid burning your hand. This is to prevent any sugar burning in the base of the pan or crystals forming in the jam. Once rapid boiling has begun the jam must not be stirred.
  • Test jams frequently, after they have boiled for about five minutes. If testing is left late, a jam can have boiled too long and passed its setting point. It will then never set. To test it, remove from the heat, cool a little on a saucer chilled in the freezer, and push with a finger, if it wrinkles and clings to the spot it is ready.
  • Skim with a slotted spoon to remove any scum and froth at the end of cooking. A knob of butter added during jam making will prevent a scum forming. Allow the jam to cool a little, to prevent fruit floating during setting in a jar, then pour into hot, dry and clean containers.
  • Jars must be sterilised, either in a dishwasher or boiled in a pan of water for 10 minutes. Remove them and allow to dry on paper towel, don't try to wipe them dry with a cloth because of hidden bacteria. Pour the jam into jars with a heatproof measuring jug, filling them to within 1cm of the rim. While still hot, cover with the lid, screwing tightly. Cover with a cloth in case of seeping and stand upside down so that the jam is in contact with the lid. Leave it to cool before turning upright. A vacuum will have been created and enough air expelled to prevent mould. Otherwise allow the jam to cool, pour a layer of molten wax over the entire jam surface and allow it to cool before screwing on the lid.

What could go wrong?

  • Jam not set? Could be due to lack of pectin or acid or insufficient sugar, under- or overcooking or boiling too slowly. If slightly soft, leave unsealed in a sunny spot for a few days to allow for some evaporation but if very runny, re-boil rapidly.
  • Too stiff? Probably overcooked or too much pectin added. Use it as a filling or in a sauce.
  • Bland taste? Could be from using poorly flavoured or overripe fruit, too short a cooking time or boiling too slowly or for too long, or too much sugar. While still hot, add further flavouring such as lemon juice, liqueur or sweet spices, such as cinnamon or nutmeg.
  • Crystallised jam? The sugar was not totally dissolved before the jam was brought to a rapid boil.
  • Separation occurs in the jar? The fruit for the jam could have been under ripened or undercooked. Allow the jam to cool for 15 to 20 minutes before pouring into jars. Stir gently before sealing.
  • Mould on top of jam? Jam has fermented. It was undercooked, had too little sugar, was poorly sealed or was sealed when neither hot nor cold, or was stored in a warm, damp area. This jam must be discarded. 

10 things to do with jam
Apricot jam
Minced apricot jam
Fresh apricot jam
Grape and walnut jam
Kumquat jam
Microwave apricot jam
Onion jam
Rose petal jam
Plum or nectarine jam
Grape jam


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