Jam, jellies & marmalade
Practical Action
Jam recipes
The following recipes have all been tried and tested. You can vary the total amounts made and
substitute other fruits, but always need to use the same proportions of ingredients.
Watermelon jam
Ingredients
Water melon
Sugar
Ginger
Citric acid
Pectin
115kg
55kg
0.9kg
0.47kg
0.66kg
Selection and preparation of fruit
Choose fully ripe watermelons that have a soft red flesh. Watermelons contain little natural
pectin so pectin has to be added to ensure the jam will have a good set. Citric acid is also
needed to increase the acidity of the juice (to pH 2.5 - 3.45). The yield of usable fruit from the
whole fruit is approximately 43%.
Wash the fruit in clean water and discard any bad part of the fruit.
Remove the skin from the melon, cut the flesh into small pieces and remove the seeds. Mash the
pieces into a pulp and strain through a muslin cloth.
Method
Mix the pectin with a small portion of the sugar. This is necessary because pectin powder is very
difficult to dissolve in water as it clumps together. If it is still a problem to dissolve, grind the
sugar to a fine powder and then mix it with the pectin.
Mix the fruit juice, sugar, citric acid and green ginger in a stainless steel saucepan and start
boiling the mixture. Near the end of the boiling process add the pectin and sugar mix. (The pectin
should not be heated for longer than necessary because it will be broken down and then the jam
will not set).
Jam should not be boiled for more than 12-15 minutes as this can lead to the development of
caramel flavours, over sweetness and discolouration, apart from being a waste of energy. By
reducing the amount of water in the starting recipe the boiling time can be reduced. The 'end
point' is reached when the total soluble solids is up to 70%, which is measured with a
refractometer. In most countries the legal minimum sugar levels in jam, are 65% for jam in
hermetically sealed containers, and 68.5% for jam in non air tight containers. Jam with a final
sugar content of over 70% sugar will start to form crystals in the jam during storage. The 'end
point' is usually reached around 106-108°C (depending on barometric pressure and height above
sea level).
When the 'end point' has been reached the jam should be filled into clean sterilized jars which
have been cleaned and then steamed to sterilise them, and are still hot so that the jars do not
crack. The jars should be filled as quickly as possible so that the jam is not heated for longer than
necessary, or recontaminated because it has cooled down before being sealed in the jar.
The lip of the jar should be clean and dry (wipe with clean tissue paper) before placing the lid on
it. The filled jars can be placed in water to cool down the jam so that it does no keep cooking in
the jar, the water level should be kept below the lid of the jar. The gel formation takes place as
the temperature comes down to around 55°C, if the jam is moved when the gel is forming the gel
structure will be broken and the jam will not set.
10