Mix the water, fruit pulp, and the remaining sugar in a stainless steel saucepan and start to boil.
When nearing the ‘end point’ the dry mix of pectin and sugar is added. (The pectin should not
be heated for longer than necessary because it will be broken down and then the jam will not
Jam should not be boiled for more than 12-15 minutes otherwise this can give rise to caramel
flavours, over-sweetness and discoloration, 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%, this is measured with a
refractometer. (In most countries the legal minimum sugar levels in jam, are 65% for jam in
hermetically sealed jars, and 68.5% for jam in non air tight containers). 70% gives a safety
factor. Jam with over 70% sugar can give problems during storage, as sugar will recrystallise out
into large chunks. The ‘end point’ is usually reached around 106-108°C (depending on
barometric pressure and height above sea level). When the jam has nearly reached this
temperature samples are taken and tested on a refractometer, the sample must be cooled before
being measured. This can be done by smearing on a cold dry plate or saucepan lid. All
implements used to take the sample must be dry otherwise the reading will be reduced. It is
important to stir the jam at all times otherwise burning will occur at the bottom of the saucepan,
causing off flavours and discoloration.
When the ‘end point’ has been reached the jam should be filled into jars which have been
cleaned and then steamed to sterilise them, and are still hot so that they 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 the jars are sealed. 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 not keep cooking in the jar, the water
level should be kept below the lid of the jars.
Jars, omnia lids, and labels
Cooking facilities, gas ring, electric ring, etc
Stainless steel saucepan
Thermometer in protective jacket
Stainless steel cutting knife and spoon
Wooden spoon for stirring
Steam generator (optional)