Jam, jellies & marmalade
Practical Action
b) Use a sugar thermometer
This method is slightly less accurate, but is very useful at the small-scale. A solution of 68%
sugar boils at 105°C at sea level. When the boiling jam reaches this temperature, it is at its end
point.
After boiling for a few minutes, stir the jam and remove the pan from the heat. Dip the
thermometer into hot water and then into the jam. If the thermometer reads 104-105°C, the jam
is ready. If it is lower than this, return to the heat and continue to boil. Test the temperature
frequently as the jam soon reaches its end point.
Note: At higher altitudes the boiling point decreases and should be adjusted. The end point is
about 4.5-5°C above the boiling point of water at any altitude (see table 1 for estimates of the
boiling point of water at different altitudes). A sugar thermometer costs about US$10.
Altitude above sea level
Boiling point of End boiling point of
Ft m
water (°C)
jam (°C)
00
100
105
1000
305
99
104
2000
610
97.9
102.9
3000
915
96.9
101.9
4000
1220
95.8
100.8
5000
1525
94.8
99.8
6000
1830
93.7
98.7
Table 1. Boiling point of water and end point of jam at different altitudes
c) Use the drop test
This is the cheapest option, but is the least accurate of the methods. It is good enough for use at
the home level, for jam that will be used within a fairly short time. It is not recommended for
jams that are meant for sale as there is no guarantee of consistency from one batch of jam to
another.
After two minutes of rapid boiling, remove the pan from heat. Dip a clean wooden spoon into the
jam and hold it over the pan for 1 to 2 seconds. If the jam runs back freely, repeat the test every
two minutes until the jam looks like a heavy syrup. When a small lump of jam forms on the back
of the spoon and breaks away from the rest, the setting point has been reached.
Alternatively, you can drop the jam into a glass of cold water: Take a small drop of the boiled jam
on a spoon. Cool it slightly and drop into a glass of cold water. If the drop falls in a single piece
until it reaches the bottom of the glass the end point has been reached. If it disperses in the
water it requires boiling for longer.
d) Use the skin wrinkle test
This method is also cheap and about
as accurate as the drop test. You need
a cold plate or saucer. After two
minutes of rapid boiling, remove the
pan from heat. Dip a clean wooden
spoon into the jam and drip a small
amount of jam onto the cold plate
surface. Let it cool and then push the
lump of jam with your finger. If the
surface of the lump of jam wrinkles
when you push it, it is cooked.
You can always cook for a little longer, but you
cannot go back if you heat for too long. It is
better to take the jam off the heat too early and
then re-heat if it is too soft.
Test the jam at frequent intervals so you do not
miss the end point.
Remember to remove the pan of boiling jam from the heat source while you are doing these tests
as the jam will continue to cook and may become over-cooked.
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