Making jam is a simple process of gently simmering fruit, adding sugar and boiling briefly to setting point. Jam is the preserve I recommend to beginners, although without quality fruit, a balanced jam recipe with detailed instructions, the jam is unlikely to set with a gelled consistency, bright colour and true fruit flavour.


The best set jams are made from top quality, just ripe, high pectin and acid fruit. Ideal choices are black and red currants, cooking apples, damsons, and green gooseberries. Medium pectin fruit include raspberries, loganberries, tayberries, plums, and apricots. Poor setting fruit include strawberries, peaches, cherries, pears and rhubarb. If you want to make jam with low pectin fruit, either combine them with high pectin fruit, for example Blackberries with Apples or add pectin stock made from gooseberries or redcurrants.

Reducing the Volume

Before the sugar is added, fruit is simmered with or without water. Many jam recipes ignore this stage and dissolve the sugar into the fruit and boil it to setting point. Bypassing the simmering stage prevents the softening of the fruit, and the release of pectin into the pan. Fruit with firm skins- black currants, plums, damsons, greengages, gooseberries, quinces and apples must be cooked in water. Hard, chewy skins are unpleasant in jam. Soft fruit such as raspberries, loganberries and strawberries will soften in their own juices. The contents of the pan are normally reduced by a third. Fruit with firm skins may need up to 30 minutes, soft fruit varieties will collapse more easily in half the time. I make small batches of jam, 2.25kg is ideal as larger batches take longer to set and the flavour is weaker. Once the volume has been reduced the proportions of fruit, pectin and acid should be in harmony, ready to add the sugar.

Pectin Test

If you are uncertain it’s time to add the sugar, a pectin test may help. Remove 1 teaspoon of the liquid from the pan. Pour the liquid into a small glass or ramekin. Add 1 tablespoon of methylated spirit to the glass or ramekin and swirl the contents together. A jelly lump will form when plenty of pectin is present. If the pectin content is medium, the lump will look more like an amoeba. If there is too little pectin, the clot will be broken down into a number of small blobs.


For jam, I recommend granulated cane sugar as it gives a bright colour and an excellent set. Warm the sugar before adding it to the pan, this helps to keep an even temperature in the pan, and the sugar dissolves quickly. Products retailed as “Jam Sugar” can affect the colour and texture of jam, often a brighter colour and a firmer set, which can be helpful if you do not always achieve a set. Avoid sugar substitutes when making jam. Saccharine, a sweetening agent, will not form a gel so the jam will not keep. Reducing the amount of sugar in the jam recipe will mean a slacker ( not set) consistency and the jam will have a shorter shelf life.

The amount of sugar added will depend on the pectin content. Medium pectin fruit, raspberries and plums will set with equal quantities of sugar. High pectin fruit, such as black currants and damsons will set a higher proportion of sugar. For example, 1kg gooseberries or blackcurrants to 1.4kg sugar. For the jam to set, the end product should have a minimum total sugar content of 60% to ensure a shelf life of at least a year.

Testing for a set

I prefer to use the flake test, as the pan stays on the heat, the temperature does not fall, so no delay in getting to setting point. Dip a large spoon into the pan and scoop out a spoonful. Lift the spoon above the pan and turn it horizontally. Look for a drip of jam, then a flake of jam hanging on the side of the spoon, a visual example of the gel in the consistency. Other tests, for jam include a temperature test, when the jam reaches 104.5C, or a plate test. None of these tests are foolproof, without the correct proportions of fruit, sugar, acid and pectin.

Once the jam has cooled, and before potting it, I like to gently press the surface of the jam with the back of a metal spoon. If there is a resistance, it usually means the jam will set in the jars. Also, as I remove any scum, I look for a wrinkle on the surface of the jam, another sign of a set.

Boiling and Re-Boiling

Many recipes suggest long boiling times before testing for a set. When I make jam, the set is reached in under 10 minutes, the average 7 minutes. Prolonged boiling will make the jam go syrupy or stiff in the jar, rather than setting with a gelled consistency. Prolonged boiling converts the sugar to “invert sugar”. A second boil will not result in a set unless another ingredient is added ( usually a liquid pectin product). This might “set” the jam but it will compromise the true fruit flavour and change the texture. The longer the boil, the weaker the flavour and the colour of the jam changes from brilliance to darkness. With this in mind I was very concerned to read that a book published in August 2015, suggests boiling for 30 minutes. From my years of making and judging jam, successful jams are those made with recipes using traditional methods. If your jam does not set, all is not lost. Jam is an excellent ingredient in baking and some tried and tested recipes can be found in my ebook Jam: Make and Bake, available on Amazon Kindle stores worldwide. E.G.,

For a good set, choose a traditional jam recipe based on science.