I recently taught a jam making day at Denman College and at the beginning of the day I asked a group of eleven women what they hoped to learn. The replies followed a familiar pattern of frequently asked questions covering the selection of fruit, when to add water, types of sugar, how to test for a set and how to jar up the finished jam. Perhaps the key question was “what is the best jam making fruit”.


Some fruits make better jam than others and the best ones are high in pectin which is found in the walls of fruit and in the cores and stones of hard and stone fruit. Fruits that are low or medium in pectin can be combined with high-pectin fruits for jam. Low pectin strawberries and blackberries are often combined with high pectin cooking apples. A Tutti Frutti Jam has a mixture of red and blackcurrants ( high pectin), raspberries ( medium pectin) and strawberries ( low pectin). The riper the fruit, the lower pectin as it is attacked by enzymes that are activated during ripening.




Black and Red Currants

Cooking Apples



Plums ( some varieties)


Apricots (fresh).













Fruits that break down and soften with gentle simmering, for example raspberries do not need added water. Fruit with skins, gooseberries, black and red currants, plums, damsons, cooking apples and quince must be cooked in water before the sugar is added to the pan. If the skins are not softened the jam will be chewy.


Different recipes for jam making recommend a range of sugars, frequently confusing jam makers.

Jam Sugar

This sugar has added pectin, often marketed as a sugar for making jam with low pectin fruit, although this year I have seen recipes using it with all types of fruit. It’s easy to over-set jam using this sugar and create a firm (rubbery) consistency.
Price £2.10 per kg

Preserving Sugar

Marketed as a sugar with large crystals, an aid to dissolving and avoiding burnt jam.
Price £2.10 per kg

Granulated Sugar

Price 60-70p per 1kg
There are two types of granulated sugar, cane sugar and beet sugar. Having made jam with both I prefer cane for colour, consistency and flavour in the end product.

Setting point

Prolonged boiling to a setting point darkens the jam, weakens the flavour and frustrates the jam maker. Although it is tempting to make a large batch of jam, smaller batches made with 1-1.4kg fruit should set in matter of minutes producing bright coloured jams with balanced flavours.

Plate test

The plate test uses a chilled plate and a teaspoon of the jam, removed from the pan. If a skin forms on the surface of the jam and a wrinkle forms when pushed gently with a finger, it should set.

Temperature test

I sometimes use a digital thermometer to check the jam has reached 104.5C ( 220F) but it is not my preferred method of looking and listening to what is going on inside the pan.

Flake test

The advantage of this test is that the pan does not have to be taken off the heat or the jam maker distracted by the reading on a thermometer. I take a spoonful of the jam out of the pan, hold the spoon over the pan and turn it sideways. As the jam slides down, it should suspend on the side of the spoon. When I see this I know setting point has been reached. As the jam rests for a few minutes off the heat, a skin starts to form and if I push a spoon gently through the surface I see a wrinkle forming, another indication the jam is ready to be poured into jars.

Jarring up

After 25 years of judging and teaching jam, knowing how to fill and seal a jar remains misunderstood, by many jam makers, not helped by conflicting advice in books, online and in competition schedules. The best way is to use a clean, warm glass jam jar and a new screw top lid. Fill the jar to the brim then immediately seal it with a new lid. As the jam cools and sets, a vacuum is created between the surface of the jam and the underside of the lid. A well sealed jar will ” pop” when opened. Glass jars and lids are more easy to buy than 25 years ago. By all means use re-cycled jars but not lids as they don’t always seal jars and might cause spoilage.

Successful jam making is about following a few simple rules and a reliable recipe. Follow the links below to jam recipes in my books.



First Preserves recipe books
Bottle Company South

How to make Raspberry Jam

jam making

jam making

jam making

jam making flake test

jam making