How To Make Jam
Good news! Jam is very simple to make. Most recipes involve:
- 50% fruit by weight
- 50% sugar by weight
- Pectin (only required for fruit naturally low in this plant fibre)
- Fruit acid (optional – see below)
With small variations on the proportions according to taste and the natural sweetness of the fruit.
Read on for the full guide, or jump to:
What Is Jam?
Jam has been made for centuries on difference continents, by different peoples, using different ingredients.
This cultural diversity means there is no one universal definition, especially when it comes to naming different types of conserves and preserves.
My favourite set of descriptions is as follows:
Made from soft fruit, typically with the fruit chopped up coarsely and recognisable when spread (ie not blended to a paste or a clear jelly).
Made from citrus fruit like oranges, limes, and quince. Marmalades may have small chunks (bits) of fruit contained with a smooth paste or jelly made from pulped or blended fruit fresh.
Made from the juice of fruit, often because it is difficult to remove the pips or peel from the fruit itself, and it is desirable to do so . Think redcurrants, whitecurrants, and blackcurrants.
Like jam, marmalade, and jelly (plus chutneys) – made from fresh (not dried) ingredients.
Very similar to preserves. Naming difference may relate to using some dried fruit or nuts in the ingredients.
Pectin is a naturally occurring carbohydrate found in plant cells. It is important in jam making as it helps the jam thicken (or set). Without pectin, a jam can be soggy and runny.
For the jam maker, there are three choices:
- Use fruit naturally high in pectin
- If using fruit low in pectin, add an extra fruit containing pectin (ie peel or skin)
- Use commercial pectin
Using commercial pectin is the convenient alternative to option 2, as commercial pectin is often derived from fruit naturally high in pectin. Not all supermarkets stock pectin, and those that do may be sold out during jam making season. For convenience, it may be worth keep a small box of powdered pectin in your kitchen cupboard.
Shown below are relative pectin levels of different fruits – those marked high will not need extra pectin to make jam. Even for those fruit high in pectin, use slightly underripe fruit at at the expense of overripe fruit, as underripe fruit has higher pectin levels. For some fruit, like raspberries and tayberries, that naturally contain middling amounts of pectin, there are recipes that use added pectin and ones without.
In general, recipes that do not use pectin are lower in sugar and have a more fruity flavour (at the risk of a more runny jam). Recipes with added pectin use more sugar as this helps the jam to set.
High Pectin Fruits
These fruits do not need extra pectin for the jam to set. Pectin levels are highest in the skin, pith, and seeds – and younger less ripe fruit.
- Apples (cooking & crab apples)
- Plums (not Italian)
Medium Pectin Fruits
Do not use overripe fruit. Consider using pectin to avoid a runny jam.
Low Pectin Fruits
Use added pectin when making jam with these fruits, or add some high pectin fruit to your jam recipe.
- Apples (dessert)
- Cherries (Sweet)
Fruit acid helps to add flavour to jams, but perhaps more importantly, works with pectin and sugar to help a jam set.
Consider adding lemon juice to recipes if you are using very ripe fruit, or fruit low in fruit acid such as strawberries, raspberries, and blackberries. If adding lemon juice, the juice of one lemon should be sufficient, equivalent to around 2 tablespoons or 30ml.
Jam Making Method
There is science to jam making. The science of precise amounts of ingredients combining and reacting with each other to create a perfectly set jam.
Unfortunately, jam making is never precise. Even the same fruit plant, bush, or tree will give fruit with different levels of sweetness, juiciness, and pectin levels depending upon the time of year and the weather. The good news is that jam will always taste delicious – even if it is not perfectly set. Some people think that shop bought jam is often too set and stiff.
The experienced jam maker acquires the skill of knowing how to adjust cooking times and added ingredients (like pectin and lemon juice) according to the consistency they prefer in their jam.
Nearly all jams follow the process described below:
1. Prepare The Fruit
This is an important and time consuming task. Only the best fruit at full ripeness, or just before, should be selected. The fruit needs to be prepared ready for eating, which means clean, with the stalks or husks removed, insect and bug free, and chopped coarsely.
2. Prepare The Jars And Lids
Many people re-use old jars and screw lids. All should be thoroughly cleaned in hot soapy water and rinsed.
3. Sterilise The Jars And Lids
It is important that the jars and lids are hot when being filled with the jam. This is to ensure they are sterile, but also to help create a good air tight seal when the lids are closed. I find the easiest way of sterilising the jars is to place them in an oven for 30 mins at 100 °C. If the jam is not ready after this time, the jars can be left in the oven where they will remain hot. The process for lids is even easier. Place them loose in a pan of boiling water for 5 minutes.
4. Cook The Fruit
The fruit (and fruit acid) should be placed in a large flat bottom pan and heated over a medium heat. This process releases the all important pectin, softens the fruit, and enables the mixture to be gently mashed. Actual simmering times vary per recipe, with some jams avoiding boiling altogether and others requiring simmering for 30 minutes or so. Any froth or foam that forms on the surface of the cooking fruit can be removed carefully with a spoon or similar implement.
5. For Currants – Strain (Optional Step)
Blackcurrants, redcurrants, and whitecurrants contain a lot of skin and pips for the amount of juice. Straining the cooked fruit through a sieve, or muslin, is an excellent way of removing the problem. The collected juice can then be used to make the jam (actually a jelly).
6. Add Sugar / Pectin & Cook Further
Combine all the sugar and any pectin with the hot cooked fruit. Return the mixture to a vigorous boil and simmer for the time indicated in the recipe. Stir constantly to avoid the fruit sticking to the pan.
7. Judging The Jam Is Ready For Setting
If you intend to make jam regularly, a jam thermometer can be a useful investment. This measures the temperature of the jam and will tell you when the jam is ready for jarring. The jam setting point is when the mixture reaches 105oC.
Without a jam thermometer, it can be tricky to know when the jam has cooked sufficiently to set, as you will only see the result once the jam has cooled down. Apart from following the exact cooking time, an experienced cook can also tell by the consistency of the mixture. If the jam falls off a spoon in blobs -rather than drips – it may be set. Alternatively, a useful trick is to chill a plate in the freezer or fridge. At the end of the cooking time a small amount of jam is placed on the cold plate. By using a finger or spoon, spread the jam across the plate, and if the jam skins at all it is ready to be jarred. Otherwise, the fruit mixture will need to simmer for a little longer.
As soon as the jam is ready it should be decanted into the prepared jars, leaving an air gap of around 1.5 cm before the top of the jar. The screw lids should be tightened immediately. Tea towels or kitchen gloves are extremely useful at this point as the jam, the jars, and the lids are all very hot. Any spills around the jar openings and threads should be completely removed with a clean cloth or tissue – to ensure nothing stops the lids being tightened all the way.
As the air trapped in the jam jars cools, the lids literally make a popping sound. This sound is made as the air pressure inside the jar forces the surface of the lids to be sucked downwards. This process usually takes a few minutes. When you push on the top centre of the lid with your finger, you should not be able to push the lid further down, nor should it spring back up. The popping sound or lid finger test demonstrates an air tight seal. Jars with an air tight seal can be stored in a cupboard for around a year (but check before eating that the seal is still good, and for any signs of mold or strange smells). Jams without an air tight seal should be stored in the fridge and eaten within a month.
After all the hard work making your jam, you may want to show it off, or even give some as gifts to friends and family.
Jam Making Equipment
See my selection of jam making equipment on Amazon UK.
There are many types and sizes of jam jars available, with different closing mechanisms. One of the easiest are the simple screw top lids. A typical recipe will make between 3 – 5 standard size jam jars.
A big steel saucepan with high sides is the ideal cooking vessel to make jam. Aluminium pans are not recommended as the acid in the fruit may react with the aluminium.
Weighing the fruit and sugar accurately can help considerably to ensure that the resulting jam sets to the right consistency.
A colander is an essential piece of equipment for washing the fruit prior to cooking.
A ladle is a fast way of serving the prepared jam into jam jars.
Wooden spoons are ideal for stirring the jam during the cooking process to ensure the fruit does not stick to the sides and bottom of the pan.
A masher helps break down the fruit during cooking, releasing the pectin and the juice before the sugar is added.
A jam thermometer enables you to accurately measure the temperature of jam – helping you determine the setting point (when the jam has reached the correct consistency and is ready for jarring).
A specialist jam pan has a wide base, high sides, and easy handles to help pour the mixture into a jam funnel.
Muslin pouches can be used to add pectin containing ingredients like apple, lemon, and orange peel to the fruit mixture during cooking, that can then be easily removed before jarring.
Muslin squares are ideal for straining the hot fruit mixture before the final stage of cooking (when the sugar is added). Straining creates a jelly rather than a jam, but is a good option for fruit like currants that contain thick skin and pips.
An alternative to straining, a sieve can also be used to remove skin, pips, and seed during the cooking process. The mixture may need compressing with a spoon to ensure as much juice as possible is extracted.
A jam funnel is a very useful tool, making jam jar filling much easier and less messy.
A food mill can be used to grind the fruit into very small chunks. Especially useful for fruit with skin and large pips.
Once the jam jars are filled and sealed, a cooling rack is useful to speed up the cooling process.
Jam Jar Tongs
Sterilising jars results in very hot jam jars, that need to be filled whilst hot. Tongs are an excellent way of moving hot jam jars.
A timer can be very useful to ensure that correct cooking times are followed. This is particularly important in jam making to ensure a good set.
See my selection of jam making equipment on Amazon UK.
White Currant Jam
White currant jam sets easily and tastes indulgently sweet. It is a great way of enjoying a bumper crop of white currants (or red currants & blackcurrants).
Strawberry Redcurrant Jam
Strawberries make delicious jam, but the challenge is that it can be difficult to set. Strawberry and redcurrant jam is the solution, as yummy redcurrants are high in jam setting pectin. A simple and delicious solution!
Compotes use significantly less sugar than jam and this helps the fruit flavours burst through. Tayberry compote is a favourite, but it is easy to substitute for more readily available fruit like raspberries or blackberries.