How To Make Jam
Good news! Jam is very simple to make. Most recipes involve:
- 50% fruit by weight
- 50% sugar by weight
- Pectin (a plant fibre that helps the jam to set)
- Fruit acid (for flavour, and to help with setting)
With small differences depending on the sweetness of the fruit, and how much pectin it naturally contains.
What Is Jam?
Jam has been made for centuries on different continents, by different peoples, using different fruit. Jam is a delicacy to be enjoyed, but the jam making process retains a high percentage of the vitamins and nutrients contained in fruit. In summary, jam is jammed full of goodness, and is a preserve that preserves the goodness of fruit. It is also full of calories, but the high sugar content plays an important role in allowing the jam to keep for many months.
The cultural diversity means there is no one universal definition of jam, 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 using the whole fruit, chopped up coarsely with small pieces often visible in the final jam (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 in a smooth paste, or jelly, and is made from pulped or blended fresh fruit.
Made from the juice of fruit, often because the fruit has a high seed or skin content, for example redcurrants, white currants, and blackcurrants. The juice is extracted by straining or pressing the fruit to separate the juice from the skin and seeds, that if left in the jam would make it chewy to eat.
A term that includes jam, marmalade, jelly, and chutneys, and made from fresh (not dried) ingredients.
Very similar to preserves. The naming difference may relate to using some dried fruit or nuts in the ingredients.
Pectin In Jam Making
Pectin is a naturally occurring carbohydrate found in plant cells. In jam making, it is important to help the jam thicken and set. Without pectin, a jam is runny and does not hold its shape.
There are three sources of pectin:
- Using fruit naturally high in pectin
- For fruit with low pectin content, adding extra peel or skin of fruit high in pectin
- Adding commercial pectin, either as a supplement or pre-mixed into sugar (sometimes known as jam sugar)
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 keeping a small box of powdered pectin in your kitchen cupboard.
Shown below are relative pectin levels of different fruit. Those marked high will not need extra pectin to make jam. Even for fruit high in pectin, it is best to use slightly underripe 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 added 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
These fruit contain moderate amounts of pectin. To achieve a good set, avoid using overripe fruit. Adding a little extra pectin can make setting more reliable.
Low Pectin Fruits
Use added pectin when making jam with these fruit, or add some high pectin fruit to your jam recipe.
- Apples (dessert)
- Cherries (Sweet)
Fruit acid adds flavour to jams, but is often used alongside pectin to help a jam to set. Lemon or lime juice are good sources of fruit acid.
Adding fruit acid is particularly useful when using ripe fruit, or fruit low in fruit acid such as strawberries, raspberries, and blackberries. If adding lemon or lime juice, the juice of one fruit 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 ingredients (like pectin and lemon juice) according to the fruit used, to achieve the ideal consistency.
Nearly all jams follow the process described below, but if you have a bread maker with a jam setting, you may like to see this page on how to make jam in a bread maker.
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 clean, with the stalks and husks removed, insect and bug free, and chopped coarsely.
2. Prepare The Jars And Lids
Many people re-use old jars and lids. All should be cleaned thoroughly in hot soapy water and rinsed. Buying new jam jars can help secure an air tight seal, which is important for the jam to store well. See jam jars on Amazon UK.
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 set at between 100 °C to 120 °C. If the jam is not ready, 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 added to a large flat bottom pan and placed over a medium heat. Some recipes add water to the pan, which when boiling, helps the fruit fall apart faster. This 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 jam can be removed carefully with a spoon or similar implement.
A large flat bottom pan helps the jam cook evenly, and is especially useful when making jam in large batches. See specialist jam pans on Amazon UK.
5. For Currants – Strain (Optional Step)
Blackcurrants, redcurrants, and white currants contain a lot of skin and pips relative to the amount of juice they contain. Straining the cooked fruit through a sieve, or muslin, separates the juice from the skin and seeds (which are discarded). The collected juice is used to make the jam (actually a jelly). See muslin on Amazon UK.
6. Add Sugar / Pectin & Cook Further
Combine all the sugar and any extra 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. Testing 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 105 °C. See jam thermometers on Amazon UK.
Without a jam thermometer, it can be tricky to know when the jam has cooked sufficiently to set, as the jam sets when it cools down. An experienced cook can tell by the consistency of the mixture, but other indicators are:
- If the jam falls off a spoon in blobs (rather than dripping)
- A cold plate test
Prior to cooking, put a small plate in a freezer drawer. At the end of the cooking time, spoon a small amount of jam onto the cold plate. Wait for 30 seconds, and then use a finger or spoon to spread the jam across the plate. If the jam holds it shape, and wrinkles, it is ready to go into jars. Otherwise, the fruit mixture will need to simmer for a little longer.
8. Decanting Into Jars
As soon as the jam is ready, it should be decanted into the sterilised jars, leaving an air gap of around 1.5 cm at the top of the jar. Ensure the jam jar screw threads and jam tops are completely free of jam. Using a large spoon, or ladle, to transfer the jam can be a messy job. Any spilled jam can be wiped away using clean kitchen paper.
A jam funnel is easier to use and keeps the jars cleaner, by helping to prevent jam falling onto the rim, screw thread, and side of the jars. See jam funnels on Amazon UK.
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 prevents the lids from being tightened fully.
9. Achieving An Air Tight Seal
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, and is complete when the jam is cold.
The popping sound, and lid finger test, demonstrates an air tight seal. Test by pushing down the top centre of a lid with a finger. It should not be possible to push the lid further down, nor should the lid spring back up. 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 mould or strange smells). Jams without an air tight seal should be stored in the fridge and eaten within a month.
You may like to see this video on boiling filled jam jars to secure an air tight seal. This additional step, sometimes called 'canning', makes achieving an air tight seal easier.
After all the hard work making your jam, you may want to show it off, or even give some jars away as gifts to friends and family. See jam jar covers and labels on Amazon UK.
Jam Making Equipment
Below is a list of jam making equipment. Rather than buying new equipment, it is often possible to reuse what you have at home, or find alternative ways of doing things. Buying specialist jam making equipment can make the process easier, less messy, and help improve hygiene (especially when filling hot jam jars).
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 specialist jam pan has a wide base, high sides, and easy handles to help pour the mixture into a jam funnel.
Weighing the fruit and sugar accurately helps the jam to set 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 accurately measures the temperature of jam – helping to determine the setting point (when the jam has reached the correct consistency and is ready for jarring).
Muslin pouches are used to add pectin containing ingredients like apple, lemon, and orange peel to the fruit mixture during cooking, before removing from the jam 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 is used to remove skin, pips, and seed during the cooking process. The mixture may need compressing with a spoon to extract as much juice as possible.
A jam funnel is a useful tool to make jam jar filling easier and less messy.
A food mill can be used to grind fruit into small pieces. It is especially useful for fruit with relatively thick skin and large pips, and helps retain vitamins and nutrients in the jam.
Once the jam jars are filled and sealed, a cooling rack helps speed up the cooling process.
Jam Jar Tongs
Sterilising jars requires the jars to be very hot, and the jars need to be filled when hot. Tongs are an excellent way of moving hot jam jars.
Lid Magnet For Moving Jam Jar Lids
After boiling lids to sterilise them, the jam jar lids need to be lifted out of boiling water and placed onto the top of jam jars to screw them on. A lid magnet is ideal for this, avoiding the need to touch the lids to transfer them, which reduces the risk of burning hands and fingers, and helps keep the lids clean.
A timer is very useful to follow cooking times. This is particularly important in jam making to ensure a good set.
See all jam making equipment on Amazon UK.