How to Make Jam

A traditional skill that was once essential to keep the family in fruit through the winter months, jam making can be a source of great pleasure. If you are not sure how to make jam or need some tips to hone your skills read on and get to grips with making your own tasty and fruit-filled jams, jellies and conserves. 

Basic science of jam (and jelly) setting

To make good jam, you need to balance flavour, consistency and food hygiene knowledge to preserve the jam safely. An understanding of the basic science behind jam making really helps you to make great jam. The techniques for jam are very easy to learn.

See also
With this complete step-by-step guide on how to make jam at home successfully
Secrets of small batch preserves that will help make you an expert in jam making!
All you need is 30 minutes to make this small batch blackberry jam recipe
How to sterilize jars for preserving for short and long term shelf stable preserves
Get ready to make this three ingredient jam that has no pectin and comes together fast rhubarb jam recipe

Here I am going to cover everything you need to know and understand, in order to make batch after batch of delicious jams and jellies that set perfectly every time and preserve those flavours for months or years after the summer has faded.

Pectin

Pectin is the gelling agent that gives jam and jelly its jammy consistency and makes it set.

Without pectin, jam would just be thick fruit syrup that would never set properly, no matter how long you boil it for.

For a successful jam you need either fruit that is already high in pectin, or to add pectin from fruit such as lemons, or to use commercial pectin. Pectin is available as a powder or liquid, or mixed into sugar sold as jam sugar.

Most recipes will have the correct amount of pectin, but if you are not working from a recipe or want to check the levels of pectin in your fruit, you can read my post on how to test for pectin. You will also find a guide to which commonly used fruits are high or low in pectin.

Sugar

Sugar is crucial in jam making, and although many of us are trying to cut down, it is important not to reduce the quantity of sugar in a recipe. There are three reasons why you cannot reduce the proportion of sugar:

First – The sugar binds to water in the jam, which frees the pectin molecules to bind to each other and set the jam.

Secondly – Sugar acts as the preservative in jam, inhibiting microbial growth. If you don’t use enough sugar, your jam can spoil and could result in serious food poisoning. Correctly made, jam can last safely for many years.

Thirdly – It tastes great and enhances the flavour of the fruit.

In short, if you are worried about the sugar, make the jam correctly and just eat a little less of the jam.

In jam making, the flavour of the sugar takes second place to that of the fruit and you do not want the toffee flavours of dark and golden sugars.

Use granulated refined white sugar, preserving sugar (white sugar with larger crystals, which helps to avoid too much froth and helps the set), or jam sugar, which is granulated sugar with added pectin.

It will make no difference to your jam whether your sugar is comes from sugar beet or sugar cane. After all that refining, there is no chemical difference between the two. Don’t worry about it!

Acidity

A little acidity is the final building block for good jam. You need a little acidity (i.e. a PH of less than 7) to help the pectin molecules bind to each other and set the jam. This is why most jam recipes have added lemon juice, as few fruits are naturally acidic enough.

Lemon also contains pectin, so don’t skip the lemon juice, especially if you are working with low pectin fruit.

Jam vs jelly

Beyond the Basics: jam vs jelly (and preserves, conserves and curds)

We all know what jam is; whole fruit or fruit chunks in a sweet jelly. Leave out the pieces of fruit, and you have jelly, made by straining the juice from the cooked fruit through a jelly bag or equivalent. You then add the sugar and pectin, and gently simmer until you reach setting point.

And jam vs conserve

Definitions of a conserve vary. For some, it is a jam made with whole fruit or large pieces of fruit, or even whole fruit in syrup.

To me, a conserve is a preserve for which I macerate the cold, uncooked fruit in the sugar, allowing it to draw the liquid out, rather than cooking the fruit before adding the sugar.

The variation in the definitions makes more sense when you realise that the conserve method preserves the form of the fruit, rather than have the fruit turned soft and mushy.

Starting out – learning to make jam

I believe strongly that when you first start to make jam, you should work in small batches. It is much easier to stay in control and you don’t need a vast preserving pan. If you make a mistake, you have less to lose.

If you make small batches of three or four jars more frequently, you rack up practice hours in the techniques you need for good jam. This means you will quickly gain confidence, and be able to spot when the jam is ready.

When you preserve in modest quantities, you don’t have to spend hours preparing huge quantities of fruit, you don’t need dozens of empty jars at a time. Importantly, the preserving is a pleasure rather than a chore.

You also end up with a diverse range of different jams in your cupboards. You may begrudge a whole cupboard dedicated to rhubarb jam but not a cupboard full of various jams, jellies and chutneys.

I find that a few jars of three or four different fruits is far preferable to a huge glut of one type. Make that mistake and you may find yourself pressing it on friends, family, neighbours, the postman and everyone in the street!

In fact, I’m so keen on making jam in small batches, I have written a whole post on the advantages of small batch preserves. Read it and I’m sure you’ll be convinced.

The basics of jam making

Before you start, there are several points to consider. You need to find a recipe, of course, and you will find a basic jam recipe below.

You also need to choose good fruit, sterilize your jars and make sure that you will know when your jam is ready.

How to select the best produce for making jam

One of the great things about making your own jam is that you know exactly what is in each jar. This can go down to the level of selecting the individual fruit. Obviously it’s best to remove damaged fruit and any showing signs of mould, and wash fruit before you start cooking.

However, it’s also a good idea (and we are back to that all important pectin again), especially for fruits that have low levels of natural pectin, to include some fruit that’s under-ripe, as the pectin levels are higher than when the fruit is fully ripe.

Many popular jam and jelly flavours are a combination of high/low pectin fruit, such as the classic blackberry & apple jam.

How to sterilize jars

Beyond the basics: Read more on how to sterilize jars.

It is essential to pot your freshly made jam into jars that have been properly sterilized. You should do the same with any jug and jam funnel you plan to use. This will help keep the jam or jelly from going mouldy before you open it.

This may sound intimidating if you are new to preserving but don’t worry. You don’t need an autoclave or any specialist equipment to do this.

If you have a dishwasher and wash your jars on the hottest setting, then they’ll come out clean and sterile. They will need to dry before you fill them, however.

The other option is to heat them in the oven to about 100°C or so for about 15 minutes. This has the advantage that it takes much less time than the dishwasher. The jars will be hot and ready to fill with jam whenever you’re ready.

The oven method will not work with plastic jugs and funnels, so use boiling water or the dishwasher for these.

How to test jams and jellies for setting point

Beyond the basics: Read more on how to test jam for setting point

There are three methods you can use to test for setting point.

First, the wrinkle test. Before you start making the jam, place a couple of side plates in the freezer. Once the jam has been on a rolling boil for a few minutes, and you think that it might have reached the setting point, take one of the plates out.

Now drop a teaspoonful of the liquid onto one of your chilled plates. Leave the blob of jam to cool – I leave it for about 30 seconds. Then push the drop of jelly with your fingernail to see whether the jelly wrinkles ahead of your finger as you push.

If it does, your jelly or jam has reached the setting point.

Second, temperature. Watch the temperature of the boiling liquid. Keep boiling until it reaches 105°C – the setting point for jam. You can use a jam thermometer for this. They’re easily available and not expensive. I prefer the digital versions, which are accurate and easy to use.

Make sure the thermometer is well immersed, but not touching the bottom of the pan.

However temperature is only a guide. You need to check with another method.

Third, the flake test. Using a metal spoon, take a spoonful from the saucepan, and turn the spoon vertically so that the jelly runs out of the spoon. Unset jam will fall quickly and cleanly from the spoon. As it thickens, the jam will fall more slowly and a drop or two will hang from the end of the spoon.

When the jam has reached setting point, a flake of jelly will hang from the edge of the spoon and not fall back into the jam. I find the best way of using this system is to continually pick up and pour out spoonfuls of jam once it has been boiling for a few minutes.

How to fill jam jars

I find that it’s always best to use a jam funnel for transferring the jam to the jars. This helps to avoid mess and scalding hot splashes. If you are using a jug and funnel, these should be sterilized in advance.

First, take the jars out of the oven and stand them in a roasting tray, with the lids close to hand. This will catch any splashes. Although it is rare for modern jars to break with the heat of the jam, it can happen. If you do have a disaster it will be contained.

Now ladle your jam into a heatproof jug. Then pour the jam into the hot jars through a jam funnel.

Seal each jar as soon as it is full. Ideally you want to leave about half a centimetre clear from of top of the jar. Clear away any spills and turn the lid so that it is secure.

As the jam cools, the jam and the jars will shrink slightly, creating a void in the top of the jar that will cause the dimple in the lid to pop into the sealed position.

How to test the jar is sealed

If the top hasn’t popped when you come to put your jam away, you may find you can pop the dimple down by hand. If it stays put, the jar is sealed, and the jam will store nicely.

Should you have one jar that refuses to seal, keep it in the fridge and start eating it now.

How about freezer jam?

Freezer jam is very common in North America but more or less unknown here. It is very easy to make and has a really delicious fresh flavour. Rather than cooking the fruit, you allow it to steep in sugar and pectin for 24 hours or so until the pectin has set.

Because the sugar levels are much lower than in cooked jam, freezer jam doesn’t benefit from the preserving effects of sugar. It therefore has to be kept in the freezer (hence the name). It is best eaten quickly, only lasting for a few months.

Do I need to water bath? Pressure can jam/jelly

Here in the UK, most recipes don’t require any processing once the jam has been sealed in jars. The combination of high sugar levels in jam, together with high temperatures results in a product that will keep.

In the USA, however, the Department of Agriculture via the National Center for Home Food Preservation, recommends that jars of jam are further sterilized in a water bath after filling. To do this you submerge the jars in a water bath, and boil for 10 minutes.

You might consider using this belt-and-braces approach if you are particularly concerned about food safety. You can find more details here. Having said that, the general consensus in the UK is that the traditional method is perfectly safe.

A basic jam recipe

Having considered all of these factors, it’s time to start making jam! Below, you will find a very simple jam recipe that’s great for beginners. You can use fresh or frozen fruit. If you use frozen, the recipe can be made at any time of the year, without any peeling or top-and-tailing.

More jam recipes

If you are ready to expand your jam-making experience, why not try one of these recipes?

• Blackberry and apple jam, a traditional combination that makes the most of the late summer harvest.
• Rhubarb jam, pink and pretty and so easy to make.
• Nectarine jam preserves the flavours of high summer for the whole year.
• And all my easy jam and jelly recipes.