Jam Session – tips for making homemade jam

fruit for jam

Plenty of fruit for jam!

I may have mentioned (just the once or twice) that I love to go fruit picking in the summer. It’s a fun and delicious way to spend a few hours and a great way to make sure the kids get their five a day! I usually go with the intention of picking fruit for jam and some for us to eat.

I didn’t really eat much jam before I started making it myself. With the exception of Bonne Maman, I didn’t really like shop-bought jam. Now I make so much that even though I give most of it away, I still feel obliged to eat it for breakfast every day. Luckily homemade jam makes a great gift.

homemade jam

A small selection of this year’s jam so far…

On our last fruit picking trip we picked raspberries, blackcurrants and redcurrants. Strawberries were in very short supply so we will be going back for those but the raspberries were virtually jumping into the punnets on their own.

The last few years I have brought apricots back from France but this year I managed to find some in Costco. And a friend gave me their plum crop to turn into jam as well.


Plums fresh from the tree

Jam is a relatively simple process: you cook your fruit until it is soft enough, then add sugar and boil it until it reaches setting point. Getting it right is slightly more difficult. I struggle with deciding when a jam is set enough as I prefer it soft set. It’s often quite tricky to decide if it has reached soft set: it’s much easier if you like it quite thick.

homemade jam

Blackcurrant, plum and raspberry jams

The plum jam is a little runny but doesn’t quite slide off toast, unlike some of last year’s apricot jam…

The process relies on the combination of pectin, acid and sugar. Sugar preserves the fruit. The pectin sets the jam and the acid helps extract the pectin. Different fruits have different amounts of acid and pectin and in general, the less ripe the fruit is, the more pectin it contains.

As a general rule, you use the same amount of sugar to fruit. So you can weigh your fruit and use the same amount of granulated sugar, which saves needing an exact weight of fruit each time you want to make jam. Some recipes will call for more sugar than fruit: for example, some blackcurrant jam recipes. I like it quite tart so keep the fruit to sugar ratio the same.

fruit for jam

Different fruits have different amounts of pectin, water and acid

Some fruits need the addition of water because they have a lower water content. Blackcurrants again often need a bit of extra water.

It is important to heat the fruit gently until the juices run and the fruit is soft before you add the sugar. If necessary mash it up a little as well. Once you add the sugar the fruit will not soften any further. And you could end up with blackberry jam where the blackberries run off the toast. It still tastes good, just doesn’t look as professional!

fruit for jam

Prepare your fruit before heating

Some fruits are naturally low in pectin and harder to make into decent jam. I still haven’t mastered strawberry jam. There is always the option of adding pectin and you can buy jam-making sugar which contains added pectin, or pectin in liquid or powder form. I have always resisted adding pectin as I (probably undeservedly) feel it is cheating but I think if I ever want to make proper strawberry jam I will need to.

What I do often add to help jams set is lemon juice. It adds acid which helps extract the pectin from the fruit and can make a real difference. It can also make the jam really clear and brightly coloured which is an added bonus.

Once you have added the sugar it is important to get the jam to a really fast boil as quickly as possible. It will need a stir every now and then to stop it burning. When I first started making jam, the recipe I used said not to stir it when it was boiling so I didn’t. It took me a full week and every cleaning product known to man to get every last burnt raspberry pip off the bottom of my jam pan. And it’s a big pan. But because the burnt bits stayed on the pan, the jam was fine.

I test for a set the old-fashioned way. I put a saucer or two into the fridge and drip a few drops of jam onto it to test. The saucer is cold and will cool the jam quickly. If it forms a crinkly skin when you push it with your finger it is ready, but let it cool a bit before you try. Otherwise let it continue to boil and try again in a minute or so.

When the jam is boiling it forms a scum which can be skimmed off with a flat slotted spoon. When the jam is ready turn off the heat and allow it to sit for a few minutes. Skim off as much as you can as if you leave it, the scum will be noticeable in the jars. Stirring in a small lump of butter also removes but I have only tried this once; partly because I feel it is cheating, and partly because I am afraid I might give it to someone with a dairy allergy by accident. I only used a very small amount and it definitely helped. Had I used more I’m sure the scum would have disappeared entirely.

jam making

Skim off the scum on the top of the jam

It is important to put the jam into sterile jars while it is still hot. If you are planning on making lots of jam keep all the glass jars you use and ask your friends for theirs: it’s much cheaper than buying them. Just remove the labels, dishwash them and put them away until you need them. If necessary you can buy new lids. Put the jars into a tray in the oven (without their lids) and turn the oven to about 180ºC. I often turn the oven off when it comes up to temperature and leave them there until about ten minutes before I need them.

The jam jars need to be hot or they will crack when the jam goes in. But if they are too hot they will start the jam boiling again – you will see it if it happens – and then the fruit can rise to the top. So it’s always a good idea to let both the jam and the jars cool a little before filling the jars.

plum jam

Plum jam cooling in jars

Some people use a ladle to fill the jars, some a Pyrex measuring jug to pour it in. I prefer to use a wide jam funnel that sits over the neck of the jar and pour it in as my jam pan has a pouring lip. Always be really careful to stand as far back as possible and wear oven gloves and an apron for this part. The jam often splashes and can be very dangerous. Put the lids on immediately and tighten using a tea towel or oven gloves and again when they have cooled down. You can also use wax discs to help keep any moisture out but I have found them to be unnecessary.

Label them when they are cold so that you know what they are and when you made them. Last year I didn’t label mine because I had planned to make proper labels. However it is very difficult to tell the difference between blackcurrant and blackberry jam without opening up the jar! My plan this year is to replace my scruffy labels when I give them to people…

And if you find the jam has not set properly when it is cold, you can put it back in the pan and boil it again until it reaches a proper set.

So hopefully some of the things I have learnt from making jam will be of use – do you have any tips for me?

blackberry jam

It will soon be time to make blackberry jam as well…

Categories: Fruit, Fruit picking, Jam making and Preserves

Tags: , , , , , , , , , , , , , , , ,

29 replies

  1. Such a well written and comprehensive post. My mom used to make jams with so many fruit…apples, guava jelly and guava cheese, mango…
    I make berry compotes or conserves, but use it up within 3-4 days usually. I’ve also heard that to set strawberry jam, boil it with a strip of lemon peel which you can discard later. Don’t know where I read of it, but I now use lemon peel even when I make strawberry or blueberry or orange curd. It sets it faster.

  2. You sound like a jam pro! I tried making fig jam once, but ended up with a compote instead. Tasty, but…not quite jam. Love that the raspberries were jumping into your buckets, what a great image!

  3. Oh my gosh! How cool! It would be great to make jam! Your jam looks great! 🙂

  4. Brilliant read! I’ve also fallen foul of the not labelling and then forgetting what is lurking in the jar. Putting the year on it also helps. The biggest thing that helped me with jam making was getting a probe thermometer – they are not cheap but can be used to make sure that lots of foods are properly cooked. Have you read the River Cottage Preserves book? That has loads of fantastic ideas for using up any fruit glut and makes jam, jelly and curd making so easy.

  5. Thanks for the great post! I have successfully made strawberry jam, strawberry and apple jam (with only half the sugar, still very sweet and tangy) and apricot jam, using the ‘confiture sugar’ – its so easy I don’t think of it as cheating 😉

    Today I have two huge bags of figs from a friend’s tree – going to make fig & onion chutney and fig jam – I just don’t have any jars!

    • I love figs, that sounds really good – and good luck with finding some jars! Thanks very much for taking the time to read and comment, I am definitely going to get some confiture sugar if I get some strawberries.


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