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Homemade Blackberry Jam

My Nan is the queen of jam. If you step into my Nan’s pantry the walls are lined with jam in jars of all sizes, jams of all colours, jams you just can’t seem to find in the shops. She’s got gooseberry jam, plum jam, blackcurrant jam, redcurrant jam, whitecurrant jam (I’m still unsure what this is exactly), proper thick-cut no nonsense marmalade, whiskey marmalade the list goes on and on, but my favourite, everyone’s favourite is her signature bramble jelly. Deep purple, smooth and viscous, so viscous you can almost cut it out of the jar. Not too sweet, not too sharp, perfect. It wouldn’t be an exaggeration to say that many memories of my Nan involve bubbling pots of jelly and bright purple fingers. My childhood friends will know that if you turn up at my grandparents’ house unfed before noon you will be   expected to eat a small mountain of toast and jam before you leave, going without breakfast is something my grandmother has never stood for. But nobody ever complained. When I used to bring three jars of bramble jelly back to university my housemates used to put in their requests for more the following term.

Because of this, I always took homemade jam for granted. It’s a known fact that my mum can’t stand shop-bought jam tarts because she grew up with the real deal. Buying jam, especially blackberry jam or bramble jelly, always felt a bit wrong to me, so I thought I’d try my hand at making it myself, hoping that I’d inherited and absorbed some of my grandmother’s unrivalled knowledge and skill over the years.


Whilst jam is actually pretty simple to make (if you know how). There are a few important tips and tricks that make the whole process run a little smoother.

  1. Pectin. Because of my Nan’s jam prowess, I was aware of pectin before I ever stepped into any school biology class or did a chemistry degree.  Pectin is a starchy sugar present in plant cells that helps gives them their structure. Fruits like apples, pears, oranges and lemons are particularly high in pectin, whereas many of the fruits typically used to make jam, like blackberries, raspberries, plums etc. are very low in pectin. Now this is a problem, because pectin is the gelling agent in jam, without it your jam won’t set. One way to get around this is to use a preserving sugar (or jam sugar) with added pectin, another way is to use lemon juice.
  2. Butter. Yes, butter in jam, not just under it on toast. When you boil your jam a foamy film or ‘scum’ will start to form on the top, this isn’t a problem but too much of it will affect the texture of your jam. This can be prevented by adding a knob of butter towards the end of the boiling time. (I didn’t even know I knew this until I realized I’d just done it… turns out a lifetime of jam exposure had an effect on me after all) The fat in the butter will breakdown the foam and leave you will a smooth, shiny textured jam. If you’re vegan you can always scoop the foam off with a spoon before pouring it into jars, this just takes a little longer.
  3. The setting point. The setting point is probably the most difficult bit of jam making, after all nobody wants a jam that hasn’t set. As I mentioned earlier, pectin is the gelling agent in your jam, it works by being dissolved above a certain temperature, interacting with water and sugar present in your jam mixture and then forming a webbed structure as it cools. It’s this webbed structure that prevents your jam being too runny. Now if you’ve got a sugar thermometer, this part is easy, because the setting point is about 105˚C. Once your jam has reached that temperature you can remove it from the heat and pour it into jars to set. If you’re like me and a bit old fashioned, you can use the cold plate test. Place a small plate or saucer in the fridge whilst you jam is boiling. Once boiled for 10-15 minutes remove the plate from the fridge a spoon a dollop of jam onto it, before returning to the fridge for a few minutes. Take the plat out of the fridge and tip it, if your jam slides slightly and begins to crinkle as it does so, your jam has reached the setting point, if it’s still runny then you need to return your saucepan to the heat and allow the mixture to boil for a few more minutes.
  4. Seeds and pips. Now I don’t mind pips in my jam, but if you would prefer a jelly rather than a jam, you can always strain the juice from the jam mix using a jelly bag or a muslin cloth. But be aware that this is extremely time consuming and will result in purple stained fingers.

So here it is, my recipe for blackberry jam, an homage to my grandmother’s bramble jelly (plus seeds). Finally, a jam recipe on The Jam Jar!

Makes two 350ml jars

  • 400g of ripe blackberries
  • 400g of sugar
  • Juice of 1 lemon
  • A knob of butter
  1. First sterilise your jars. The easiest way to do this is to wash the jars and lids in soapy water and then put through the dishwasher on a hot wash, or put them in the oven at 100˚C.
  2. Thoroughly wash the blackberries and place them in a large, heavy-bottom saucepan.
  3. Add the sugar and the lemon juice and gently heat whilst stirring until all the sugar is dissolved.
  4. Once the sugar is dissolved you can slowly bring the fruit up to the boil on a medium to low heat for 10-15 minutes. 
  5. Add a knob of butter to the saucepan and stir it across the surface of the boiling mixture to remove the foamy ‘scum’ forming at the top. 
  6. Remove your jam from the heat and check whether it has reached the setting point (using a sugar thermometer or the plate test mentioned above). 
  7. If the jam has reached the setting point, pour it into your still-warm sterilised jars and seal. Allow to cool before labelling and transferring to the fridge for at least 24 hours before opening. 

One thought on “Homemade Blackberry Jam

  1. My one and only attempt at jam resulted in the stuff resembling and feeling like a boiled sweet, I threw the failed concoction and the jar in the bin; once cooled it wouldn’t come out of the jar! However I have hope with your step by step guide with timings. 🙂

    Liked by 1 person

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