This Is Jam Hot | Modern Jam Making With Thermapen And Mary Cadagon

One of my earliest memories is standing on a stool at the hob in my Nan’s kitchen, stirring a huge pot of bubbling fruit and sugar. I was about five years old and it felt that her jam making process took an eternity. Oh how things have changed! And leading the charge is Mary Cadagon, former food director of BBC Good Food magazine, 18 times cookbook author and jam guru. Armed with only her expertise and a SuperFast Thermapen, she was given the unenviable task of teaching a room full of journalists and bloggers the secrets of modern jam making.

So there we stood, around a table of incredible looking fruit, in the La Cucina Caldesi Cookery school in Marylebone listening to Mary share some of her skills. With the basics covered, we were all paired up to choose our ingredients and make our own jam. My partner for the session was the wonderful Sam from parenting website Up All Hours. We decided on a Moroccan inspired rose, ginger and strawberry jam with just a hint of crème de cassis (just because). There were some incredible combos being worked up – greengage and bay, strawberry and cardamon and fig and orange flower were just a few of the recipes being tried. This truly is modern jam making at its most creative.


Getting fruity

You might think that jam making is complicated, but it’s surprisingly simple and only requires a few ingredients. But the crucial part of the jam making process is to ensure that it sets to the correct temperature. With the help of the SuperFast Thermapen digital thermometer, that provides an accurate temperature reading in just three seconds – even an amateur can be confident that their jam has set to perfection.

We were surprised by just how simple the whole process was, especially with the help of Mary’s Master jam recipe, her Top 10 jammy tips (both listed below) and the Thermapen. The best thing about modern jam making is just how quick it is. From start to finish, from chopping fruit to potting jam, the whole process couldn’t have taken more than 45 minutes (and that was with plenty of chat). The final results were amazing too, even if I say so myself – great texture, beautiful colour and an incredible fragrant flavour. Now that I know what’s achievable, I’m definitely going to keep an eye for new ingredients and make some more interesting jams. Watch this space!


Mary’s Master jam recipe

Makes about 3 large or 6 small jars


  • 1kg fruit, see list below
  • Juice of 1 lemon
  • 750g preserving sugar or jam sugar depending on the fruit
  • Herbs, spices, flavourings, botanicals, knob of butter

1. Wash the jars in hot soapy water and either put in a roasting tin and sterilise in  the oven at 160C/fan 140C/gas 3 for 10 mins, or put upside down in the top of the dishwasher and run a hot wash without detergent. The jars need to be warm when filled so time this carefully. Put two saucers in the freezer.
2. Prepare your fruit by chopping into even sized pieces. Put in a large heavy based pan with the lemon juice and sugar. Add flavourings of your choice, tied up in a muslin bag if necessary. If you are adding liqueur this is stirred in at the end.
3. Heat the fruit and sugar gently, stirring until the sugar has dissolved, then increase the heat and bring to the boil. Keep the jam at a good boil, stirring, until setting point of 105 degrees celsius is reached on your Thermapen Mk 4. Or use the wrinkle test, see below..
4. Skim off any excess scum from the surface of the jam using a slotted spoon, then stir in a knob of butter to remove any residue.  Cool the jam for 10-15 mins, then stir to distribute the fruit evenly and  ladle into the warm jars, using a jam funnel if you have one. Add wax discs to the surface of the jam and screw on the lids. When cool add the label with the type of jam and date made.
5. Store your jam in a cool dry place.

Mary’s Top 10 tips for modern jam making

1. Choose the right sugar for your fruit. For high-pectin fruits, like apples, pears, plums and oranges, you’ll only need ordinary granulated sugar or preserving sugar which has quick dissolving crystals. For low-pectin fruits however, such as cherries, grapes and strawberries, you need to use proper jam sugar, which has added pectin. Using the appropriate sugar will not only ensure a better set, but it will cook more quickly to capture all the fruity flavour.
2. Use a wide pan with a thick base. Using the right kind of pan will help your jam cook more evenly, allowing more area for the mixture to bubble and evaporate. It’s crucial to continue stirring the jam while cooking it in order to stop it catching on the bottom of the pan. It can also be very helpful to use a jam funnel, which helps you get the jam into jars without spills.
3. Pick under-ripe fruit. It’s a misconception that you can use squishy, out of date fruit for making jam. Once fruit becomes over ripe, it loses much of the acid that is essential for making a great jam.
4. Cut the sugar. Traditional recipes use equal quantities of sugar and fruit but I have found you can afford to reduce the sugar to allow the fruity flavours to shine through. A rough guideline would be for every kilogram of fruit, you’d need 750 grams of sugar. Keeping the sugar down will also give you a softer set.
5. Cook in small batches. While cooking huge batches of your trademark flavoured jam may feel productive, nobody wants the inevitable, 20 jars of forgotten jam at the back of the cupboard. Cook your jam in small batches, maybe a few small jars at a time, experimenting with different flavours. This will ultimately make each batch feel that bit more special and you will feel freer to experiment with flavour combinations.


Feeling hot, hit, hot!

6. Invest in a good thermometer. Taking out the guesswork will make cooking jam so much easier. Getting your jam to the perfect temperature to set is crucial so it’s good to invest in an accurate, easy to use thermometer such as the SuperFast Thermapen® 4.
7. Pimp the flavour. There are a myriad of options and combinations when it comes to modern jam making. Loganberry with star anise. Rhubarb and ginger. White peach and raspberry. Rosemary, pepper. Cardamom; the list goes on. Using garden herbs, spices and whatever other flavours come to mind will give your jam that personal touch that separates it from anything you can find at the supermarket.
8. Use fruit in season for the best flavour. Keep your eye on the market stalls and go fruit picking to get the best fruit available. Hand picking the fruit that goes into your jam really adds to the whole feel-good experience.
9. Don’t forget the acid. Controlling pH levels by adding acid in the form of lemon juice is vital for getting your jam to set well in addition to preventing the jam from going off while in the jar.
10. Prepare the jars. Sterilising your jam jars is vital, either put them in the dishwasher on high heat with no detergent or rinse and put them in the oven at 160 degrees (gas mark 3) for ten minutes. Don’t forget to label your jars with the date and flavour for future reference. Make sure to cool your jam for 15 minutes before potting it to ensure the fruit is evenly distributed through the jar.

About SuperFast Thermapen
The SuperFast Thermapen® is made in Britain by ETI Ltd. The Thermapen 4, includes a patented 360° self-rotating display that can be used in any position, in either hand. The unit incorporates an intelligent backlit display sensing light levels, automatically turning the backlight on/off in varying light conditions. The motion-sensing sleep mode automatically turns the unit on/off when set down or picked up, maximising battery life. The Thermapen 4 case is waterproof and includes ‘Biomaster’ additive that reduces bacterial growth.

It can be used to perfect dishes of all varieties from jams and preserves, to breads, sauces, barbequed meats, tempered chocolate and confectionery. The Thermapen is competitively priced from £51.60 each inclusive of VAT, and available in a variety of colours direct from

For more information on Thermapen visit their website