Fudge is one of those really classic homemade sweets that we made often as children. The ingredients were cheap and, apart from the potential for full body burns, it is simple enough to make that children can easily master it.
The sweet science
Sweets are made boiling water and sugar together with variations on the theme. For example marshmallows involve adding the hot sugar syrup to beaten egg whites, and fudge involves the addition of cream and butter, but the science of the sugar and water remains the same.
Back to basics
When sugar dissolves in water there should be no large visible crystals of sugar. As the mixture is heated water evaporates from the pot and remaining in the pot is all the sugar and a slowly reducing quantity of water. The longer the pot boils the higher the temperature of the mixture will become, and the sugar syrup will slowly change its properties eventually turning to caramel and then to a black burnt mess. These stages correspond to different temperatures and can be measured using the cold water test or a sugar thermometer.
Cold water test
Start with a glass of cold water, and drop a drop of the sugar mixture into the water. Leave it for a few seconds then test the sugar droplet. See the table below for descriptions of each stage and corresponding temperatures
Using a thermometer is a far more accurate method for testing the stages of the sugar syrup. For Fudge we want soft ball stage or 112 – 115 degrees C
Full list of stages and temperatures
- Thread (106-112 degrees C) The syrup drips from a spoon, and forms thin threads in water
- Soft ball (112-115 degrees C) The syrup easily forms a ball while in the cold water, but flattens once removed
- Firm ball (116-120 degrees C) The syrup is formed into a stable ball, but loses its round shape once pressed
- Hard ball (122-130 degrees C) The syrup holds its ball shape when pressed, but remains sticky
- Soft crack (132-143 degrees C) The syrup will form firm but pliable threads
- Hard crack (146-155 degrees C) The syrup forms brittle threads and easily cracks and snaps
- Caramel (160-182 degrees C) The sugar syrup will turn golden brown and have a fragrant caramel smell.
Super saturated solutions and crystal size
As the moisture evaporates from the pot the solution becomes supersaturated, and the sugar crystals don’t need much encouragement to come out of solution and form back into crystals. If there is a single undissolved crystal present in the syrup this will act as a seed crystal for the crystals to form around and as the mixture cools large grainy crystals will appear. In the case of fudge, the mixture is beaten with a wooden spoon as it cools, before pouring into tray to set, causing the crystals to start forming but preventing the crystals becoming too large. Make sure you pour it out before it starts to set in the pot so that you can get a perfect flat surface. The texture of the final product should be smooth but have a slightly crystalline appearance.
Colour and catching
As the fudge mixture is boiled, the colour will darken, depending on the recipe the final colour may vary from pale golden brown to nut brown. Do not rely on colour alone to know if your fudge is cooked. As the fudge nears the end of its cooking time it has the tendency to stick at the bottom of the pot resulting in little brown freckles. Stir constantly at this stage to prevent that.
Fudge can be made very successfully in the microwave, choose a recipe that is specified as a microwave method, and be vigilant about stirring every 60 seconds, it can easily boil over and make a frustrating mess.
Cut your squares once the fudge has set but is still warm, this will ensure an attractive finish.
TOP TIP: Slice along the halfway mark of the tin then halve each side creating quarters and then eighths and so on until you have a nice width, then repeat the process in the other direction, that should ensure even sized squares without having to measure them.
Variations and volatile flavourants
Jazz up your fudge by adding nuts, dried fruits, sweets or crushed biscuits. Flavour them with any essences or extracts, a tiny bit of coffee, zest, liqueur or spices. Many flavour compounds are volatile, meaning they evaporate easily, so try adding the flavours at the end of the cooking process.
Fudge not setting?
If your fudge is not setting it could mean that it wasn’t cooked long enough, or that you did not beat it enough before pouring it out to cool. Scrape it all back into the pot and cook for a few more minutes, then make sure you beat until it starts to set around the edges before pouring it out. Any failed batches turn into butterscotch sauce by boiling in a little cream or crumble and serve over ice-cream.
Cleaning the pot
TOP TIP: for easy clean up, pour water into the pot and place it back on the heat. In a few minutes the sugar should have dissolved and the pot can simply be rinsed.
Rules for using a sugar thermometer:
Place a small pot of hot water on a nearby burner on the stove and keep it simmering throughout the process. Place your sugar thermometer in the pot of simmering water. When you want to measure the temperature of the mixture, remove the thermometer from the hot water and place in the sugar mixture. The thermometer can be clipped to the side of the pot, but make sure that the bulb of the thermometer is always dipped well into the mixture to prevent false readings. When you are finished with the thermometer place it back into the simmering water, this prevents the thermometers cracking as a result of heat shock.
Rules for dissolving the sugar:
Make sure that the sugar is completely dissolved before bringing to the boil. Warm the mixture over a low heat and stir constantly until the sugar has dissolved. Keep a bowl of fresh water and a brush near at hand, if any crystals become lodged on the side of your pot, brush them down into the mixture with your brush and a little fresh water. Once all the crystals are dissolved, then and only then, can you increase the heat and bring the mixture to the boil.
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- Julie Donald