How to make a toffee apple – The science of Caramelisation


Toffee ApplesBonfire night activity – Toffee Apples

Recipe:

Equipment – kitchen scales, measuring jug, large bowl, large saucepan, wooden spoon, teaspoon, tablespoon, wooden skewers, sugar thermometer or digital cooking thermometer, non-stick baking paper, small bowl of cold water.

Ingredients – boiling water, 8 apples of your favourite eating variety, 400g sugar, 100ml water, 4tbsp golden syrup, 1tsp cider vinegar (or any vinegar type apart from balsamic which tastes a bit too strong).

Method – put the apples in the bowl and cover with boiling water.  This will make sure the skins are clean and smooth so the toffee will stick.  You can give the apples a rub once the water has cooled enough.  Push the skewers into the apples at the stalk end.

Put the sugar and 100ml water into a large saucepan, stir and heat gently until the sugar dissolves.  Add the vinegar and golden syrup and heat more strongly.  There is no need to stir now.  Use your sugar thermometer carefully.  You need to heat the mixture until it gets to between 146⁰C – this might be labelled ‘hard crack’ on a sugar thermometer.

Be very, very careful with your toffee now because it will burn you if you get a drop on your skin.  To double check that it is ready, put a drop from your wooden spoon into the bowl of cold water.  If it is ready, the drop of toffee will go hard and brittle.

Turn off the heat but leave the pan on the stove so it does not cool too quickly.  Dip each apple into the toffee to cover it completely.  Put the apple on the baking paper to cool.  There may be a little drooping of the toffee while it cools but don’t worry – the toffee ‘skirts’ around the bottom will be very tasty!  Left-over toffee in the pan can be poured straight onto the baking paper and broken into toffee sweets when cold.

Science:

When making toffee, the sugar and the golden syrup make a very concentrated sugar solution.  As this is boiled, the water evaporates but the sugar remains in the saucepan.  The solution becomes more and more concentrated.  The point at which heating is stopped determines the texture of the resulting toffee.  If it is below about 146⁰C the toffee will be chewy because there is slightly more water in it.  Above 146⁰C it is much more crunchy because more water has been boiled off.  If the temperature is too high then the sugar will burn.  These temperatures are approximate because the exact mix of sucrose (sugar) and invert sugar (in golden syrup), other ingredients and even atmospheric pressure will affect the relationship between the temperature and the sugar concentration.  The cold water test will tell you if your toffee will be chewy or crunchy at that time.

Rapid cooling on the baking paper, without stirring, makes sugar crystals form throughout the toffee quickly.  These crystals will be tiny and give the toffee a smooth texture.  If the toffee is stirred as it cools, crystals start to form where the stirring happens and they have time to grow large.  If the toffee cools very slowly, large crystals have time to form too.  These large sugar crystals give the toffee a grainy texture.

Good luck with your toffee making, and make sure you clean your teeth thoroughly after eating!

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