It wouldn’t be Christmas without the smell of freshly baked gingerbread wafting through the house. With a blend of warming spices and rich molasses, it is a must-have treat for a winter’s day. And as a child, it was always gingerbread that I would leave out for Santa each Christmas eve. In fact, I think gingerbread might be my favourite biscuit – providing it has that perfect balance of crunch and chew.
I like to think I know a thing or two about how to achieve that. I competed in the 2023 series of the The Great British Bake Off and made it to the final – and I even received that famously hard-to-obtain handshake from judge Paul Hollywood during biscuit week.
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My success is down to the careful application of science to the craft of baking. So allow me to share with you a handful of key insights you need to bake a really show-stopping gingerbread – and the science behind why they are so crucial. Since I am a chemist by trade, we will be eschewing the traditional gingerbread house and instead assembling our biscuits into a freestanding Christmas “chemistree”. My mouth is watering already.
As with all biscuits, the first step is to prepare our dry ingredients. We need flour, sugar, spices and bicarbonate of soda (see “Ingredients and method”, right), each with important roles to play. The flour serves as a binding agent and helps form the structure of our biscuit, while the sugar will caramelise for sweetness, colour and texture.
The flavour of gingerbread comes from the blend of spices, with ginger and cinnamon leading the way. Their pungent fragrance is the result of volatile organic, or carbon-based, molecules, which rise into the nose and activate our olfactory receptors. Flavour compounds in ginger include gingerol and zingiberene, with cinnamaldehyde central to the aroma of cinnamon. They are all individually wonderful, but the magic of gingerbread stems from how these molecules come together. In the heat of the oven, these flavour molecules are also chemically transformed to become even more appetising, as we will see.
My first key tip, though, is to always add sodium bicarbonate (sometimes called bicarbonate of soda or baking soda) to a gingerbread mix, as it will result in a more aerated structure. Sometimes, gingerbread can be tooth-breakingly hard – not something I personally enjoy. But sodium bicarbonate helps avoid that. With the chemical formula NaHCO3, it undergoes a decomposition reaction in the heat of the oven, producing sodium carbonate (Na2CO3,), water vapour and carbon dioxide. Both carbon dioxide and water can also be formed in an acid-base neutralisation reaction, since sodium bicarbonate is alkaline and will react with any acids, such as those found in brown sugar – yes, brown sugar is mildly acidic! The bubbles of gas help leaven the biscuit, giving a gingerbread that is light but has a perfect snap.
We can now begin to bring our gingerbread dough together with the addition of the wet ingredients. My second top tip is that you want just a weak network of gluten in your dough to ensure the right texture – but let’s unpack that.
Royal icing is a great glue for sticking your gingerbread together
During this stage, two flour proteins called gliadin and glutenin become hydrated and interact to form the protein complex we know as gluten. The more a dough is worked, the stronger this gluten network becomes, which, depending on the type of bake you are making, could be desirable or not. When making bread, we add copious amounts of liquid at the start and knead rigorously to develop an elastic gluten matrix, leading to a soft and springy loaf. For our gingerbread biscuits, however, we want to reduce that gluten build-up. So, always rub the butter into the flour mix before adding any liquid. Doing this coats the gliadin and glutenin in a layer of fat so that when the liquid ingredients are added, these proteins aren’t hydrated as easily. We do need some gluten, as it helps capture the air bubbles described earlier. But just knead the dough a little by hand – no electric mixers, please – so you have enough gluten but not too much.
Now for tip number three, which I strongly suggest you don’t skip: allow the dough to rest in the fridge. This pause gives the proteins the opportunity to absorb more moisture and gives the gluten network a chance to relax, such that the dough doesn’t shrink back when rolled out. Even more importantly, it firms up the dough to avoid the biscuits spreading in the oven. Because we are looking to create well-defined shapes from our gingerbread, this chilling stage, both before rolling out and again before entering the oven, is essential.
After cutting out your gingerbread – use your own biscuit cutters or try my rough template – it’s time to bake. Always arrange the biscuits on a metal baking sheet, since metal conducts heat efficiently and gives your biscuits a crisp underside. Plus, you want them to have a strong colour before you take them out of the oven to cool, as this will ensure a depth of flavour and a biscuit that sets dry and strong – the ideal material for a chemistree.
As I hinted earlier, during the bake, some of the flavours in gingerbread are changed, with the gingerol being converted into other compounds via various chemical reactions. A reverse aldol reaction transforms it into zingerone, while dehydration reactions can turn it into a class of compounds called shogaols. In the 1970s, researchers determined that shogaols are
The last step – and my favourite part – is to decorate your chemistree. The biscuits can be simply decorated with glacé icing, comprising icing sugar and water. Or try another scientific tip: use royal icing, which is made with the addition of egg white. The network of proteins from the albumin in egg whites provides added structure and stability for royal icing, allowing it to be piped onto biscuits with ease and to harden quickly. This makes it a great glue for sticking gingerbread panels together – otherwise you run the risk of your tree disintegrating. For a really vibrant finish, you could also divide your icing between a few small bowls and use add different food colourings.
I have just one more show-stopping suggestion for you. If you want to go the extra mile and produce a really exceptional gingerbread tree, you could make some baubles out of isomalt. This sugar substitute can be melted and poured into a gap in the biscuit and left to set into a transparent “window”. Isomalt is derived from regular sugar (sucrose) via an enzyme-catalysed rearrangement reaction to isomaltulose followed by a hydrogenation reaction. It is much less prone to crystallising than regular sugar and better resists humidity, giving it unique properties that are perfect for creating transparent, glass-like decorations.
Right, now get to the kitchen! You have all the chemistry know-how you need to make a seriously impressive gingerbread creation. You don’t have to stick to a tree – let your imagination run wild and show me what you make on X using the hashtag #chemistree. I can’t wait to see how you get on.
Ingredients and method
For the gingerbread:
● 275 g (2¼cups) plain flour
● 1.5 tsp ground ginger
● 1.5 tsp ground cinnamon
● 1 tsp mixed spice (or pumpkin pie spice)
● 1 tsp bicarbonate of soda (baking soda)
● 100 g (7 tbsp) unsalted butter
● 50 g (¼ cup) caster or granulated sugar
● 50 g (¼ cup) light brown sugar
● 1 medium egg
● 60 g (4 tbsp) golden syrup (or light molasses)
● 60 g (4 tbsp) black treacle (or dark molasses)
For the icing:
● 200 g (1⅔ cups) icing or powdered sugar
● 20 g (1.5 tbsp) pasteurised egg white (or meringue powder)
● 1-2 tsp lemon juice, if desired
● Food colourings, if desired
1. Sieve the flour, spices and bicarbonate of soda in a bowl.
2. Rub the butter into the flour mix using your fingertips, then stir in the sugars.
3. Add the egg, golden syrup and treacle to the bowl, then mix everything together using a spatula to form a dough.
4. Turn the dough out onto a floured work surface and knead lightly until smooth. Flatten the dough, wrap in cling film and put in the fridge for 30 minutes.
5. Roll out the gingerbread on a lightly floured surface to a 6-millimetre (¼-inch) thickness, with a piece of cling film on top of the dough to ensure a smooth surface. Remove the cling film, then cut out the shapes of the gingerbread (you can find a template at if you would like to use ours). Place the cut-outs on a baking sheet lined with parchment paper and chill in the fridge for 30 minutes. Meanwhile, preheat the oven to gas mark 4, or 180°C (350°F), or 160°C (320°F) for convection ovens.
6. Bake gingerbread biscuits in the oven for 14 to 16 minutes or until deep golden brown, then transfer to a wire rack to cool.
7. To make the royal icing, add the icing sugar, egg white and 1 tsp lemon juice to the bowl of a stand mixer and beat until smooth. Add additional lemon juice a few drops at a time until a suitable piping consistency is reached and colour the icing as you like using the food colourings.
8. Decorate your chemistree.
Science of baking
Watch a step-by-step guide to making the perfect gingerbread at
