Do you like caramel? I absolutely love it in practically any dessert I eat. It’s so sweet and gooey, and makes every treat so much better, but do you know the science behind it? Today I’ll be telling you the chemistry behind making caramel, because it’s not as easy as it may seem at first glance. Most people think that it’s a super simple reaction: add granulated sugar in a pot, add water, and heat it up to eventually form caramel. But what’s the science behind it?
Step 1: The sugar splits up into smaller pieces of sugar
Basically, table sugar (the sugar you get at the grocery store) is made up of these two compounds called “fructose” and “glucose”. When heated up, the table sugar (also known as sucrose) breaks up into these two compounds. This is called “hydrolysis”, and you can think of it as breaking 1 big Lego tower into two smaller ones (but submerged in water).
Step 2: The water eventually leaves and the sugar reacts
As we continue to heat up the sugar, the water molecules inside the sugar eventually start to evaporate (which is called “dehydration”). This allows the sugar molecules to stick and react with one another in more ways more effectively, and form other compounds such as “difructose-anahydride”. That’s just a fancy molecule that helps the plain sugar turn more golden and have a more complex flavour.
Step 3: Sugars break down
The sugars react even more with the heat. Basically, with more heat, sugar molecules break apart even more and increase the number of molecules that react with one another. They essentially rearrange and combine into bigger molecules. This is where the caramel color deepens from light golden to amber to dark brown. It’s also when the flavors start to get nutty, toasty, or even slightly bitter if you cook it too long.
Step 4: Fragmentation
At this point, the sugar molecules are under some serious heat pressure, which causes a process called “fragmentation”. So along with splitting into even smaller parts than before, there are 3 compounds that are further emphasized. Diacetyl: which gives it a buttery flavour; Furan: which adds a nutty flavour; and Maltol which gives it a toasty warm vibe (like Christmas).
Step 5: Polymerization
Yes, the name sounds complicated, but this final process is actually pretty simple and pretty important too. So in step 4 we talked about “fragmentation” where the sugar molecules broke up, but now some of those same molecules join up again. But instead of joining up to how they were before, they link in an entirely new way forming these 3 large brown molecules: Caramelan (C12H18O9) , Carmelen (C36H50O25), and Caramelin (C125H188O80). These molecules along with the other compounds mentioned in step 3 all make caramel so gooey, sweet, and delicious!
Now that you know the science behind caramel, stay tuned for more sweet facts just like this in the STEM section of the YAA blog.