It’s not often that we delve into the science behind coffee, but there are a few interesting concepts that many of you would want to know.
For instance, what transforms green beans into the delicious, flavourful coffee that you love?
Coffee roasting is often hailed as an art. Developing the roast approach, knowing what sensory profiles it would result in, using creative decision-making - a roaster builds these skills with experience.
That said, the chemistry underlying it is what makes good coffee possible.
And that’s why today, you’ll read more about the Maillard reaction.
What Exactly is the Maillard Reaction?
The simplest way to understand the Maillard reaction is to think of it as the chemical changes that occur when reducing sugars and amino acids in the beans are exposed to heat.
The name is derived from French chemist Louis-Camille Maillard, who first described this in 1912.
This occurs towards the end of the drying phase. Once enough moisture has evaporated from the bean, the temperature rises within, and the bean starts to turn brown.
It is not to be mistaken for caramelisation, as that occurs when the sugars are broken down. The Maillard reaction involves both the sugars and the amino compounds.
This chemical process is not just important to coffee. You have experienced it in toasted marshmallows, baked cookies, and when your breakfast sandwich has that delightful crispy crust.
How it Shapes Flavour in the Cup
The reason your coffee tastes nutty, toasty or chocolatey has a lot to do with Maillard chemistry.
As the chemical reaction continues, new aromatic compounds that are responsible for capturing body, sweetness and depth in the cup are formed.
Some common tasting notes associated with Maillard development in coffee are:
-
Milk chocolate
-
Hazelnut
-
Biscuit
-
Toasted almond
-
Malt
-
Brown sugar
These flavours aren’t added to coffee. They are brought out through the transformation of compounds.
When the reaction isn’t well-developed, coffee can taste thin or grassy. If the roasting goes beyond the required levels of Maillard reaction, you may find the cup to be harsh and bitter.
You don’t need to be a coffee roaster to identify and appreciate good Maillard development.
Some signs indicating the influence of the Maillard reaction are rounded sweetness, pleasant cocoa or biscuit-like notes, structured body, and a clean finish.
A great way to train your palate and improve your coffee experience is to compare light, medium, and darker roasts of the same coffee side by side. This will help you understand how acidity, sweetness, and toasted notes change.
Why Roasters Pay Close Attention to the Maillard Phase
This stage is where a lot of crucial decisions are made, especially in the case of specialty coffee.
Roasters pay special attention to the Maillard stage to ensure the coffee is balanced and as intended.
Excessive heat can cause scorching, uneven-development, and accelerate the roast too quickly. On the other hand, if there’s not enough heat, it can make the coffee dull.
Even with the same coffee, two roasters can produce very different cups. One may feel bright and floral, while the other roast could be focused on a heavier body and caramel notes.
Some factors that influence how the reaction progresses are airflow, drum speed, charge temperature, and timing. Even the smallest of changes in these factors can alter the sweetness, body, and clarity.
Not Every Coffee Reacts the Same
The beauty of coffee is in how dynamic it is. Pick any two coffees (from the same region or not), and you’ll see how they behave completely differently.
To give you an example, a coffee bean that has high density absorbs heat more slowly than a low-density coffee bean.
This is because the cellular structure of the bean is much more compact, and so heat doesn’t travel the way it would in a low-density bean. Naturally, the roast progresses differently.
Similarly, processing method, bean size, moisture content, and variety also affect how the Maillard reaction manifests.
That’s why, even though the principle remains the same, the science remains the same, for coffee roasters, every new batch of coffee is an exciting puzzle to be solved.
Now that you know how the Maillard reaction transforms coffee, you can understand why a cup can taste like nuts, brown sugar, and chocolate.
The science behind coffee truly sheds fascinating insights that help us appreciate the bean much more.