Understanding how the Maillard reaction works is important for any coffee enthusiast, roaster, retailer, or home brewer.
Why? Because the Maillard reaction is responsible for many of the flavors we enjoy in coffee - including the roasted, nutty, and chocolatey flavors.
In this article we'll explore the Maillard reaction - what it is, how it works, and how it impacts coffee.
The History
The Maillard reaction is named after French chemist Louis-Camille Maillard, who first described it in 1912.
It was discovered when Maillard was studying the reactions that occur when amino acids and sugars are heated together.
At the time, it was known that these two substances could react to create new flavors, but the mechanism behind this reaction was not yet understood.
Maillard's research helped to shed light on how the reaction works, and how it can be used to create new and wonderful flavors.
How the Reaction Works
The Maillard reaction is responsible for the browning of food when it's cooked. For example, the bread you toast in the morning gets its color and flavor from the Maillard reaction.
The same is true for the steak you grill, the chicken you roast, and even the beer you drink.
At its core, the Maillard reaction is a chemical reaction between amino acids and reducing sugars that gives food a brown color and distinct flavor.
Amino acids are the building blocks of proteins. They are present in coffee beans in the form of proteins.
Reducing sugars are carbohydrates that can be broken down to form other molecules, such as alcohols.
When these two molecules react, they create hundreds of new molecules that contribute to flavor and color.
Amino Acids
During the reaction, the amino acids undergo a series of changes.
First, the amino acids lose water molecules. This process is called dehydration.
As the water is lost, the amino acids start to bond with each other.
These new bonds are called cross-links. The cross-links make the amino acids harder to break down, which is why cooked meat is tougher than raw meat.
The cross-links also give the food a chewy texture.
Reducing Sugars and Carbohydrates
The reducing sugars also change during the reaction.
They break down into smaller molecules, such as aldehydes and ketones.
These molecules contribute to the flavor of the food.
Aldehydes are responsible for the fruity flavors in coffee, while ketones contribute to the nutty and chocolatey flavors.
Citric Acids
Citric acids are a type of acid that is found in citrus fruits. They are responsible for the sour taste in citrus fruits, and they can also contribute to the flavor of coffee.
Although not directly involved in the Maillard reaction, they can interact with the molecules that are created during the reaction, acting as catalysts to speed up the reaction.
Citric acids speed up the reaction by breaking down the bonds between the amino acids and the sugars. This makes it easier for the amino acids and sugars to react with each other.
The Process
We think of the reaction as a "process". This is because it actually happens in multiple steps.
Once the temperature of the coffee beans reaches around 300°F (148°C), the Maillard reaction starts to occur.
The heat from the roaster causes the water molecules to be lost from the amino acids, and the cross-linking begins. Amadori compounds are also formed at this stage.
The second step of the reaction starts around 400°F (204°C).
At this temperature, the reducing sugars start to break down into smaller molecules. These molecules then react with the amino acids to create new flavors and colors.
The Maillard reaction is a complex process that results in the formation of hundreds of new molecules.
In Coffee
In coffee, the Maillard reaction occurs during the roasting process.
As the beans are heated, their amino acids and sugars react to create new molecules that contribute to flavor and color.
The Maillard reaction is responsible for the rich, roasted flavors that we enjoy in coffee.
It also contributes to the color of the coffee bean, and affects the way that coffee tastes when brewed.
Impact on Color
The Maillard reaction is changes the color of coffee beans during roasting.
As the beans roast, their amino acids and sugars react to create new molecules that contribute to color.
The longer the beans are roasted, the more color they will develop.
This is why dark roast coffees are typically darker in color than light roast coffees.
Impact on Flavor
The Maillard reaction is responsible for many of the flavors we enjoy in coffee, including the roasted, nutty, and chocolatey flavors.
It also contributes to the body and mouthfeel of coffee. The longer the beans are roasted, the more flavor they will develop.
This is why dark roast coffees typically have more intense flavors than light roast coffees.
Impact on Aroma
The Maillard reaction also contributes to the aroma of coffee.
As the beans roast, their amino acids and sugars react to create new molecules that contribute to aroma.
The longer the beans are roasted, the more aroma they will develop.
This is why dark roast coffees typically have more intense aromas than light roast coffees.
The Maillard reaction is a key part of the roasting process, and it's responsible for the flavors, colors, and aromas we enjoy in coffee.
The Science
When viewed in terms of chemical compounds, the maillard reaction can be said to consist of three main types of reaction.
First, there is the formation of N-glycosylamines from the sugar and amino acid components. This compound is key in further reactions, as it can lead to the formation of other maillard reaction products.
Second, there are the so-called "rearrangement reactions", in which the structure of the N-glycosylamines is altered. This can lead to the formation of compounds such as pyrazines and furans, which are important in providing flavor to coffee.
Finally, there are the "degradation reactions", in which the N-glycosylamines are broken down into simpler products. These products can contribute to both the flavor and the color of coffee.
Molecules - Volatile and Non-Volatile
The coffee molecules that are formed during the maillard reaction can be divided into two groups: volatile and non-volatile.
The volatile molecules are responsible for the aroma of coffee, while the non-volatile molecules contribute to both flavor and color.
Acrylamide
One of the maillard reaction products that has attracted attention in recent years is acrylamide.
Acrylamide is a compound that is formed during the maillard reaction, and it has been shown to be carcinogenic in animal studies.
However, it should be noted that the levels of acrylamide found in coffee are generally low, and there is no evidence that coffee consumption is harmful to human health.
In fact, coffee is a rich source of antioxidants, which are believed to protect against some types of cancer.
Summary
The maillard reaction is a complex process that occurs when sugars and amino acids react together. The reaction results in the formation of hundreds of new molecules that contribute to the flavor and color of coffee.
The maillard reaction is responsible for the roasted, nutty, and chocolatey flavors that we enjoy in coffee, as well as the dark color of roasted beans.
Finally, it also contributes to the aroma of coffee, and the longer the beans are roasted, the more intense the flavors, colors, and aromas will be.
FAQ
What is the maillard reaction?
The maillard reaction is a complex process that occurs when sugars and amino acids react together. The reaction results in the formation of hundreds of new molecules that contribute to the flavor and color of coffee.
What are the benefits of the maillard reaction?
The maillard reaction is responsible for the roasted, nutty, and chocolatey flavors that we enjoy in coffee, as well as the dark color of roasted beans. The maillard reaction also contributes to the aroma of coffee, and the longer the beans are roasted, the more intense the flavors, colors, and aromas will be.
What are the products of the maillard reaction?
The maillard reaction results in the formation of hundreds of new molecules that contribute to the flavor and color of coffee. These molecules can be divided into two groups: volatile and non-volatile. The volatile molecules are responsible for the aroma of coffee, while the non-volatile molecules contribute to both flavor and color.
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