---
title: "What is the Maillard Reaction? Ingredients, Mechanisms and Chemical Development"
description: "The coloring and browning of food is a topic highly valued within the community of chemists who study this scientific field, since the pigmentations and the reactions that form them tend to be very complex."
url: https://www.thebeertimes.com/en/what-is-the-maillard-reaction-ingredients-mechanisms-chemical-development/
date: 2024-05-14
modified: 2026-06-25
author: "Carlos Uhart M."
image: https://www.thebeertimes.com/wp-content/uploads/2016/12/Color_en_la_Cerveza.jpg
categories: ["Culture"]
tags: ["Chemistry", "Ciência", "Color", "Maillard Reaction", "Popular", "Química", "Science", "Technology"]
type: post
lang: en
---

# What is the Maillard Reaction? Ingredients, Mechanisms and Chemical Development

By **[Food Crumbles](https://foodcrumbles.com/maillard-reaction-mechanism-hard-core-chemistry/)**

The [coloring and browning of beverages](https://www.thebeertimes.com/el-color-en-la-cerveza-origen-ajuste-y-medicion/) and food is a topic highly valued within the community of chemists who study this scientific field, since the pigmentations and the reactions that form them tend to be very complex.

![Colors in beer](https://www.thebeertimes.com/wp-content/uploads/2016/12/Color_en_la_Cerveza.jpg)*Colors in beer*

Within this landscape, the golden-brown coloring that some foods acquire is undoubtedly one of the most fascinating topics — particularly interesting because of the multiple, completely different chemical pathways that exist to achieve this coloring, all with the same final result: bananas, grains, meat, sugar, etc.

In this article we will focus on one of these mechanisms, specifically the Maillard reaction — the one responsible for both the [coloring of the barley](https://www.thebeertimes.com/los-diversos-esplendores-de-la-malta/) used in [brewing beer](https://www.thebeertimes.com/como-hacer-cerveza-artesanal-paso-a-paso/) and the very dark crust on a seared steak.

The main products of this reaction are cyclic and polycyclic molecules that contribute [aromas and flavors](https://www.thebeertimes.com/en/morten-meilgaard-and-the-development-of-the-beer-flavor-and-aroma-wheel/) to food — though they also include other molecules that may be carcinogenic, such as [acrylamide](https://www.cancer.gov/espanol/cancer/causas-prevencion/riesgo/dieta/hoja-informativa-acrilamida#:~:text=La%20acrilamida%20es%20una%20sustancia,de%20poliacrilamida%20y%20de%20acrilamida.).

Contenido

- [How food acquires its brown coloring](#How_food_acquires_its_brown_coloring)
- [Chemistry of the Maillard reaction](#Chemistry_of_the_Maillard_reaction)
- [Ingredients for the Maillard reaction](#Ingredients_for_the_Maillard_reaction)
  - [1. Amino group](#1_Amino_group)
  - [2. Reducing sugar](#2_Reducing_sugar)
- [Mechanisms of the Maillard reaction](#Mechanisms_of_the_Maillard_reaction)
  - [1. Amadori and Heyns compounds](#1_Amadori_and_Heyns_compounds)
  - [2. Molecular rearrangement](#2_Molecular_rearrangement)
  - [3. Colored melanoidins](#3_Colored_melanoidins)
- [Frequently Asked Questions (FAQ)](#Frequently_Asked_Questions_FAQ)
  - [1. What is the difference between the Maillard reaction and caramelization?](#1_What_is_the_difference_between_the_Maillard_reaction_and_caramelization)
  - [2. How can the Maillard reaction be accelerated or slowed down when cooking?](#2_How_can_the_Maillard_reaction_be_accelerated_or_slowed_down_when_cooking)
  - [3. What is acrylamide and why is it associated with the dangers of the Maillard reaction?](#3_What_is_acrylamide_and_why_is_it_associated_with_the_dangers_of_the_Maillard_reaction)
  - [4. Why doesn’t common table sugar (sucrose) directly generate the Maillard reaction?](#4_Why_doesn8217t_common_table_sugar_sucrose_directly_generate_the_Maillard_reaction)
  - [5. What specific compounds from the Maillard reaction contribute the aroma of toasted bread or beer?](#5_What_specific_compounds_from_the_Maillard_reaction_contribute_the_aroma_of_toasted_bread_or_beer)
- [Recommended](#Recommended)

## How food acquires its brown coloring

There are two main ways in which food acquires a brown color: enzymatic browning and non-enzymatic browning.

Enzymatic browning is what happens with ripe bananas, for example — a reaction that stops in the presence of intense heat.

![Roasted malts](https://www.thebeertimes.com/wp-content/uploads/2021/07/Maltas-tostadas.jpg)*Roasted malt*

Non-enzymatic browning can be further divided into two types: the Maillard reaction and caramelization.

Caramelization requires high temperatures above 150°C (302°F) and only needs sufficient [sugars](https://www.thebeertimes.com/5-adjuntos-de-azucar-que-podrias-incorporar-a-tu-elaboracion-de-cerveza/) to be present.

The Maillard reaction, on the other hand, can take place at room temperature — though it accelerates rapidly as temperature increases — and requires two types of molecules to proceed: proteins and sugars.

| **Reaction** | **Heat** | **Sugar** | **Proteins** | **Temperature** | **Examples** |
| --- | --- | --- | --- | --- | --- |
| Enzymatic | No | No | No | 20–30 °C | Ripe banana, cut apple, avocado. |
| Caramelization | Yes | Yes | No | >150 °C | Burned sugar, caramel, golden onion. |
| Maillard Reaction | Yes | Yes (reducing sugar) | Yes | >90–140 °C | Toast, grilled meat, beer, coffee. |

## Chemistry of the Maillard reaction

The first description of the Maillard reaction mechanisms dates back to the early twentieth century, when the French scientist [Louis Camille Maillard](https://es.wikipedia.org/wiki/Louis-Camille_Maillard) managed to discover the underlying chemical principles — themselves composed of a series of complex, consecutive reactions.

![Louis Camille Maillard (1878-1936)](https://www.thebeertimes.com/wp-content/uploads/2021/07/Louis-Camille-Maillard.jpg)*Louis Camille Maillard (1878-1936)*

It was in 1913 that Maillard presented his doctoral thesis on the reaction between amino acids and carbohydrates, as a result of research he had conducted on urea metabolism and kidney diseases.

It wasn’t until after World War II, however, that Maillard’s studies were applied to the study of food, when researchers began investigating the reactions that occur when food is heated — generating aromas, flavors and colors in a process we commonly call “browning” or “toasting” when frying, roasting or baking.

It all begins with a sugar and a protein/amino acid, which react to form compounds called Amadori or Heyns products — explained by the reaction of a reducing sugar (aldose or ketose) with an NH2 amine group from the protein.

These molecules continue to react to form new compounds that, from a chemical structure perspective, mostly consist of molecules that incorporate a ring during the reaction.

Ultimately, other large complex molecules called [melanoidins](https://es.wikipedia.org/wiki/Melanoidina) are formed, which eventually give food its characteristic brown coloring.

## Ingredients for the Maillard reaction

Let us now examine the three steps of the Maillard reaction mechanism one by one, starting with the molecules that must be present for it to occur.

### 1. Amino group

For the Maillard reaction to take place, a so-called [amino group](https://es.wikipedia.org/wiki/Grupo_amino) must be present — consisting of one nitrogen atom and two hydrogen atoms: NH2.

This amino group is bonded to a larger molecule (amino acids, for example), which means there may be several other atoms in it, represented by the letter R. This amino group is therefore written as R-NH2.

This type of amino group is commonly found in amino acids, proteins and peptides, where amino acids are the basic building blocks of the other two.

In the Maillard reaction, the amino group often comes from proteins — such as those found in the milk used to make butter.

### 2. Reducing sugar

In addition to the amino group, we also need another ingredient called a reducing sugar — a special type of sugar that possesses a specific reactive group.

First of all, sugar is a carbohydrate, and it is commonly monosaccharides and disaccharides that participate in the Maillard reaction.

A reducing sugar specifically is one that can donate electrons, and for this to happen, an atom must have enough free electrons orbiting around it.

An oxygen atom bonded to a carbon atom with two bonds is one such atom, and therefore sugars that incorporate this group belong to the category of reducing sugars.

In chemistry, these specific groups are known as aldehyde (-COOH) and ketone (-CO-).

![Guía Práctica Catar Cerveza Amazon](https://www.thebeertimes.com/wp-content/uploads/2025/05/Catar-cerveza-300x300.jpg)

[Guía práctica para catar cerveza: Cómo apreciar correctamente todas las cervezas del mundo](https://amzn.to/3LddZmQ)

[Comprar en Amazon](https://amzn.to/3LddZmQ)

In practice, all monosaccharides (such as glucose and fructose) are reducing sugars, as is lactose (a disaccharide). However, sucrose (common granulated table sugar) is not.

## Mechanisms of the Maillard reaction

Now that we have a reducing sugar and an amino group, we can begin to examine the Maillard reaction in detail. The first step is the reaction that occurs between the two to form a molecule.

Over the course of a total of 4 reactions, both “ingredients” rearrange themselves into an [Amadori compound](https://es.wikipedia.org/wiki/Transposici%C3%B3n_de_Amadori#:~:text=Formaci%C3%B3n%20de%20un%20producto%20Amadori,el%20nitr%C3%B3geno%2C%20formando%20una%20cetona.) or a [Heyns compound](https://link.springer.com/article/10.1007/s12161-016-0669-1), depending on the type of sugar involved.

If the sugar has an aldehyde group (-COOH), the result will be an Amadori compound. If it has a ketone group (-CO-), a Heyns compound will be formed.

### 1. Amadori and Heyns compounds

The chemical reactions involved in the formation of these compounds involve organic chemistry processes.

This means many structural molecular diagrams and vectors indicating which compounds are formed, how they are added, and how the reactions occur.

![Formation of the Amadori compound](https://www.thebeertimes.com/wp-content/uploads/2021/07/Formacion-del-compuesto-Amadori.gif)*Amadori compound*

In this step, a sugar (in this case glucose) reacts with an amino group (which may be bonded to a protein) to form an Amadori compound — the starting point for the subsequent reactions that will generate toasted aromas, flavors and colorings.

It all begins with the sugar and the amino group forming a molecule. This molecule then loses water before rearranging into an Amadori compound. Reactions with bidirectional arrows indicate the reaction is reversible.

### 2. Molecular rearrangement

Up to this point, the types of reactions have been limited to roughly two: one forming an Amadori compound and another forming a Heyns compound, both occurring in very similar ways.

![Reactions](https://www.thebeertimes.com/wp-content/uploads/2021/07/Reacciones.gif)*Molecular rearrangement*

In the image, the molecule on the far left is the Amadori compound from the previous reaction.

If this molecule is in an acidic environment (H+), the reaction can take place, resulting in the formation of a molecule with two double-bond oxygen atoms.

The two products formed in this reaction can go on to do all sorts of things. One option is that the aminoketone (upper product) can react with another aminoketone to form a ring, resulting in the formation of pyrazines — which are highly aromatic.

![Strecker reaction](https://www.thebeertimes.com/wp-content/uploads/2021/07/Reaccion-de-Strecker.gif)*Strecker reaction*

Once these molecules with two double-bond oxygen atoms have formed, they can participate in the [Strecker reaction or synthesis](https://es.wikipedia.org/wiki/S%C3%ADntesis_de_Strecker) — the point at which low-molecular-weight aromatic molecules are formed that are easily detected by the sense of smell, and the variation in reaction pathways begins to increase dramatically.

At this stage, the initial formation of very faint yellow colors also occurs, along with the production of some slightly unpleasant aromas.

### 3. Colored melanoidins

At this point, many different reactions are taking place simultaneously, with the products of each reacting with their neighbors, driven by the specific conditions present.

![Reddish melanoidin](https://www.thebeertimes.com/wp-content/uploads/2021/07/Melanoidina-color-rojo.gif)*Example of a reddish melanoidin*

This is the point at which the colorings associated with the Maillard reaction begin to form, with molecules reacting to build complex structures containing many rings — producing colored melanoidins ranging from pale yellow to very dark brown and even black.

At this stage, the Maillard reaction is remarkably complex. A simple illustration: the reaction of glucose with ammonia alone results in more than 15 different compounds, while the reaction of glucose with glycine can produce more than 24 different compounds.

The complete mechanism of the Maillard reaction has not yet been fully elucidated, but it is certain that it involves the polymerization of many of the compounds formed in the second phase.

The Maillard reaction is, in short, a large set of somewhat “uncontrolled” chemical reactions that give rise to many different molecules, which then react with each other to form yet more molecules.

It has always been a genuine challenge for scientists to discover precisely what is happening, but understanding this set of chemical reactions has provided enough clues to describe its basic functioning.

Using this knowledge of the Maillard reaction mechanism, we can now begin to reason about how to control this reaction in food, and understand the origin of the [different types of malts](https://www.thebeertimes.com/aprendiendo-a-comprender-las-maltas-base/) used in brewing beer.

## Frequently Asked Questions (FAQ)

### 1. What is the difference between the Maillard reaction and caramelization?

Although both belong to non-enzymatic browning, the main difference lies in the reactants and the temperature. Caramelization is the pyrolysis of sugars (requiring high temperatures, generally above 150°C) and does not involve proteins. The Maillard reaction, on the other hand, is an interaction between a reducing sugar and an amino group (proteins), and can occur at much lower temperatures (from around 90°C, or even at room temperature during prolonged storage).

### 2. How can the Maillard reaction be accelerated or slowed down when cooking?

The speed of this reaction depends on pH, moisture and temperature. To accelerate it (for example, to brown meat or vegetables faster), you can raise the pH by adding a pinch of baking soda or reduce the moisture on the surface. Conversely, to slow it down, add acidic ingredients (such as lemon juice or vinegar), lower the temperature, or increase the water content during cooking.

### 3. What is acrylamide and why is it associated with the dangers of the Maillard reaction?

Acrylamide is an organic chemical compound classified as a probable human carcinogen. It forms naturally during the Maillard reaction at high temperatures (generally above 120°C), especially when the amino acid asparagine (very common in potatoes and grains) reacts with reducing sugars. This is why excessively frying or toasting foods such as french fries, bread or coffee increases the concentration of this substance.

### 4. Why doesn’t common table sugar (sucrose) directly generate the Maillard reaction?

Sucrose is a non-reducing disaccharide because its chemical bonds block the functional groups (aldehyde or ketone) needed to donate electrons and initiate the process. For sucrose to participate in the Maillard reaction, it must first be hydrolyzed (broken down) into its basic components — glucose and fructose (which are reducing sugars) — through the action of heat, time, or an acidic medium.

### 5. What specific compounds from the Maillard reaction contribute the aroma of toasted bread or beer?

The main compounds responsible for the complex, highly volatile aromas are pyrazines and pyrroles — cyclic compounds synthesized from Strecker degradation in the intermediate phases of the reaction. Depending on the specific amino acids in the food, these chemical compounds generate aromatic descriptors that the human sense of smell identifies as notes of toast, nuts, biscuit, coffee or bread crust.

## Recommended

- [Blockchain in the brewing industry: Transforming sustainability and efficiency](https://www.thebeertimes.com/blockchain-en-la-industria-cervecera-transformando-la-sostenibilidad-y-eficiencia/)
- [The 10 most influential people in Chilean craft beer over the last decade](https://www.thebeertimes.com/en/title-the-10-most-influential-people-in-chilean-craft-beer-over-the-last-decade/)