One of the main chemical processes responsible for the unique flavor of Maple Syrup is the Maillard reaction. In this article, I describe what the Maillard reaction is, how it affects the flavor of Maple Syrup, and how you can best utilize this principle in your Maple-Syrup-making!

Who was “Maillard?”

The Maillard reaction is named after a French physician and chemist name Louis Camille Maillard (1878-1936) who published a paper in 1912 that described the chemical reaction between amino acids and sugars at high temperatures. Prior to his work on amino acids, he made important contributions to the study of kidney disorders.

Is making maple syrup a chemical change?

Yes. The process of heating maple sap removes much of the water through boiling, but there are also chemical changes that take place. The Maillard reaction is one of these chemical processes and is one of the key factors in giving maple syrup its unique flavor (Reference: The Science of Maple Syrup).

Filtered maple syrup
Crystal Clear Maple Syrup!

What is the Maillard Reaction in Simple Terms?

The Maillard reaction, or Maillard browning, is the chemical reaction between amino acids and simple sugars at elevated temperatures.

The Maillard reaction is commonly known for some well-known examples such as the browning of the crust of baked bread, searing of steak, toasted marshmallows, pretzel skins, the golden-brown color of French fries, and the amber color of maple syrup.

Interestingly, Maillard browning is also responsible for browning of the skin used in some self-tanning lotions!

What molecules are involved in the Maillard reactions?

The Maillard reaction involves simple sugars and proteins. The sugars can be glucose and fructose. The proteins are typically peptides and amino acids (Source: NIH – A Perspective on the Maillard Reaction).

What Flavors does the Maillard Reaction Produce?

Some of the flavors associated with the Maillard reaction have been described as tasting like bread crust, popcorn, even flowers.

Is the Maillard Reaction the Same as Caramelization?

The Maillard reaction is not the same as caramelization. While the two are similar, and often occur simultaneously, they are not the same process. Caramelization is the liquifying of sugar using heat. No amino acids are necessary for caramelization to occur.

Why Causes the Different Colors of Maple Syrup?

There are three types of simple sugars in Maple syrup, glucose, fructose, and sucrose, however the sap’s sugar composition changes over the course of the maple-tapping season.

Early on in the season, the sap consists of a larger portion of sucrose, but as the season progresses, and the outdoor temperatures increase, microbial processes in the tree change the relative concentrations of the sugars by breaking the sucrose down into fructose and glucose at a faster rate.

The extent to which the Maillard reaction will occur can be predicted based upon the relative concentrations of the sap’s sugar content.

The Maillard reaction only involves glucose and fructose, but not sucrose. For this reason, sap collected earlier in the season that is higher in sucrose, tends to be lighter in color, as there is less of the Maillard browning occuring due to the reduced presence of glucose and fructose as compared to later in the season.

The more glucose and fructose sugars in the boiling sap and the longer the sap boils, the darker the syrup will be (ref).

The Maple Syrup Institute has a color grading system used for classifying the colors of Maple syrup, in which the light transmission of the syrup is measured and rated.

  • Golden color/delicate taste syrup has a light transmittance of not less than 75%
  • Amber between 74.9 and 50%
  • Dark between 49.9 and 25%
  • Very Dark, less than 25% light transmittance

What Other Factors Affect the Color of Maple Syrup?

In addition to Maillard browning occurring more or less, depending on the proportions of fructose, glucose, and sucrose, there are other factors that affect the color of Maple syrup.

The color of finished Maple syrup can also be affected by the pH of the Maple sap, the duration over which the sap is boiled, and the rate at which the temperature is applied for heating.

In general, Maple syrup from sap harvested earlier in the season is lighter and syrup from sap harvested later in the season is darker.

Maple Syrup Making
Maple Syrup Bottles – light to dark based on time of the season of sap harvesting

Is Maillard reaction carcinogenic?

Under certain circumstances, the Maillard reaction has been known to create a carcinogen called Acrylamide in small amounts (ref), which can be harmful to humans and their pets.

Fortunately, the constituent parts necessary to produce Acrylamide are not present in the boiling of Maple syrup, nor are the temperatures high enough to produce any known carcinogens (Hamlet et al., 2016), which require a temperature of 120 C (248 deg F) or above to form.

What are the benefits of the Maillard reaction?

During heat treatment such as frying, roasting, boiling and baking, the Maillard reaction improves food in taste, flavor, and color.


The Maillard reaction is one of the main processes responsible for the delicious taste of Maple syrup. The later in the season that your maple sap is harvested, the more Maillard browning occurs when the sap is boiled, producing a darker, richer tasting Maple syrup.

Interested in learning more about the Maillard reaction? Listen to the podcast episode on this subject:

What is the Maillard Reaction and how can I use it to Make Better Maple Syrup?

As always, thanks for reading, and I hope this article was helpful!

Additional Articles in this Series on Maple Syrup Making!

These are the links to the other articles in this series:

Check out the “How to Make Maple Syrup Podcast!”

Or listen right from your browser:

The “How to Make Maple Syrup Podcast!” is enjoyed by hundreds of listeners each week during the maple-sugaring season. We’d love for you to join us! We discuss our favorite tips and tricks for making maple syrup as well as interesting information related to the golden elixir!

See the Steps for Making Maple Syrup on YouTube!

How to Make Maple Syrup on YouTube - Practical Mechanic
Watch “How to Make Maple Syrup in 4 Minutes” on YouTube!