Maillard reaction

What is Maillard reaction?

The formation of color in beer from sugars and amino groups was initially studied by Ling and Malting in 1908. The resulting color is typically brown in nature, which is why this reaction is sometimes referred to as the nonenzymatic browning reaction.

However, Maillard reported the coloring reaction between reducing sugars and amino groups in 1912 and recognized its significance in various fields such as plant pathology, geology, and medicine. As a result, this reaction is widely known as the Maillard reaction.

This reaction involves a complex organic process that occurs between reducing sugars and molecules with a free amino group, such as amino acids, peptides, and proteins. The end products of this reaction are nitrogenous heterocyclic molecules with varying substituents on nitrogen that give brown-like colors. Depending on the source of reducing sugars and amino compounds, the products formed display different colors and flavors.

Maillard reaction - general reaction scheme - nonenzymatic browning reaction
Maillard reaction

The Maillard reaction occurs in three stages. First, the amino group nucleophilically adds to the aldehyde group of reducing sugar, resulting in the formation of glycosylamine. Next, the Amadori rearrangement occurs, leading to the irreversible formation of ketosyl compounds and various products via different reaction pathways, such as enolization, aldol condensation, dehydration, fragmentation of amino acid, and polymerization. This reaction results in the browning, fluorescence (by advanced glycation end products, AGEs), and cross-linking of protein. The products of the Maillard reaction are commonly known as Maillard reaction products (MRPs) or melanoidins.

Some MRPs exhibit antimutagenic and antioxidant activity, while others, such as those found in milk powder, are undesirable. The extent of the reaction is influenced by factors such as water activity, pH, reaction duration, and temperature.