Question

write a 2-3 page document describing the Maillard reaction (the browning reaction).

Answer 1

Answer

MAILLARD REACTION

The French physicist and chemist Louis Camille Maillard (1878–1936) discovered a chemical reaction occurs between amino acids and reducing sugars which generate different flavours and brown colour when foods are processed or cooked at high temperature. This reaction named as Maillard reaction. It is also called as non-enzymatic browning reaction. Therefore, it is often used in food industry to change taste, colour, and aroma of food items.

The steps involved in this reaction is given below,

STEP 1 high temperature Sugar -CHO + NH, amino acids – Schiff Base Amadori Product (Colourless Product)

STEP 2 Dehydration and fragmentation Amadori Product (Colourless Product) Hydroxymethylfurfural (HMF) fission products such as pyruvaldehyde and diacetyl are formed.

STEP 3 Aldol condensation Hydroxymethylfurfural (HMF). pyruvaldehyde & diacetyl Melanoidins This product is responsible for different aroma and brown colour

An example of Maillard reaction is given below,

C6H1206 + __NH₂ + HCHO HO Sugar part amino acid Pyridine or Pyrazine NH NH2 X=CH, Y=H or X=N, Y=CH3 Formation of 2-amino-3-methylimidazo[4,5-fbquinoline and 2-amino-3,8- dimethylimidazo[4,5-f]quinoxaline

The condensation of an amino acid with an aldose to form a Schiff base was first recognized by Maillard. Hodge (1953) first described the advanced glycation end-products (AGEs), formation involved in Maillard reaction products (MRPs). The products' formation can be divided into three major steps depending on colour formation. In the first step, amino acids and sugar condense, and following condensation, Amadori rearrangement and 1-amino-1deoxy2 ketose form. In the second step, sugar molecules undergo dehydration and fragmentation. Hydroxymethylfurfural (HMF) fission products such as pyruvaldehyde and diacetyl are formed in this intermediate stage. The products formed in this step are slightly yellow or colourless. In the third final step, aldol condensation occurs and finally the heterocyclic nitrogenous compounds form, melanoidins, which is brown coloured with different aroma. The final stage of this reaction formed unsaturated, brown nitrogeneous polymers and co-polymers.

The research work aimed at understanding the early stage of the Maillard reaction in heated and stored food-related protein/sugar systems. This work has been carried out using milk or milk proteins. Also, the Maillard reaction is of special importance in milk. However, milk is the only naturally occurring protein food and also have a high content of reducing sugars. A range of plant and animal proteins to the Maillard reaction showed that the percentage of lysine destroyed increased with its percentage content in the protein.