How now, brown cow?

Amino acids. Sugars. Flavors. And the Maillard reaction, explained simply.

Steak - Maillard reaction

1-Minute NomNom

Why does beef turn brown on the outside when you cook it? Or for that matter, why do pork, chicken and other meats turn brown too? It is the doings of the Maillard reaction, which is also behind the browning of dough that gives us the golden brown crusts found on breads and donuts.Bread - brown crust - maillard reaction

Simply put

Maillard reactions start with the amino acids (which are the building blocks of proteins) found in many foods. When heated, they react with sugars — such as glucose — found in the food to form new flavor compounds. These flavor compounds continue to react with more amino acids to form much larger molecules that give us the brown crusts we see on meats, breads and donuts.Spare ribs - Maillard reaction

Because there are different types of amino acids and sugars found in different foods, the flavor compounds that form are also different. In other words, the same Maillard reaction gives us the different flavors we associate with specific foods: a beef steak definitely does not taste the same as pork ribs or a donut!

That’s the simple explanation.

Now the science…

Here is the science behind it, also explained simply.

The sugars that react with the amino acids in Maillard reactions must be a particular type of sugar known as reducing sugars. These are sugars with an aldehyde group (or are capable of forming an aldehyde group). An aldehyde group has (see diagram below):

Aldehyde1) a carbon atom doubled bonded to an oxygen atom

2) the carbon atom is also bonded to an hydrogen atom.

This aldehyde group is bonded to a much larger chemical group of hydrocarbons (made up of only carbon and hydrogen atoms), commonly denoted as “R”.

When the amino acids react with the reducing sugars, the first set of flavor compounds that are formed are known as dicarbonyls. Which is just a fancy name for saying that there are two carbonyl groups.

carbonylAnd what is a carbonyl group? It is (see diagram to the right):

1) a carbon atom doubled bonded to an oxygen atom

2) the carbon atom is also bonded to two other groups of compounds (denoted as “A” and “B” in the diagram).

(the smart cookies among you would have noticed that that makes an aldehyde a carbonyl!)

donuts - maillard reaction

When these flavor compounds react with more amino acids, they form polymers (a molecule made of smaller molecules) called melanoidins, giving us the brown crusts of meats, breads and donuts.

The Maillard reaction was first described over 100 years ago, but to this day, the chemistry is still not fully understood. What we do understand is how yummy it makes our food!

 

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photos: in order – depositphotos/keko64; .shock; brebcachirapbogdan

 

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