Maillard Reaction

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Maillard Reaction Definition and Mechanism
That Maillard reaction is a set of reactions between proteins and sugars that browns food and other products.

The Maillard reaction is a set of chemical reactions between amino acids and reducing sugars that browns food. Named after the French chemist Louis-Camille Maillard, who first described it in the early 20th century, this non-enzymatic browning reaction is responsible for the flavors, aromas, and colors in a wide range of cooked foods, from seared steaks to roasted coffee.

What Is the Maillard Reaction?

The Maillard reaction is a chemical reaction between amino acids (proteins) and reducing sugars that occurs when food is cooked, particularly at high temperatures. Unlike caramelization, which only involves sugars, the Maillard reaction requires both amino acids and reducing sugars to generate a complex array of molecules that contribute to the characteristic flavors and colors of cooked foods.

History and Naming

The reaction was first described by Louis-Camille Maillard in 1912. John E. Hodge later provided a mechanism for the reaction in the 1950s, delineating the intricate pathways that amino acids and sugars take to create numerous complex compounds.

Importance in Cooking Chemistry

The Maillard reaction plays an essential role in developing complex flavors, colors, and aromas. It occurs in a myriad of foods, from meat to bread, vegetables, and even dairy products. The unique profiles of many beloved dishes and food items are attributed to the Maillard reaction. Poorly managing the reaction results in a burnt flavor and the formation of undesirable compounds.

Examples of Foods Browned by the Maillard Reaction

Many foods get their characteristic color in flavor due (at least in part) to the Maillard reaction. Here are examples, along with some molecules produced by the reaction:

  • Steak – Melanoidins
  • Bread crust – Furfurals and other compounds
  • Roasted coffee – Various aromatic compounds
  • French fries – Hydroxymethylfurfural (HMF)
  • Pancakes – Melanoidins
  • Cookies
  • Roasted almonds – Pyrazines
  • Barbecued meat
  • Toasted marshmallows – Hydroxymethylfurfural (HMF)
  • Roast chicken – Various aromatic compounds
  • Fried onions – Thiazoles
  • Roasted peanuts – Pyrazines
  • Grilled fish – Furans
  • Bagels
  • Caramelized milk – Furan-2-carbaldehyde
  • Toasted coconut – Acetaldehyde
  • Pretzels – Melanoidins
  • Popcorn – Pyridines
  • Grilled vegetables – Thiophenes
  • Roasted garlic – Diallyl disulfide
  • Malt whiskey
  • Beer
  • Toffee
  • Dulce de leche
  • Dried and condensed milk
  • Tortillas
  • Dried fruit
  • Pandan (an herb)

Examples of How Cooks Use the Maillard Reaction

  • Cooks: Chefs often sear meat at high temperatures to initiate the Maillard reaction, developing complex flavors and a pleasing aroma.
  • Coffee Roasters: The roasting process leverages the Maillard reaction to create the aromatic compounds that define coffee’s character.
  • Bakers: Achieving a golden-brown crust in bread and pastries relies on the Maillard reaction.
  • Confectionery: Caramelized milk in certain candies owes its flavor to Maillard reactions (as well as to caramelization).

Maillard Reaction Mechanism

The Maillard reaction occurs in multiple stages:

  1. Initial Stage: Amino acids react with reducing sugars to form a Schiff base.
  2. Intermediate Stage: The Schiff base undergoes Amadori rearrangement to produce various intermediate compounds.
  3. Final Stage: These compounds further break down into various volatile and non-volatile compounds, such as pyrazines, furans, and melanoidins, which contribute to flavor and color.

Key Factors Affecting the Outcome

There is a reason why most baking recipes call for a 350 °F oven and why searing a steak improves its colors and flavor. You need a high enough temperature to promote the Maillard reaction, yet not so much heat that you get undesirable, possibly toxic products.

  • Temperature: Higher temperatures accelerate the reaction.
  • pH: The reaction is more prevalent in alkaline conditions. This why applying lye (a strong base) to pretzels aids in darkening them.
  • Water Activity: A low moisture environment aids the Maillard reaction. For this reason, be sure you pat meat dry before searing it.

Other Types of Browning

The Maillard reaction is but one of the processes that results in food browning.

  • Enzymatic browning: This type of browning occurs in fruits like apples and bananas when exposed to air. It often occurs in concert with the Maillard reaction, as in coffee and dried fruit.
  • Oxidative browning: Oxidative browning occurs in certain meats and seafood. When you cook meat, it browns due to both oxidation and the Maillard reaction.
  • Caramelization: This process involves the pyrolysis of sugar.

Maillard Reaction vs. Caramelization

Both the Maillard reaction and caramelization are types of non-enzymatic browning, but caramelization involves only sugars and occurs at higher temperatures. It lacks the complexity and range of flavors and aromas attributed to the Maillard reaction, which needs both amino acids and sugars.

The Maillard Reaction and Acrylamide

Excessive Maillard reactions lead to burnt flavors and undesirable darkening. Acrylamide, a potential carcinogen, can also form. Control of time and temperature helps manage the extent of the Maillard reaction.

Several strategies can minimize the formation of acrylamide:

  1. Reducing Cooking Time and Temperature: Lowering the temperature and cooking time minimizes acrylamide formation.
  2. Altering pH: Adjusting the pH of food reduces acrylamide formation. More acidic conditions inhibit its formation.
  3. Use of Asparaginase: This enzyme breaks down asparagine, one of the precursors to acrylamide, before cooking.
  4. Choice of Ingredients: Certain types of sugars and amino acids are more prone to forming acrylamide, so ingredient choice also plays a role.

Fun Maillard Reaction Facts

The Maillard reaction doesn’t just apply to foods that people eat.

  • The reaction occurs when bodies become preserved in peat bogs. The acidic bog environment browns the skin and changes hair color to ginger/red tones.
  • The Maillard reaction is one of the reactions that preserves paleofeces.
  • The heat produced while making silage promotes the Maillard reaction, reducing the protein and calories available in the animal feed.

References

  • Harrison, T. J.; v, G. R. (2005). “An expeditious, high-yielding construction of the food aroma compounds 6-acetyl-1,2,3,4-tetrahydropyridine and 2-acetyl-1-pyrroline”. J. Org. Chem. 70 (26): 10872–74. doi:10.1021/jo051940a
  • McGee, Harold (2004). On Food and Cooking: The Science and Lore of the Kitchen. New York: Scribner. ISBN 978-0-684-80001-1.
  • Nursten, Harry (2007). “The Chemistry of Nonenzymic Browning”. The Maillard Reaction. ISBN 978-0-85404-964-6. doi:10.1039/9781847552570-00005
  • Tamanna, N.; Mahmood, N. (2015). “Food Processing and Maillard Reaction Products: Effect on Human Health and Nutrition”. International Journal of Food Science. 2015: 526762. doi:10.1155/2015/526762
  • Tareke, E.; Rydberg, P.; Karlsson, Patrik; Eriksson, Sune; Törnqvist, Margareta (2002). “Analysis of acrylamide, a carcinogen formed in heated foodstuffs”. J. Agric. Food Chem. 50 (17): 4998–5006. doi:10.1021/jf020302f