Review – The Maillard Reaction

Having just introduced the first member of the non-enzymatic browning reaction duo, caramelisation, the stage is set to make the acquaintance of the second, the Maillard reaction (pronounced my-YARD for us English speakers). If you are squinting your eyes and rubbing your forehead, thinking “caramelisation?”, then now would be a good time to pour another coffee and put this post front and centre on your screen. Conversely, spare yourself my poor writing and watch this video with the infinitely more charismatic Dr. Kiki.

Good? Let’s move on!

It has been over 100 years since the scientist Louis-Camille Maillard began to seriously study the high temperature reaction of amino acids and sugars, and in so doing he laid the first stone in the foundation of food science. His 1912 paper described the typical colour and aroma changes but was short on detailed chemical explanations. These would not come until some 40 years later, when advances in chemistry allowed John Hodge to fill in the missing pieces and propose some intricate mechanisms that would explain how the chemicals physically rearrange to give new, enticingly flavoured and strongly coloured compounds. Despite their great contributions, some of these are actually very small and are the most recognisable to our noses and palates. They have strange names like 2-acetyl-1-pyrroline, responsible for the familiar smell of freshly baked bread. Others are enormous chemicals that have names so long I would need a full page to list even one. They are all included under the much shorter name, melanoidins, and are the substances that give the rich brown colour that makes our salivary glands weep tears of joy.

That isn’t to say that every product of the Maillard reaction is met with such a rapturous welcome. Acrylamide is a possible carcinogen, and a study by Swedish scientists showed that highly processed food contained appreciable levels of the chemical. Fortunately, science has taken the gauntlet and companies have come up with incredibly innovative solutions that lower the level of acrylamide in foods without destroying the taste. There are a few other baddies such as methylglyoxal and hydroxymethyl furfural that also have toxic properties, but by and large I think we can take comfort in the fact that humans have been cooking food for many thousands of years and we can still live to a ripe age of one hundred and something years. Probably not the time to forego the wonders of fire and start eating everything raw again. Because then we would be exposing ourselves to dangerous, pathogenic microorganisms! Right? Yes, right.

The Maillard reaction is a magnificent process that millennia of foodies have cherished. There are even suggestions that melanoidins may have beneficial properties that go beyond tastiness. One recent study hinted they could serve as food for helpful bacteria in the intestines while helping fight off infections from harmful bacteria, or that certain melanoidins could be useful as antioxidants or food preservatives. To give some indication of just how importantly this process is viewed, it even has its own society dedicated to the “growing recognition of the role reactive carbonyl compounds play in food technology, nutrition and tissue aging in biology and medicine.” Yippee! Where can I sign up? Sounds like some absolutely killer masquerades and cotillions.

In the future we will certainly have much more information about the part played in human health by the many products of the Maillard reaction.  For now we can just forget the biochemistry and surrender ourselves to the sweet, smoky, nutty taste of a well grilled steak, as our heavy browed ancestors did so often in the past.

If you are interested in lovely graphics then jump on over to this amazing site and check out a one page primer on the Maillard reaction.

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