Flavour Compound of Last Week - Maltol

Maltol or 3-hydroxy-2-methyl-4H-pyran-4-one is produced primarily during malting and to a limited degree during wort boiling through the Maillard reaction. The Maillard reaction was first described by Louis-Camille Maillard and involves sugars like glucose reacting with amino acids to produce compounds, some of which are flavour-active. The Maillard reaction is very complicated and maltol, rather poetically, is produced through dehydration of a 1-deoxyosone yielded by 2,3-Enolisation of an Amadori product.


Maltol has a freshly baked bread or caramel-like aroma. It is used as a flavouring in food production.

The Maillard reaction is often used interchangeably with the phrase “caramelisation of malt sugars”. Caramelisation is not the same as the Maillard reaction because the Maillard reaction requires the presence of amino acids. Caramelisation is the pyrolysis (splitting by heat) of sugars alone. It is unlikely that caramelisation actually confers much flavour to beer as the temperatures and concentrations of sugar in worts are probably too low to yield a great enough concentration to be perceptible. That is unless you have a very useless kettle which burns wort. Any caramel flavours are likely to be courtesy of Monsieur Maillard and his lovely reaction.

Please note the spelling Maillard. I have known a few people who tried to demonstrate their brilliance by quoting the Maillard reaction who have proved the complete opposite by calling it the Mallard reaction. I assume that this is what happens when you sear duck breast in a hot pan.