The basis of good flavour

Why is toasted bread so delicious? Why does grilled meat taste so much more aromatic than meat boiled in water? And where does coffee get its intense flavour from? Alongside the delicious basic ingredient, it is theoretically pure chemistry. French biochemist Louis Camille Maillard discovered this and the complex processes involved over 100 years ago, and called it the Maillard reaction. In doing so, he highlighted a phenomenon that represents the basis of practically every type of food since the discovery of fire.

How flavour is created

At first glance, the optical and flavour-related changes to foods in a frying pan appear to just be a reaction to heat. But for foods which contain protein, such as meat, potatoes and fried eggs, there are various processes in play which basically have nothing to do with burning. Instead, condensation, dehydration, isomerization and cyclization – the Maillard reaction – are responsible for the crusts on all foods which are roasted, baked and fried.

Carbohydrates react with amino acids when exposed to heat. Aromatic substances are formed in the process, and these are similar to a sugary, tangy glaze – not to be confused with caramelization, although this can occur at the same time.

We perceive the brown end products – called melanoidins – of the Maillard reaction as having an intense flavour. Incidentally, for meat we know when the reaction has finished because it no longer sticks to the bottom of the stainless steel pan or the grill – i.e. it can be moved again. Then it's time to turn it over.

Which foods undergo the Maillard reaction?

Meat is most commonly mentioned when it comes to the Maillard reaction. In addition, it is also the main reason in terms of flavour as to why we sear meat – and not because the meat needs to be sealed. The reaction also occurs in bread when the crust forms, as well as later when it is toasted. This is particularly noticeable in lye products. In the alkaline environment (aqueous solutions with a high pH value, as in the case of lye), the sugar and protein components in the dough are much more reactive. More colour and aroma is produced with the same baking duration than for untreated products.

Coffee also benefits from these chemical processes. Only the Maillard reaction, which is triggered when the beans are roasted, produces the main sweet and malty flavour – the only reason the coffee bean can be enjoyed at all. It is also essential in beer brewing, as it determines the aroma and colour of the beer. However, the Maillard reaction also takes places at lower temperatures. In the case of champagne, for example, an interaction with residual sugar can occur during storage, which makes the refined sparkling wine taste a little like fresh bread.

Info

There are several ways to encourage the Maillard reaction when searing meat – i.e. to produce a more potent crust and a more intense roasted flavour: a short while before cooking, you can scatter some salt over the meat to draw moisture out of it and therefore accelerate the reaction. You can add proteins, by placing the meat in milk or egg, for example. Or you can simply increase the heat, turn the stove up, or stoke the fire. «But make sure the meat doesn't develop any black spots or begin to char.»

Good crust, bad crust?

Shortly after the turn of the century, many studies showed that acrylamide develops in certain foodstuffs during the Maillard reaction. This is a substance that is considered to be “probably carcinogenic to humans”, as stated by the International Agency for Research on Cancer. The highest levels of acrylamide are found in harshly heated potato products such as roesti potatoes, crisps and chips, as well as cereal products such as crispbread, crackers and biscuits. However, either no or only a negligible amount of acrylamide is created in meat and fish – regardless of the cooking method.

To reduce the development of acrylamide it is therefore important to ensure that potato products are not allowed to turn too brown. The Swiss Federal Food Safety and Veterinary Office also recommends observing the following basic principle when baking at home: go for gold.