Maillard reaction

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Go easy on the toast

We are quick to blame the food industry for all that is wrong with the food supply. Plastic residues in baby food, process contaminants in soy sauce, too much fat in the burgers, too much salt in the soup. I could go on and on and rightly so but did you know that there are some easy steps you can take as well to reduce contaminant formation? Today’s blog will focus on the simple toast. Even the most challenged cook can prepare toasted bread, but do we all know what dangers can lurk in there?

Be the master of the toaster (Photo: Donovan Govan)

Be the master of the toaster (Photo: Donovan Govan)

To state the obvious, toast is bread that has been browned by exposure to radiant heat. This browning is the result of Maillard reactions that alter the flavour of the bread. Bread has been toasted for centuries, initially to make stale bread more palatable. Open flame toasting or oven toasting have now been mostly replaced by the custom made toaster with a more precise control of the degree of toasting. And it is here you come in because you can steer the degree of browning by controlling time and temperature and thus the amount of Maillard reaction products that are formed.

The browning reaction

Just a few words about the Maillard reaction so you get the importance of the events happening during heating. It is actually vitally important in the preparation or presentation of many types of food and is named after chemist Louis-Camille Maillard, who first described it in 1912. It is a form of nonenzymatic browning involving a chemical reaction between amino acids and reducing sugars in the food, usually but not exclusively requiring heat. In the process, a complex mixture of hundreds of different flavour compounds are created. These compounds, in turn, break down to form yet more new flavour compounds, and so on. Most of these new molecules are produced in incredibly minute quantities, but that doesn’t mean they’re unimportant. Each type of food has a very distinctive set of flavour compounds that are formed during the Maillard reaction.

There are two factors, dryness and temperature, that are the key controls for the rate of the Maillard reaction. High-temperature heating speeds up the Maillard reaction because heat both increases the rate of chemical reactions and accelerates the evaporation of water. As the food dries, the concentration of reactant compounds increases and the temperature climbs more rapidly.

Acrylamide formed during toasting

Unfortunately, acrylamide is one Maillard reaction product formed at high temperatures. Production of acrylamide during heating is temperature-dependent and increases as food is heated for longer periods of time.  Its discovery in some cooked starchy foods in 2002 prompted concerns about the carcinogenicity of those foods. In laboratory studies, acrylamide had been shown to cause cancer in animals, but at levels much higher than those seen in foods. Experiments are still underway to determine whether the much lower levels of acrylamide seen in food pose a health risk to people.

Toast bread to light brown and avoid burning it (Photo: DaGoaty)

Toast bread to light brown and avoid burning it (Photo: DaGoaty)

In the meantime it may pay off to be cautious. Certain foods are more likely to contain acrylamide than others. These include potato products (especially French fries and potato chips), coffee, and foods made from grains (such as breakfast cereal, cookies, and toast). These foods are often part of a regular diet. But if you want to lower acrylamide intake, reducing your intake of these foods is one way to do so.

Toasting bread to a light brown color, rather than a dark brown color, lowers the amount of acrylamide. Very brown or black areas contain the most acrylamide. So go easy on the toaster to be on the safe side.

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