Why is 350 degrees Fahrenheit the magical oven temperature for delicious food?
Why are baked goods brown? Why are roasted veggies more fragrant and flavorful than raw veggies? Why does browning meat before adding them to soups and chilis enhance the flavor?
If you binge on food science or cooking shows on Netflix and Youtube like me, you’ve probably stumbled across the term “Maillard reaction.” You can credit this reaction to the works of French chemist, Louis Camille Maillard.
Like caramelization, the Maillard reaction is a series of nonenzymatic browning reactions. It is called nonenzymatic because the reaction uses heat energy. For contrast, enzymatic browning is a reaction that relies on an enzyme. An apple exposed to air turning brown is an example of enzymatic browning. So how are caramelization and the Maillard reaction different? While caramelization only involves the heating of sugar (like the sugar crust on a crème brûlée), the Maillard reaction is a series of reactions between sugars and proteins. Thus, it commonly occurs in protein-rich foods like meats and baked goods with milk.
I know I sound super geeky, but put it this way: without this chemical process, we would live a bland dietary existence lacking the flavorful complexity created by roasting, baking, or frying foods. Take coffee beans, for example. A mug of coffee will not taste like coffee unless the beans have been roasted to draw out the nutty and deep flavors.
Now let’s break the Maillard reaction down.
At high temperatures, amino acids (the fundamental building blocks of proteins) and sugars react to form new compounds. These new compounds react with themselves over and over to ultimately synthesize hundreds of different compounds that contribute to flavor and smell. This is why baked goods recipes often call for oven temperature of 350 degrees Fahrenheit, an optimal temperature for the reaction to occur.
In the kitchen, there are four main ways to optimize the browning process for maximum flavor and efficiency in foods:
1. Remove moisture
2. Increase pressure
3. Raise the pH
4. Add more proteins and sugars
Remove Excess Moisture
A favorite dinner vegetable is pan fried zucchini. A trick I use is to lay zucchini slices on a plate, generously sprinkle salt on them, and wait 5 minutes. The salt draws out the moisture from the zucchini slices so that I can easily blot the water off. Why do I do this?
The less moisture a food has, the faster the Maillard reaction occurs. Water has a high heat capacity, meaning that it can absorb a lot of heat energy without a large increase in temperature. If the zucchini has a lot of water, the water diverts heat energy away from the food, and the temperature won’t climb above water’s relatively low boiling point. Enough water would have to evaporate before the zucchini increases in temperature and the Maillard reaction begins. Who has time for that? That said, cooks try to perfect the balance between the Maillard reaction and the moisture of the food. We want a chicken to undergo the Maillard reaction to evolve rich flavors, yet no one wants to eat a dry chicken no matter how flavorful it is!
Increase Pressure
Another way to expedite the cooking process is to use a pressure cooker. Not only do pressure cookers speed up the cooking process, they help the food retain much of its moisture. This sounds contradictory to what you just read. To clarify, it is not moisture itself that slows the Maillard reaction, but rather water's low boiling point at sea level pressure. In high pressure environments, water's boiling point rises, thus making moisture less of an issue. The hotter steam and moisture will help heat the food and achieve optimal Maillard reaction temperatures faster.
Raise pH
Browning is also influenced by pH. Maillard reaction rate increases as the pH increases (i.e. less acidic/more alkaline).
The pH scale is measured from 1-14 and is based on hydrogen ion (H+) concentrations. Distilled water has a neutral pH of 7. Acids like lemon juice and vinegar have a pH less than 7. Bases like baking soda and lye have a pH greater than 7.
Adding acids, which have a lot of hydrogen ions, to food can protonate amino acids. Protonation is the addition of a hydrogen ion to the amino acid, which changes its chemical structure in such a way that the amino acid can no longer participate in the Maillard reaction. In short, adding acids can kill some components of the Maillard reaction.
On the other hand, adding a base (a higher pH) will increase the rate of the Maillard reaction. Chinese marinades often incorporate egg whites or baking soda before stir frying.
Fun fact: Pretzels are brushed in a mixture of lye (high pH) and water to ensure an even dark, brown crust.
Add More Proteins and Sugars
Lastly, adding more of the two main reactants of the Maillard reaction (amino acids and sugars) will increase the rate at which it occurs. That is why meats are marinated with sweet teriyaki sauce or buttermilk. These added proteins and sugars will result in the production of different and novel flavors.
To conclude, the Maillard reaction makes food worth eating. Just to show how delicious the Maillard reaction is, once the cavemen invented cooking, the human race never looked back!
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