Em que temperatura ocorre a reação de Maillard?

The Maillard reaction can occur at a wide range of temperatures, but the lower limit is not well-defined. It can even occur at room temperature, providing some flavoring components (for example) to ripening cheeses and Seranno ham. At high temperatures (over 300°F/150°C), it will noticeably occur on many foods in a matter of minutes, so you can actually watch things "brown." At lower temperatures, it may take hours, days, or even years for the effects to be noticeable. Water inhibits the faster reactions, but at lower temperatures it actually can help the reaction by allowing proteins and sugars more freedom to circulate.

In Harold McGee's Em Alimentação e da Cozinha (revised ed.), he states (p. 779):

There are exceptions to the rule that browning reactions require temperatures above the boil. Alkaline conditions, concentrated solutions of carbohydrates and amino acids, and prolonged cooking times can all generate Maillard colors and aromas in moist foods. For example, alkaline egg whites, rich in protein, with a trace of glucose, but 90% water, will become tan-colored when simmered for 12 hours. The base liquid for brewing beer, a water extract of barley malt that contains reactive sugars and amino acids from the germinated grains, deepens in color and flavor with several hours of boiling. Watery meat or chicken stock will do the same as it's boiled down to make a concentrated demiglace. Persimmon pudding turns nearly black thanks to its combination of reactive glucose, alkaline baking soda, and hours of cooking; balsamic vinegar turns nearly black over the course of years!

Note that while alkaline conditions help, they are clearly not necessary (e.g., balsamic vinegar). Another standard example for non-alkaline conditions is traditional pumpernickel bread, which is steam baked for 12-24 hours usually at oven temperatures ranging around 225-250°F (110-120°C). The interior of the bread does not get much above normal boiling temperature, but a significant color change can clearly be seen in such a humid, relatively low-temperature environment.

Interestingly, despite the information in many cooking sources, many of the earliest studies of Maillard reactions were in systems varying from room temperature to slightly above body temperature, from the browning reactions that create the color of soil to internal reactions in the human body that are now thought to contribute significantly to the aging process and some diseases. Maillard reactions also play a role in the natural changes in moist food observed to happen at room temperature when stored over years, like when you discover a jar or can of food in the back of the pantry and find that the food has turned brownish.

At very high or very low temperatures, Maillard reactions are often secondary to other processes such as caramelização e escurecimento enzimático.

To summarize, here's a helpful poster that shows effects at various temperatures. Briefly:

• Above 400°F (200°C) - mostly caramelization, with the possibility of burning with prolonged heating
• ~330°-400°F (165-200°C) - increasing caramelization with higher temps, which uses up sugars and thus inhibits Maillard at the high end of this range
• ~300-330°F (150-165°C) - Maillard progresses at a fast pace, causing browning noticeably within minutes
• ~212-300°F (100-150°C) - Maillard gets slower as temperature goes lower, generally requiring many hours near the boiling point of water
• ~130-212°F (55-100°C) - Maillard requires water, high protein, sugar, and alkaline conditions to advance noticeably in a matter of hours; generally can take days
• Below 130°F (55°C) - Enzymatic browning is often more significant in many foods than Maillard, but Maillard will still occur over periods from days or months to years, with progressively longer times at lower temperatures

(In some cases, certain reactions can be activated by a short time at a high temperature, which then can lead to faster browning below boiling or even near room temperature.)

One final, but very important, note: the Maillard reaction is a very general process that occurs between all sorts of amino acids and sugars. It thus also can produce a lot of different flavor components and products, in addition to the browning. Different reactions between particular amino acids and sugars will also occur at different rates depending on temperature.

This, I think, may be part of the reason for the confusion among various professional cooking sources about the "minimum" temperatures. Many of the reactions that produce the classic "Maillard taste" and "Maillard smell" components don't really begin to happen appreciably until about 250°F (120°C), and they won't happen fast until 300°F (150°C) or so. Maillard reactions at lower temperatures produce different taste and smell components, which often could be characterized as more "earthy." While browning still happens at a slower pace, the results will actually taste different. But because reaction products will always depend on the exact amino acids and sugars involved, as well as other conditions (moisture, pH), it's difficult to divide temperature ranges into clear flavor zones.

Caramelization is the oxidation of sugar, a process used extensively in cooking for the resulting nutty flavor and brown color. Caramelization is a type of non-enzymatic browning reaction. As the process occurs, volatile chemicals are released producing the characteristic caramel flavor. The reaction involves the removal of water (as steam) and the break down of the sugar. The caramelization reaction depends on the type of sugar. Sucrose and glucose caramelize around 160C (320F) and fructose caramelizes at 110C (230F).

Caramelization temperatures Sugar Temperature

Fructose 110° C, 230° F

Galactose 160° C, 320° F

Glucose 160° C, 320° F

Maltose 180° C, 356° F

Sucrose 160° C, 320° F

The highest rate of the color development is caused by fructose as caramelization of fructose starts at 110C. Baked goods made from honey or fructose syrup will therefore give a darker color. Source:

http://www.scienceofcooking.com/caramelization.htm

Since muscle tissue naturally contains glucose (galactose and fructose consumed buy the body are converted to glucose by the liver), muscle tissue (steak) caramelizes at a minimum of 160° C, 320° F. if you would like to test this, take an induction cooktop and set it to 300° F, when the pan has come to temp, place your meat in. it will cook without getting any of the nice crust you like (also it will take forever to cook, about 40 minutes for a 1" boneless steak to mid rare 130°F).

Since I'm working in the field of biochemistry with amino sugars like occuring in mushrooms or seafood, I know that the maillard reaction occurs at room temperature, in water and even in absence of amino acids, since these sugars are able to react with itself.

Greetz

Goodness, What a detailed explanation of simple, settled, and well understood science. Forget food. There is a huge natural world out there which has been explored scientifically. The Millard reaction, although notable as an interesting observation in cuisine, has it roots in chemistry as what is known as oxidation. This is the natural, but sometimes slow decomposition of energetic compounds such as sugars, proteins, etc. oxidation occurs at all temperatures, just as evaporation of water occurs at all ambient temperatures. Just as water cannot be liquid over 100C, some molecules are extremely unstable over other temps. What we think of as Cooking temperatures are not good measures of accurate, scientific representations of temperature because they typically measure the temperature of a specific section of work product what we are interested in (such as the center of a steak). Millard reaction is, as unscientificly defined, as a mild burning, isn't really quantifiable in the sense you are looking for. Proteins, cabrohydrates, and fats oxidize at all temperaturs, but faster at rates above boiling. See: smoking points of fats. Sorry.