“Without Maillard chemistry we would not have a dark bread crust or golden brown turkey,” wrote the authors of a Royal Society of Chemistry book about the reaction, “our cakes and pastries would be pale and anemic, and we would lose the distinctive color of French onion soup.” The Maillard Reaction—which actually entails a series of reactions—isn’t all toasty goodness, however. It’s also responsible for making apples turn brown, which many people find unappetizing “despite negligible effect on flavor,” the authors write.

Louis Camille Maillard, the chemist for whom the reaction is named, didn’t set out to do culinary research when he first described the browning effect in 1912. But his name is still evoked frequently among chefs, nutritionists, scientists, and others interested in how proteins and sugars together unlock tasty new molecules in a variety of foods right around 350 degrees. (There’s some debate about the exact temperature; some put it closer to 335 degrees.)

Maillard aside, 350 is simply a moderate temperature—another reason it works well for many recipes. It’s hot enough to cook things fairly quickly but no so hot that your dish burns.

But many chefs aren’t fixated on any one temperature, and instead think of their craft in terms of ranges: “Really low, under 275 degrees; moderate, between 275 and 350; high, over 350 but under, say 425; and maximum,” the cookbook author Mark Bittman once told Slate. It wasn’t until the 20th century that recipes routinely included precise temperatures—even in the 1950s, it was common to see terms like “slow oven” and “moderate oven” in place of any number. The very concept of cooking at a constant and precise temperature is technologically driven, an extension of a device that seemed miraculous at the time it was introduced: The regulator.

“The regulator makes scientific cooking possible to the most unscientific woman, and few realize how many perfect recipes are spoiled by wrong handling of the oven heat,” The New York Tribune wrote in a 1919 piece about the the Clark Jewel Gas Range. “[E]ven if the housewife does not know that a slow oven is about 250 to 300 degrees, a moderate oven 350, a hot oven 400 to 450, and very hot 450 to 475, the little wheel of the regulator tells her these facts in words as well as in figures and she can translate any recipe that calls for a moderate or slow or hot oven accordingly.”

The device was located on the oven, and usually involved a wheel or pointer you could turn to the temperature of your choice. This was connected to a thermometer-and-valve contraption that would expand as the oven got hotter, and prevent the temperature from going up when the upper limit was reached. Today, the ability to set a constant temperature seems so inherent to the concept of how an oven works—it’s just what ovens do. But when regulators were new, they were a marvel of automation.