You’ve seen it a million times in recipes: One egg, at room temperature. Two sticks of butter, at room temperature. You know how to count eggs and butter sticks, but exactly what temperature is “room temperature”?
Maddeningly for fastidious cooks, “room temperature” is a subjective term in recipes, because my kitchen’s temperature is not necessarily the same as yours. Essentially, “room temperature” is a shorthand for “not refrigerator temperature,” which is a relatively recent phenomenon. After all, the icebox wasn’t invented until the 19th century; prior to that, most foods were kept at either ambient or cellar temperatures, but not the chilly mid-30 degrees we find in fridges. By the 1950s, however, refrigerators had become commonplace in American kitchens and previously unrefrigerated ingredients, such as butter and eggs, became staples of the chiller. Consequently, cookbooks began referring to “room temperature” more and more in order to differentiate from refrigerator temperature.
What temperature is “room temperature”?
“Room temperature” isn’t a specific temperature at all, nor even a universally agreed-upon temperature range. Ambient indoor temperatures vary wildly from place to place around the globe, but that’s not quite the same as room temperature, which is the comfortable temperature range we usually maintain in our homes.
Back in the late 1960s, a Danish scientist named Povl Ole Fanger started researching the concept of thermal comfort in an attempt to determine the optimal indoor temperature for the human body, based on metabolic rate, clothing, air speed, humidity, and other factors. His findings significantly influenced HVAC design and operation, and have remained the foundation for international standards and guidelines for indoor air temperature. If you’ve ever wondered why your office is perpetually kept at a crisp 70 degrees Fahrenheit, you have Fanger to thank.
Thermal comfort is not universal everywhere, and it even varies among people of different sexes and ages within the same geographic designation. Generally speaking, however, indoor temperatures in the Western world are often set somewhere in the range of 68 to 74 degrees Fahrenheit, depending on the season; in sub-Saharan Africa, however, many people prefer a temperature closer to 79 degrees Fahrenheit.
All of this is to say that my room temperature is not necessarily the same as your room temperature, which can present a problem when it comes to precise cooking. Cookbooks would be better off specifying the temperature ingredients should be at, rather than using a relative term—but for the purposes of this article, when I refer to “room temperature” I mean the Western definition of the low 70s.
Why does “room temperature” matter for cooking?
Generally speaking, allowing fridge-cold ingredients to warm up before cooking them does a couple of things. First, it equalizes their temperature with other ingredients that aren’t typically refrigerated, so they all can cook at the same rate. Second, it helps hot pans stay hot, because a pile of cold ingredients in a heated pan will simply steam instead of sizzle. Third, it may help individual ingredients to cook more evenly, especially thick cuts of meat that would otherwise turn well-done on the outside while staying close to raw in the center. (J. Kenji López-Alt has called BS on this theory, however, so take it with a grain of salt.)
Even more critically, temperature influences the structure of emulsions such as vinaigrettes and mayonnaise, which are unstable by their very nature. (This is why commercially produced mayo and vinaigrettes usually contain a stabilizer such as lecithin.) As a science class reminder, an emulsion is a mixture of two incompatible liquids, such as oil and water, where one is dispersed as droplets throughout the other. At room temperature, the ingredients in the emulsion are more fluid and less viscous. This makes it easier to blend the two components together, facilitating a more thorough and even mixing process. Cold liquids, on the other hand, can be thicker and more resistant to blending, making it harder to achieve a stable emulsion. Likewise, warm liquids often make emulsions more susceptible to breaking, as the dispersed droplets start to coalesce and separate.
This applies to baking as well. Many cake batters, such as this pound cake recipe, start out as emulsions: You cream together butter and sugar (the “fat” component) before slowly adding in the eggs and milk or cream (the “water” component). Adding the latter too quickly, or at a temperature that’s significantly different from that of the butter, will cause the batter to break and become gritty. It will still make cake, but the texture will be flat and gummy rather than airy and light. Getting all of your ingredients to around 70 degrees Fahrenheit before mixing will allow the butter to achieve a fluffier consistency and emulsify with the liquid components more easily.
How does room temperature affect yeasted bread doughs?
Bread bakers often say that temperature is an ingredient. If you’re making sourdough, the temperature of your kitchen will affect the flavor and growth rate of your starter. A warm kitchen will speed up fermentation and produce sharper sour notes, while a cold kitchen keeps fermentation humming along at a more moderate pace.
Beyond that, however, bakers also refer to a concept known as Desired Dough Temperature (DDT), which refers to the ideal temperature of yeasted dough during mixing and kneading. Think of DDT as the "sweet spot" for your dough's temperature, which is usually between 75 to 78 degrees Fahrenheit. If the dough is too cold, it will ferment slowly, taking a long time to rise and develop flavor. On the other hand, if the dough is too warm, it will ferment too quickly, leading to undesirable results like an overly airy or uneven texture.
Room temperature plays a role in determining the initial temperature of the dough before any mixing or kneading occurs. If the room is warm, it can warm up the ingredients, making the dough warmer from the start. If the room is cold, the dough will start off cooler. To achieve the desired dough temperature, bakers often need to adjust the temperature of their ingredients. They might use warmer or colder water to mix the dough, depending on the room temperature and the desired outcome. By controlling the dough temperature, bakers can better manage the fermentation process.
You can calculate DDT the long way, which will help you get a better understanding of how the temperature of your room and other ingredients will impact your final dough, or you can use an online DDT calculator as a shortcut.
How can I quickly warm up ingredients to room temperature?
Let’s say you want to cook a recipe that requires “room temperature” ingredients but don’t have the time or patience to wait for those ingredients to come up to temperature. All is not lost.
For liquids like milk, water, or eggs, add them to a bowl or container and place that inside another larger bowl filled with warm tap water. The warm water will transfer its heat to the ingredient, helping it reach room temperature faster. (Make sure the water is not too hot, because you can end up inadvertently cooking your eggs.) Placing the container on a heating pad set to low would also work. You won’t necessarily enter the “danger zone” (i.e. the temperature range in which spoilage bacteria most readily grows) with these quick methods; the USDA recommends that you avoid leaving eggs out of the fridge for any longer than two hours.
For solid ingredients like butter or cream cheese, use a microwave to gently warm them up. Cut blocks into smaller pieces, place them on a microwave-safe plate, and microwave in short bursts (5 to 10 seconds) until softened to room temperature, being careful not to melt them.
In all of these cases, it’s important to have a well-calibrated and trustworthy thermometer. Being aware of the temperature of your kitchen and your ingredients will help you to understand how they react when they’re cooked, regardless of whatever “room temperature” means where you live.
