Steaming is a moist heat cooking method. Although cooking occurs at a higher temperature than in braising, stewing or poaching, steaming is one of the most gentle cooking methods as food is not agitated by bubbling liquid during the process. From our junior high science classes, we all know that steam is water converted to its vapor state at the boiling point. Since the boiling point of water is 212° F (100° C) at sea level, the highest temperature at which steam can cook food is 212°F/100°C. You can increase this pressure somewhat by placing steam under pressure, but in the home kitchen, expect steaming to occur right at or around the boiling point of water.
As a cooking method, steaming was used as far back as the Paleolithic Period. Evidence has been found that the Aurignacian people of southern France, considered the first “modern” humans in Europe, cooked foods by wrapping them in wet leaves, a steaming method that is still used today (think tamales).
While steaming is not a method that is very prevalent in Western kitchens, many cultures rely heavily on steaming—China, India, and many North African countries come to mind. I started wondering: Why this stark contrast between cultures that cook with steam and those that do not? The most viable notion that I have found to explain this is that steaming requires little energy because it can be done with a relatively small amount of liquid. In countries where both fuel for fires and water are hard to come by, steaming enabled people to cook a lot of food relative to fuel and water, allowing them to make the most of their resources.
Aside from being a “frugal” cooking method, steaming is also a very healthy cooking method. First, since food is cooked by direct contact between steam (conduction) as well as the movement of the hot vapor through the food (convection), no fat is needed to conduct the heat. Often, just a squirt of lemon juice is all you need to add to a steamed dish. This makes steaming a lower-calorie, low fat cooking method. Food stays moist, too, since it is being bathed in water vapor. Also, since water soluble nutrients (namely Vitamins C and B) don’t leach out into vapor, steaming preserves up to 50% more nutrients than other moist heat cooking methods.