I was going to write two separate posts about boiling and steaming but lumping them together seems to make more sense. Boiling then transitioning to steaming. It might sound too much like grade school but, in cooking, it pays to know exactly what it means to boil water.
Let’s start with what boiling means. It means heating the water to reach boiling point. In more nerdy terms, it means heating the water to create pressure equal to the surrounding air. At its most basic, it means bringing up the temperature of water to 212F. Simple? Not really. Altitude affects the boiling point of water. Water boils at 212F at sea level but, at a higher altitude, the boiling point is lower because the air pressure is lower.
How do we know if water is boiling? One technique is to watch for steam above the water. Another, if you want to be really precise, is to use a thermometer. I prefer the bubble technique. Like this.
Left photo: As water heats up, small bubbles form at the bottom of the pot. This is sometimes called the poaching temperature. The water is hot but there is no perceptible agitation. This is the ideal temperature for poaching eggs.
Right photo: As the temperature rises, the bubbles will move upward. This means that the water is starting to simmer and the bubble movement will start causing agitation on the surface.
Left photo: When the small bubbles start to rise continuously, the slight agitation on the surface becomes constant. The water is simmering at this point.
Right photo: As the water nears its boiling point, the rising bubbles will get larger and there will be more agitation on the surface.
When the surface is covered with large bubbles, the water starts to steam profusely. This is the boiling point.
Now, let’s watch those bubbles from the surface.
On the left, the small bubbles are rising.
On the right, agitation on the surface is starting at the top of the photo. The water is almost simmering.
Left photo: The water has passed the simmering stage and is starting to boil. Note the size of the bubbles.
Right photo: And the water reaches boiling point.
So what’s the big deal about boiling water? Depending on what you’re cooking, to have to know when to put it in the hot water. Spaghetti, for instance, must be dropped into water that is boiling profusely. If the water is not hot enough, the uncooked pasta will expel too much starch in the water. The pasta needs all that starch to stay firm. If the starch goes into the water instead, you get thickened cloudy water and soggy pasta.
Then, there’s the matter of bacteria. Before there was bottled water, mothers boiled and cooled the water for their children’s milk. Bacteria can’t survive at boiling point but unless the water actually reached boiling point, then the heating process becomes totally useless.
One obvious question is whether it is okay to turn down the heat once the water has reached its boiling point. That depends on what you’re cooking. If you’re going to simmer meat, then, turn down the heat by all means. But if you boiled water because you intend to steam the food, that’s another matter.
When steaming food, the food cooks in the heat of the steam. The food does not touch the water but is subjected to the moist and hot environment of the steam that the boiling water creates. I always thought that was pretty obvious until someone asked in the puto recipe post if the water should already be boiling before putting the food in the steamer. So, a few things about steaming.
Steaming is kind of similar to baking. In baking, the reason for preheating the oven is to make sure that when the food goes in, it starts cooking immediately. Otherwise, a cake, for instance, won’t rise properly. In steaming, the steam has to be there already to provide the heat when the food goes in because the actual cooking won’t really start until there is sufficient heat.
Think of it as shocking the food with extreme heat as though insisting to the food to go and start cooking. And this is especially true when steaming bread like puto — you have to shock the batter with extreme heat at once to make it start rising instantly. Otherwise, you get dense and soggy puto.
I can’t explain it in chemical terms (yes, cooking is a lot of chemistry) but I can say from experience that the texture of food that was placed in the steamer before there was steam is different from food that has been steamed correctly (i.e., placed in the steamer when the water underneath was already boiling and giving off steam).
Now, the next question of the same person. What should be the setting of the stove once the steamer is in place? Another reader who was trying to be helpful told the first reader to keep the stove at medium setting. Is that correct?
The thing about steaming is that there has to be a constant supply of steam in which the food can cook. If the heat is lowered and the water drops to simmering, there won’t be enough steam to cook the food. The cooking will take longer and the texture of the food will be affected. In short, the stove should be set to keep the water boiling so that it is giving off steam continuously.
What the setting should be depends on the kind of cooking vessel and steamer you’re using. In my case, I place the stack of steamer baskets in a wok, Chinese style. That means the water is not covered and it needs a constant high temperature to keep it boiling. Try keeping the water boiling in an uncovered pot and see if the setting of the stove would be the same if the pot were covered.
Like I said at the beginning of this post, boiling is about creating pressure in the water. And the pressure is simply greater if the heat is contained as when a pot is covered. So, my wok being uncovered, I keep the heat on high. If your steaming equipment is such that there is no extraneous loss of heat, then, you can probably lower the heat to medium.