Boiling, simmering, poaching — what is the difference?

When you read a recipe, you will often see instructions to bring something to a boil, cook at a simmer, poach in a liquid or so forth. Have you ever thought what those terms mean or if they really make a difference? When my husband (who is a good cook) insists that any bubbles means it is boiling, I tell him that the amount and vigorousness of the bubbling makes a difference. Even though he is often right (don’t tell him I said that), this is one time he is not totally correct.

As you heat water in a pan on the stove, you will first see bubbles at the bottom of the pan. These bubbles rise slightly in the pan but then collapse. As the water gets hot not only on the bottom but throughout, these bubbles rise all the way to the surface before it collapses. This is the point at which your water is considered boiling. If you live at or near sea-level, this will be at 212°F. As I mentioned in a prior tip, that number drops by 2° for every 1000 feet above sea level. For example, at 5000 ft water will boil at approximately 202°F. Once it reaches true boiling, the temperature of the water will not increase despite what you do with the heat level of your burner. So, to decrease the chances of boiling over the pot, decrease your heat source to keep the liquid at a gentle boil. As long as it remains at a boil, the temperature of the water will be the same.

What foods do you cook in boiling water? Pasta, some grains and even vegetables. Cooking vegetables quickly in boiling water helps to retain their flavor and color. This is called blanching and is often followed by a dunk in ice water to prevent over-cooking. Boiling is great for reducing the volume of a liquid such as when you want to concentrate it. Boiling should not be used for more delicate foods which might be harmed by the agitation of the boiling water.

The term “simmering” is sometimes called a “gentle boil” although some experts will argue with that term and say it is not a boil at all. It may be defined as “just below a boil”. You may see bubbles on the sides and bottom of the pan but they should disappear if the liquid is stirred with only an occasional bubble breaking the surface. The water temperature is usually around 180°–200°. It is used to cook foods more slowly and gently. It is also what you aim for when making soup or stock. Simmering over a period of time creates a depth of flavor in those dishes that you will not get in quicker cooking.

Poaching is a technique of cooking a food item in a liquid. The liquid should be just barely simmering and the temperature should be around 160°-180° depending on what food you are poaching. If you are poaching fish or chicken, you want to aim nearer 160° as the meat will get tough and dry at higher temperatures. If you are poaching an egg, you will need water about 180°.

Depending on the dish you are cooking, a visual inspection of your water may be all you need. However, it is definitely worth investigating in a good instant-read thermometer. There are many good ones out there but I love the Thermapen from Thermoworks.

Who would have thought there was so much to learn about boiling water? The next time someone tells you they can’t even boil water, think of all you can teach them!