Meaning of Boiling, Parboiling, Blanching, Simmering, Steaming in cooking.
Boiling means bringing water to 100 degrees Celsius (212 degrees Fahrenheit) in a high-sided pot or tea kettle. Let the water come to a full rolling boil (when the bubbles are rapidly breaking the surface). Covering the pot speeds the process by trapping surface heat.
Parboiling and Blanching means pre-cooking tough or salty foods to soften their textures and sometimes to remove harsh flavors or soften tough skin. Rice is sometimes parboiled (or converted) and then packaged to shorten cooking time and retain nutrients. Tomatoes can be blanched to loosen their skins.
Certain dense vegetables, such as carrots, potatoes, and turnips, may be parboiled (cooked briefly in boiling water) to soften them slightly before another method finishes cooking them. This technique guarantees that all the ingredients in the dish finish cooking at the same time.
Blanching, or plunging vegetables or fruits into boiling water for a few seconds and then into cold water to stop the cooking process, helps cooks remove the skins from tomatoes and peaches. Some vegetables, like green beans, are blanched before they are frozen or canned to help retain their color and flavor.
Simmering means bringing liquid to a gentle pre-boil. In a simmer, tiny bubbles break the surface gently. Simmering occurs at a lower temperature, just below a boil, or 180 degrees Fahrenheit, and is used for long and slow cooking.
Steaming is the gentlest way to cook. Steaming is better than boiling or poaching for retaining a food’s color, flavor, texture, shape, and nutrients. Steaming often involves placing food over simmering water on a perforated rack in a covered pot.
You can steam in two ways: in a perforated steamer set over simmering water (and covered) or in a deep, covered pot or saucepan holding about 1 to 2 inches. of water. The latter method works especially well for vegetables like broccoli.
When you steam foods set in a pan of water in the oven, it is called a water bath.
Boil or Steam?
All sorts of vegetables benefit from boiling and steaming. When it comes to choosing between the two techniques, steaming is more gentle and better retains the texture and color of vegetables. Boiling is a more aggressive process and tends to break down the texture of vegetables, which is desirable if you are making purees or mashed potatoes.