What is Blanching?
Blanching can mean a few different things depending on who’s using the word and what application you’re talking about. In the most basic use of the term, blanching refers to very briefly par cooking an item for later use, usually using boiling water or hot fat as a cooking medium.
Why Would You Need to Blanch Something?
- To preserve the quality of the food and make it easier to store usually by freezing. Blanching the food helps to preserve it by destroying bacteria that causes food to spoil and enzymes that discolor food, as seen when raw potatoes turn brown shortly after being sliced.
- It helps to save time in the kitchen, especially restaurant kitchens. Restaurant customers don’t care how long it takes something to cook, all they know is that they’re hungry NOW! Large batches of food such as vegetables will be par cooked and then later finished to order.
- Blanching helps remove undesirable flavors. Some vegetables and meats with strong flavors, (such as veal tripe and brussel sprouts), are sometimes blanched to make their flavor a little more mild.
- Sometimes you have to blanch something in order to prep it for further use. For example, you need to blanch tomatoes to loosen their skins before you can make tomato concassé and you need to blanch veal sweet breads to loosen the membrane before peeling.
Basic Blanching Technique
Knowing how to blanch vegetables properly is a must have technique in any cooks arsenal. Here is the basic method that you should use.
Blanching Green Vegetables
- Bring salted water to a rolling boil in a large pot.
- Place green vegetable in boiling water until tender. Whether or not you prefer your blanched vegetables cooked all the way through, or al dente (meaning firm to the bite), is a personal preference. First, learn how to successfully blanch your vegetables all the way through, and then if you prefer them al dente, just back off on the blanching time a little bit.
- Once the vegetable becomes tender and the green color is solidified, shock in ice water. This causes the vegetable to cool rapidly, keeping it from overcooking which could turn it mushy and affect your beautiful green color.
Blanching Root Vegetables
The technique for blanching root vegetables with complex starches such as carrots and potatoes is a little different from blanching green vegetables such as spinach, broccoli and green beans. Because root vegetables are more dense, placing them directly into boiling water can cause them to cook unevenly.
To properly blanch root vegetables, start them in a pot with cold salted water and bring to a simmer. Cook them until desired tenderness is reached and then stop the cooking by shocking them in an ice bath.
Deep Water Blanching
In his book “The French Laundry Cookbook,” Chef Thomas Keller talks about the important of “deep water blanching. ” The term deep water blanching refers to blanching your vegetables in a large enough pot so that when you add your vegetable, that water maintains a rolling boil or comes back to a boil very quickly. This is based on the basic fact that the longer you cook your vegetables, the more chance you have of your color fading before they reach the proper texture.
The Importance of Adding Salt
Salt is a very important component to blanching vegetables but there is a lot of folklore surrounding the actual reason why salt is added.
A lot of people have the common misconception that adding salt to your blanching water will raise the temperature of the water, allowing you to cook your vegetables faster. Although this is technically true, it isn’t exactly accurate. Let me explain.
Two of my favorite books that I have come across in my studies are “What Einstein Told His Cook” and “What Einstein Told His Cook 2” by Robert L. Wolke. According to Wolke, adding one tablespoon of salt (or 20 grams to be exact), to 5 quarts of water, will cause the water’s boiling point to rise by only seven hundredths of one degree Fahrenheit.
However, there is an extremely valid reason for adding salt to your blanching water. Again, citing Wolke, in his book “What Einstein Told His Cook 2,” he talks about the molecular make up of chlorophyll molecules, the chemical that keeps vegetables green. Not to get too technical or geeky on you, but this is an important concept to understand.
A chlorophyll molecule consists of carbon, hydrogen, oxygen and nitrogen atoms with a magnesium atom in the middle. Basically what happens, is when you go to blanch your vegetables, if they are slightly acidic, which most commonly are, an acid’s hydrogen atom will replace the magnesium atom, turning your vegetable to a drab, green-gray color.
Now where the debate gets interesting is that some chefs will try and cancel out the acidity by adding baking soda (which is sodium bicarbonate) to the blanching water, making it more alkaline. The problem with this however is that the sodium bicarbonate breaks down the complex carbohydrates contained in the vegetable, making the vegetable mushy, not to mention giving off a soapy taste.
Now that we got that geek speak out of the way, here’s the punch line. Adding salt to your blanching water basically accomplishes the same thing by making it harder for the hydrogen atoms to break through the cell membrane and replace the magnesium atom. So long story short, adding salt to your blanching water improves flavor and helps keep greens from going gray.