Blanching in Cooking and Food Preservation

This simple process maintains foods' flavor, color, and texture

Blanching tomatoes
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Whether cooking certain recipes or preparing to preserve produce, blanching is often a recommended technique. That's because certain fruits and vegetables, such as cauliflower, green beans, and tomatoes, benefit from this simple process that quickly cooks the food and then abruptly stops the cooking. To blanch, food is briefly immersed in boiling water (often just a minute or two), followed by an ice bath to rapidly cool off the food. Blanching is used both by home cooks and in industrial food processing.

Why Blanch?

When a food is blanched properly, the flavor, color, texture, and nutritional value is preserved. Blanching gently softens the outside of the food while keeping the interior crisp, sweetens the produce a little, and causes the vegetable to hold its color for a longer period of time.

  • Vegetables will be crisp-tender and bright in color in salads and on a crudités platter.
  • Before incorporating into a quick-cooking recipe such as a stir-fry, blanching will soften vegetables that take longer to cook like broccoli and carrots.
  • Some of the bitterness is removed from cabbage, leafy greens, and onions after blanching.
  • Blanching loosens the skin on fruits such as tomatoes and peaches to assist in peeling, which is required for certain recipes.
  • Before freezing, drying, and canning, blanching is often called for so the produce is a pleasant texture and color when used later on.

How to Blanch

There are three ways to blanch fruits and vegetables: boiling, steaming, and microwaving. Each is simple to do and requires basic cooking equipment and water. Prepare the produce (wash, peel, slice, chop, etc.) per the recipe or personal preference.

Water or Boiling Method

  1. Set a large pot of salted water to boil.
  2. Once it is boiling, immerse the vegetable or fruit in the boiling water.
  3. Once the water returns to a boil, begin timing for the length of blanching recommended, which is usually just a couple of minutes.
  4. Quickly remove the food items from the boiling water and plunge them into an ice-water bath.
  5. As soon as they're cool, drain the fruit or vegetable and set aside either to use in a recipe or to process for canning, drying, or freezing.

Steaming Method

  1. Add an inch or two of water to a pot that will fit a steamer basket.
  2. Set a steamer basket inside a pot so that the basket is about 3 inches above the bottom of the pan.
  3. Bring the water to a boil and add the vegetables or fruits to the basket in a single layer.
  4. Cover the pot and continue to cook over high heat for as long as recommended. The time begins when the pot is covered. (Steaming will take about 1 1/2 times longer than boiling.)
  5. Transfer to an ice bath immediately.
  6. As soon as they're cool, drain the fruit or vegetable and set aside to use in a recipe or to process for canning, drying, or freezing.

Microwave Method

  1. Place vegetables or fruit in a single layer in a microwave-safe dish.
  2. Add 1/4 to 1/2 cup water to the dish.
  3. Cover and microwave on high for half of the recommended time, uncover and stir, and finish cooking.
  4. Stir again and immediately transfer to an ice bath.
  5. As soon as they're cool, drain the fruit or vegetable and set aside to use in a recipe or to process for canning, drying, or freezing.

Tips

  • Although it may be tempting to skip putting together the ice bath, shocking the food is one of the most important steps. Abruptly ceasing cooking is what assures ideal texture and color.
  • Most recipes will call for adding salt to the blanching water. It not only contributes flavor to the vegetables but also results in less of the foods' sugars and salts leaching into the water. However, the amount of salt can be debatable; some chefs instruct to salt the water as you would for pasta, while others believe the water should taste like brine and be heavily salted.
  • After the fruit or vegetable is added to the boiling water, the water should return to a boil within 1 minute; if it takes longer, it means there is too much food in relationship to water or that the pot is too large.
  • To simplify peeling, before blanching fruit, cut a shallow X in the skin at the bottom.

The Cooling Process

Even after food is removed from the heat, it keeps cooking; vegetable fibers continue to soften, pigments change color, and enzymes are inactivated (which lowers the nutritional values). Plunging the food items into an ice-water bath, called "shocking," halts the cooking process and its effects. Ice water works best because it cools quickly—even a few cubes from your ice tray will make a difference—but if all you have is cold tap water, that will work OK. (Make sure to use the coldest water possible.)

Be aware that leaving the food items in the ice bath for too long will turn them soggy, so it is important to remove them as soon as they are cooled down and drain and pat dry the fruits or vegetables completely. Drying the food thoroughly is important so it doesn't turn soft and add moisture to the recipe.

Blanching Times

The amount of time fruits and vegetables should stay in the boiling water will depend on the food, size, whether it is whole or cut, and the quantity. Because vegetables and fruits are delicate, cooking them for too long (which can be as little as a minute) can turn them limp, soggy, and drab in color. Therefore, it is important to follow the time recommendations.

Blanching Times
Vegetable Blanching Time in Minutes
Artichoke Hearts 7
Asparagus 2 to 4 depending on thickness
Beans ( Green, Snap, or Wax) 3
Beans (Lima, Butter, or Pinto) 2 to 4 depending on size
Broccoli (flowerets) 3
Brussels Sprouts 3 to 5 depending on size
Cabbage 1 1/2 for shredded, 3 for wedges
Carrots 2 for diced, 5 for small
Cauliflower (flowerets) 3
Celery 3
Corn on the Cob 7 to 11 depending on size
Eggplant 4
Greens 2 (3 for  collards)
Kohlrabi 1 for cubed, 3 for whole
Mushrooms (steamed) 3 to 5 depending on sliced or whole and size
Okra 3 to 4 depending on size
Onions (blanch until center is warm) 3 to 7 depending on size
Peas (in the pod) 2 to 3
Peas (shelled) 1 1/2 to 2 1/2
Peppers 3 for strips, 5 for halves
Potatoes 3 to 5
Rutabagas 3
Soybeans (green) 5
Squash (chayote) 2
Squash (summer) 3
Turnips or Parsnips (cubes) 2
Fruits for Peeling Blanching Time in Seconds
Apples  30
Peaches 30
Pears 30 to 60
Tomatoes 30
Follow recommended blanching times to assure crisp-tender produce.

Recipes

Vegetables such as green beans are often blanched in order to enhance their natural green color and soften them to a pleasant texture. If blanching vegetables for a stir-fry, don't shock the vegetables in cold water but instead simply drain and add to the wok.

Other Foods That Need Blanching

In addition to fruits and vegetables, there are other foods that benefit from blanching. Certain almond recipes, such as marzipan and almond cookies, call for blanching the nuts to remove their skins (or purchasing already blanched almonds). When preparing homemade bone broth, the bones are blanched beforehand in order to rid them of impurities. Blanching is also an excellent technique for preventing avocados from turning brown.

Blanching can also be done in a fat such as oil. When making french fries, the cut potatoes are often blanched in medium-heat oil and then cooled before frying them a second time at a higher temperature.