Here I am discussing boiling as a cooking technique. There are a variety of aspects of boiling that can change the nutrients, and even taste of the food being cooked. Let us explore together what boiling is all about.
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Boiling Food
Wikipedia: Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point, the temperature at which the vapour pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmosphere.
Water Temperature
Boiling, simmering and poaching are similar methods of wet liquid-cooking that differs only by the temperature of the liquid, usually water. At sea level water boils at 212F or 100C, but with each 500’ increase above sea level, the boiling temperature lowers by just under 1F. In other words the higher you are, the lower the air pressure, and the lower the boiling point becomes.
Equipment
All that is required is a heavy-bottomed pot or saucepan, with a lid, to evenly distribute the heat.
Boiling Process
Boiling can change food. For example, from wikipedia again: boiling toughens albumin in eggs making soft or hard boiled eggs, softens the fiber and dissolves connective tissues in meat, and softens cellulose in cereals, vegetables, and fruits.
Boiling makes certain foods palatable and edible by making them soft.
I boil pasta, potatoes, cereal (corn, oats), grains (barley, faro) , seeds (quinoa, rice), legumes (lentils, beans), etc. I do not boil meat often, as my experience is that it turns meat tough and uninteresting flavor-wise. However, I do boil meat bones to make bone broth and do poach chicken sometimes.
- Start cold water: Par-blanching or parboiling consists of immersing food in cold water first and then bringing the water up slowly to a simmer or boil. This way of boiling works for making boiled eggs (in the shell), and as a much noted “rule of thumb” is good for veggies that grow underground. Food that I boil and start by adding them to cold water includes: turnips, potatoes, or celery root that I am going to mash (as in mashed potatoes).
- Boiled Eggs: My best advice is to place eggs in a pot of cool water, enough water to cover them by 1″. Cover and bring water to a boil, then remove from the heat after it has cooked and let it sit fo ~10 minutes, and them move to cool water.
- Bone Broth: Using bones from the butcher, or left overs from dinner, combine with water and boil/simmer in a full pot of water. The goal is to leach all the goodness from the meat/bones into the water to create a broth to be used in other cooking. Common bone broth are created from beef, pork, chicken, and turkey. Fish broth can be made as well.
- Start in boiling water: The “rule of thumb” I have seen written all over the place is this is best for “veggies that grow above the ground.” Food that I put into already boiling water are: corn on the cob, as generally I do not boil veggies.
- Pasta: I heat the water to a boil, add salt, then wait for a full boil again before adding the pasta. Generally, I use 1 quart water for each 1/4# of pasta.
- “Instant” noodles and prepared foods
Maintaining a Boil
There are tricks to maintaining a boil. First, start with a pot that contains plenty of water. This is so when food is added, it does not cool the boiling water down too dramatically and slow the cooking process. Second, is to add food a little bit at a time, which allows the water to adjust and better maintain its heat. Finally, the third trick is to keep the lid on the pot, to maintain the temp.
Boiling Techniques
Boiling
A liquid in full bubble motion at 212F/100C where I live, since I am at sea level. Higher elevations water should boil at lower temps.
Blanching
Blanching cooks quickly, yet the foods retain flavor, the bright color is a hallmark of blanching. If cooked at a simmer or boiled, certain veggies (broccoli, green beans, spinach) would dull and texture would be lost.
- Prep the veggies to blanch
- Blanching then starts with boiling salted water
- Put veggies in the water until soft (a few seconds to minutes)
- Using a “spider” remove the veggies from the water
- Place on a cooling rack that is in a baking sheet to drain and cool off
- The food will not be cooked all the way through so will retain a bit of crunch
- Some blanched foods will be followed by being sauted, like carrots. I use this to cook frozen peas or corn, as they just need to be heated up.
To instantly stop all cooking after blanching, dip the cooked veggies into an ice water bath. I tend not to do this as I blanch quickly and let the food continue cooking while drying on the rack, thus keeping the food warm an cooked, ready for serving.
Boil for Reductions
Boiling causes speedy water evaporation, a useful sauce reduction effect where the liquid reduces and flavor concentrates.
- Reducing starts by heating a sauce at a simmer or slight boil.
- Stir occasionally to gauge doneness, but the idea is to let water evaporate from the sauce.
- What will be left is a concentrated form of the base sauce, thickened and concentrated.
- Some recipes will state a percentage reduction, like “reduce by 50%” to help guide how much reduction you should do.
Poaching
Cooking in enough liquid to cover the food, heated to ~180F/82C or less, the liquid will be hot but if there are bubbles they will occur occasionally, usually around the perimeter of the water, or be very small.
Poaching is a very low liquid cooking process that will not break delicate food apart. Great for delicate fish and poached eggs.
Scalding
You heat water near boiling 185F (85C) using a double boiler, the heat from the pan with water heats up the pan nestled in the pot, resting on the water. Thus, cooking without having the food touch the heated water. This technique is often used to prepare milk for breads and custards. (Some breads call for scalding milk, that then has to reduce to ~80F before adding to dough.)
These days when asked for scald milk, I just heat it up in the microwave to the point it gets a skin forming on top of the liquid.
Simmering
The liquid will be in motion, but have minimal bubbles at ~185–200F/85–93C.
To simmer food is to have a slow, under a boil, cooking. For grits, I bring salted water to a boil, add the grits and then lower the heat to a simmer to cook. Same for other grains and cereals.
Sous Vide
Sous vide cooking is the process of sealing food in an airtight container (a vacuum sealed plastic bag), and then later cooking that food in temperature-controlled water. There is a sous vide machine, that uses a heated metal coil to warm water to a constant temperature. Key to this cooking technique is that the heat never fluctuates to either high or low extremes. This cooking process is often described as gradual and controlled which means it takes a long time to cook, but is always good.
After cooking, the plastic bag is cut and the food removed onto the plate, unless it is meat. The meat will most likely need to be seared in a cast iron pan, so there is both color and a crisp caramelized flavor.
Stewing
This technique is similar to braising but is a wet cooking process also similar to boiling food; although it is more of a slow cooking simmer. This is a way to cook food in liquid (usually water or broth); where the meats and veggies in the stew are chunky in size, not diced or minced.
Wikipedia: A stew is a combination of solid food ingredients that have been cooked in liquid and served in the resultant gravy. Ingredients in a stew can include any combination of vegetables and may include meat, especially tougher meats suitable for slow-cooking, such as beef, pork, lamb, poultry, sausages, and seafood.
Velveting
Velveting chicken (often white breast) is a Chinese technique for chicken that is first cooked in boiled water for ~3-4 minutes, before chopping and using that chicken in stir-fry dishes. The gives chicken breasts an opaque look, with a “velvet” texture that is both tender and juicy. Further, this meat seems to never dry out, even as it gets cooked again.
I have only used this technique with chicken and water, but I have read you can do this with oil as well. Also I have done it with “clean” chicken breasts or tenders (no seasoning, skin, or bone), but have also boiled the meat after coating the chicken in a mixture of egg white, cornstarch, and rice vinegar. I liked them both, but give each a try to see what you prefer.
Why Boiling Can be Bad
Nutrients Get Lost
How we cook alters the nutrients in our food.
Healthline: Boiling reduces vitamin C more than any other cooking method. Broccoli, spinach and lettuce may lose up to 50% or more of their vitamin C when boiled. Because vitamin C is water-soluble and sensitive to heat, it can leach out of vegetables when they’re immersed in hot water.
The following nutrients are often reported as loosing their impact when boiled:
- Water-soluble vitamins: vitamin C and thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), folic acid (B9), and cobalamin (B12).
- Fat-soluble vitamins: vitamins A, D, E, and K.
- Minerals: primarily potassium, magnesium, sodium, and calcium.
Horrible if Overcooked
Over cooked boiled food is downright awful. Mushy, water logged, and hard to save. I hate to say this, but often in buffets in the Southern USA is where I have run into over-boiled veggies.
Why Boiling Can be Good
Makes Food Edible + Nutritious
Things like raw potatoes, sweet potatoes, yams, etc. are not edible raw, and really need to be cooked. Boiling is one of the better ways to prep root vegetables for consumption.
Boiling breaks down plants’ cell walls, that then releases more nutrients. Cooked, as opposed to raw, vegetables supply more antioxidants, including beta-carotene, lutein and lycopene. Steaming is better than boiling in terms of nutrient retention with no added oils or fats. The key however is that you use the water the veggies were cooked in (1), such as in stews or soups.
So if I boil potatoes, I may keep the potato water and use that with some homemade broth to make a soup or stew so nothing is lost from the pre-cooked food.
Boiling is Easy + Quick
Nearly anyone can boil water, you just put water in a pot on the stove, turn the burner on, and wait for the water to boil. Many instant foods just require this skill, so around the world instant, processed foods that just require boiling water is a life saving event during famine, catastrophes, and other calamitous events.
- What makes Instant Noodles so easy and quick is that all it needs is boiling water. The steps are simple: put 2C water in a pot, boil water, add noodles and packets, stir and let cook ~3 minutes, then eat. The act of boiling water is something everyone can do with a heat source, a pot with a lid, and water.
Low Calorie + Easy Digestion
Boiling food does not require oil or fats so are often low cal. Current studies indicate that boiling food is healthier than frying that food, even if fried in olive oil (2015, 1).
Boiled potatoes are less calories than butter fried potatoes, but mashed potatoes are often topped with goodies that turn them into fatty, salty, and high caloric meals.
Boiled food (and steamed food as well) are easier to digest than other forms of cooking as the food has started to break down before you eat it (2), so is a great food to feed people with digestion issues.
Kills Germs + Has No Mallard Reaction
Since boiling generally kills all the germs, it is safe to eat boiled foods. Killing those critters also means there should be less stomach inflammation if you are sensitive, or your stomach is reactive to critters.
The Maillard Reaction (a nonenzymatic browning reaction) is known to create a carcinogen called AcrylamidedH, something that boiling food cannot create (3). Thus, boiling food is a safer style of cooking.
Reduces Oxalates
The numbers I saw was boiling can reduce food’s oxalates by 30% to 87%, so might reduce kidney stone occurrences (4).
My Take
All cooking techniques have positive and negative effects, either in terms of nutrition, calories, carbs, etc. According to Nestle Professional (2006), some of these cooking techniques can be ranked by vitamin loss. So below is their list, from worst to best:
- Boiling (35% to 60% loss)
- Roasting (10% to 47% loss)
- Steaming (10% to 25% loss)
- Stewing, grilling, and baking (10% to 12% loss)
- Microwave cooking (5% to 25% loss)
- Frying (7% to 10% loss)
- Pressure cooking (5% to 10% loss)
Here are some tips to have your boiled food retain as many nutrients as it can:
- Try to serve the food as soon as it is ready, nutrients can be lost in the process of maintaining heat (keeping the food warm)
- Boil the food only until it is done, not melting.
- Add herbs (thyme for VitC) or citrus to boiled food to add back some nutrients.
- Use olive oil if fat is needed for the dish you are making.
- Either use or freeze the nutrient water after boiling for later reuse.
—Patty
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