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Why Do The Skins Come Off Beans? [& How To Prevent It From Happening]

Last weekend I spent hours cooking beans trying to recreate my moms famous bean salad. 

I opted for dry beans because they have more flavor. I wanted it to be the best bean salad anyone has ever tasted (really I just wanted it to be better than my mom’s).

As I lifted the lid off my pot of beans my heart sank. Most of the beans had split and the skins were floating around at the top. My bean salad was a disaster. 

I was determined to find out what happened and how I could stop it happening again.

So why do the skins come off beans?

The skin comes off beans because it’s too tough and can’t expand as fast as the inside of the bean. This leads to it bursting open. Older beans or soaking beans in hard water can lead to tough skin. To prevent the beans from splitting again soak them in saltwater.

Why are the skins falling off my beans?

The skins fall off your beans because the inside of the bean is expanding faster than the skin. Beans typically expand up to 2-3 times their original volume during rehydration. 

If the bean’s skin is too tough and it’s not stretching, then eventually the inside of the bean outgrows the skin. The skin bursts and falls off. 

Have you ever microwaved a milky bar? It’s the same kind of thing. (If you haven’t, stop reading, go and buy a milky bar, and try it.)

There are several reasons your beans skin could be too tough, although splitting can still happen even if none of these factors are at play. 

Water composition/bean skin structure

If you’re soaking or cooking your beans in hard water this can lead to extra hard skins.

Magnesium and calcium ions in the skin of the bean are responsible for keeping its structural integrity intact and preventing any breakages. 

beans in hard water vs soft water
Beans soaked in hard water can often become tough

In areas with hard water, there’s a higher concentration of magnesium and calcium in the water than normal. The minerals from the water soak into the bean and this can lead to extra-tough skins.

Age and type of bean

Any type of bean is susceptible to its skin falling off, but it’s more likely to happen with old beans.

The longer a bean has been dried for, the tougher and less pliable its skin is and the quicker it is to break. If your beans are splitting during soaking it’s likely that they’re too old.

There’s no way to know how old the beans you buy from the supermarket are, so it’s best to try and use them within a year. 

Bigger beans like cannellini or chickpeas tend to have firmer skin than more delicate beans like black beans and therefore are more prone to exploding. 

How to prevent the skins from falling off my beans

To stop the skins from falling off your beans you need to make the skins more stretchy.

How?

Thankfully it’s easier than making yourself more strechy (unless you’re a gymnast).

All you have to do is soak them in saltwater.

Soaking beans is a long-debated subject, but if you have a problem with exploding beans I definitely recommend it. It will help soften the skins and therefore stop them from breaking.

Follow these instructions to brine your beans (long soak method):

  • For every pound of beans add 3 tablespoons of table salt to 4 quarts of water (16 cups).
  • Stir the salt until it’s completely dissolved.
  • Soak the beans at room temperature for 8-24 hours. How long depends on the type of bean you’re using. You might notice the skin start to go wrinkly quite early on and look as it’s going to split. Don’t panic if you see this. It’s normal. After a while, the bean will fill out, and the skin will no longer look shriveled.
  • Drain and rinse the beans before cooking.
  • Add a pinch of salt to the cooking water and cook as normal.

If you’re pressed for time, you can also quick-soak your beans in the saltwater. This entails bringing the salted water to the boil before taking it off the heat and letting the beans soak for 1-2 hours.

For zero split beans long soaking is better because it’s more delicate.

How does salt soften the skin?

If I told my mum I was planning to soak my beans in saltwater she’d tell me I’m crazy.

In the past, the advice has always been to avoid salt until the beans are fully cooked because of the belief that salt will toughen the bean and increase the cooking time.

However, this has since been debunked by various different sources. Most notably by America’s test kitchen (see the video below).

If you run your own experiment (as I did, you can see the results later on) soaking some beans in saltwater and some not, you’d notice the salted beans develop a softer, more supple skin.

The softer skin can expand at the same rate as the inside of the bean during cooking and, therefore, stay intact. No more explosions!

The reason behind this is a pretty scientific so bear with me.

beans in plain water vs salted water
Beans in salt water absorb sodium ions which weakens the skin

I explained earlier that the bean’s skin contains magnesium and calcium ions (minerals). These ions help toughen the skin so it can do its job and protect the bean. 

The saltwater solution is full of sodium ions. 

During the soaking process, some of the minerals in the skin are replaced by sodium ions from the saltwater. 

Sodium ions have a weaker charge than magnesium and calcium ions, so their inclusion makes the skin more permeable. More water can soak into the skin, meaning it’s more able to expand and stretch. The extra water also gives the cooked beans a smoother and creamier texture.

The salt itself only affects the bean’s skin and not the inside. There’s no need to worry about over-salting your beans.

An alternative to salt is Kombu (amazon link). Kombu is a type of dried seaweed and contains both sodium and potassium ions. Like salt, these ions replace the minerals in the beans’ skin and make it more permeable to water. 

Kombu will also add umami flavor to your dish and tons of healthy nutrients such as iron and vitamin C.

According to Cook’s Illustrated, if you’re using kombu there’s no need to soak the beans. You can add it straight to the cooking water.

My experiment

I got my hands on some dried cannellini beans and decided to test soaking the beans in salted vs unsalted water myself.

I soaked the beans overnight. Half in salt water, and half in unsalted water.

Here are the beans in the morning (before cooking).

beans soaked in saltwater vs normal water
Soaking beans in saltwater helps to keep the skins on

As you can see there were slight differences already. The beans soaked in saltwater were all intact. The beans soaked in plain water were mostly intact, but a few had already started to lose their skins.

Then I cooked the beans.

beans soaked and cooked in either saltwater or unsalted water
Saltwater soaking and cooking produces the best beans with skins intact

It’s clear from the results that salted water soaking water and cooking water results in the most intact beans. While using plain water for soaking and cooking will leave you with a lot of loose skins.

Cooking technique

Rough cooking can also contribute to split beans. If the beans are constantly moving around and bumping into each other, they’re more likely to succumb to the pressure building up inside. 

Try not to boil the beans. A simmer is all that’s needed. Also, stir the beans gently and only when you need to. You can even consider cooking the beans in the oven to avoid any stirring.

If the skins are falling off after you’ve been cooking the beans for a while, it could be that you’re overcooking the beans. Test your beans every so often to see if they’re done.

Are the beans still okay to use without the skins?

Beans whose skins have fallen on are safe to eat and can be included in your final dish. But it isn’t ideal for the texture or aesthetics of the dish.

The skinless beans will cook quicker than the beans whose skins are still intact. They might end up pretty mushy. If only a small proportion of your beans have split, this isn’t really a problem. In fact, it can enhance the dish by thickening the sauce.

If most of your beans start splitting, this can lead to an overly mushy dish that isn’t very appetizing. You can salvage this situation by making a puree or soup.

The skinless beans will also affect the aesthetics of your dish.

Having exploded beans is less than desirable when you’re trying to make an Instagram-worthy (mum-worthy) bean salad or chili.

In this case, I’d pick out the offending beans.

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