How baking soda changes the color of cooked vegetables

HostI was steaming some broccoli the other day, and it went from that beautiful bright green to a sort of sad, muddy grey in what felt like seconds. It's one of those little kitchen letdowns we have all seen, but then I heard there's a way to stop it with just a pinch of something from the cupboard. Why does a tiny bit of baking soda make such a huge difference to how our greens look on the plate?

GuestIt's a pretty cool bit of kitchen chemistry. To understand it, you have to think about what makes a vegetable green in the first place. That green color comes from something called chlorophyll. You can think of it like a tiny, colorful ring with a bit of magnesium, which is a type of metal, sitting right in the middle. As long as that metal stays in the center, the plant looks bright green. But when you cook the vegetable, the cells start to break down and leak. Inside those cells are natural acids. When the acid hits the green parts, it swaps out that bit of metal for a bit of hydrogen. As soon as that swap happens, the bright green turns into that dull, muddy olive color you saw in your steamer.

HostSo the acid is basically the enemy of the green color. But how does a pinch of baking soda stop that swap from happening?

GuestWell, baking soda is what we call a base, which is the exact opposite of an acid. When you drop a little bit into your cooking water, it finds all those acid bits and cancels them out before they can attack the green color. It keeps the water slightly basic. Because the acid is busy dealing with the baking soda, it never gets a chance to kick the metal out of the green rings. The result is a green that's almost neon. It looks even brighter than it did when the vegetable was raw.

HostWait, if it makes the food look that much better, why are we not all doing this for every meal? It sounds like a simple fix for better looking food.

GuestThere's a pretty big catch when it comes to how the food feels in your mouth. You see, plants are held together by a kind of natural glue called pectin. This glue is what gives a carrot its crunch or a stalk of broccoli its snap. That glue is very sensitive to the water it's swimming in. If the water is a bit acidic, the glue stays tough. But baking soda is like a wrecking ball for that glue. It breaks down the walls of the plant cells much faster than plain water does. If you use even a tiny bit too much, or cook it for a minute too long, your vegetables will turn into a pile of mush. They lose all their bite and become sort of slimy.

HostSo it's a trade-off between having something that looks beautiful and something that actually has a good texture. Does it change anything else, or is it just about looks and mushiness?

GuestIt actually goes deeper than that. It messes with the good stuff inside the food, too. Many of the vitamins we need, like Vitamin C and some of the B vitamins, are very unstable. They don't do well in a basic environment. When you add baking soda to the water, you're basically speeding up the rate at which those vitamins break down. By the time you get that perfect bright green broccoli to the table, a lot of the actual health benefits might be gone. Plus, it can give the food a slightly soapy or bitter taste if you're not careful.

HostThat sounds like a lot of downsides just for a bit of color. But what about other vegetables? I have seen what happens when you cook red cabbage and it turns that weird blue color. Is that the same thing?

GuestIt's a similar idea but with a different color bit. Red cabbage and radishes have something called anthocyanins. These are like tiny mood rings for plants. They change color based on how much acid is around. In a very acidic environment, like if you add vinegar, they stay bright red or pink. But if you add baking soda and make the water basic, they shift. They go from red to purple, then to a strange blue, and if you keep going, they can even turn green or yellow. It's actually a bit of a shock the first time you see your red cabbage soup turn teal because of a little baking soda.

HostOkay, so it sounds like for most green or red vegetables, it's probably better to just leave the baking soda in the cupboard. Is there ever a time where it's actually a good idea to use it?

GuestThere are a few spots where it's a real lifesaver. If you're cooking dried beans or chickpeas, a pinch of soda can be a big help. Like I said, it breaks down that cellular glue. Since beans have very tough skins and walls, the soda helps them soften up much faster. It can cut your cooking time way down and give you a much creamier texture, which is great if you're making something like hummus. It's also why some people use a tiny bit when they're browning onions. It breaks the onions down so fast that they turn into a golden jam in half the time it usually takes.

HostSo it's less of a color booster and more of a tool for changing how fast things break apart.

GuestUsing a pinch of soda to soften old beans for a dip is probably the one time the trade-off is actually worth it.

HostThat head of broccoli might look like a painting, but it's really just a tug of war between the acid and the soda in the pot.