Revolutionize Your Vegetable Cooking With This Simple Tweak

Cooking is chemistry, but too often we overlook one of its most powerful tools: pH. Yet pH is at play in so many of the foods we cook. We use acidic ingredients like tangy yogurt or buttermilk in marinades to tenderize meat, we add a pinch of alkaline baking soda to shrimp to keep them plump and juicy, we add cream of tartar to egg whites so they whip up into a more stable foam, and we squeeze lime juice onto fish to "cook" the flesh without heat. But what about vegetables? Most home cooks are unaware of it, but we can leverage pH to help cook vegetables faster, modulate their texture and appearance, and even improve their flavor.

Let’s break this discussion down into parts, guided by a simple premise: Raising or lowering the pH of a vegetable’s cooking environment (a pot of water, for instance) changes its final characteristics. And we can look at those characteristics from the perspectives of flavor, texture, and appearance.

Flavor

If we are discussing raising or lowering the pH of a vegetable’s cooking environment by adding a basic or acidic ingredient, we need to first acknowledge the impact this will have on the cooked vegetable's final flavor. It’s inevitable that cooking vegetables in an acidic environment will lead to some noticeable sourness, even if minor. And if you’re using acidic ingredients with distinct flavors, such as fruity lemon juice or an assertive apple cider vinegar, the vegetable you're cooking will unavoidably take on that specific flavor, whether lemony or apple-cider-y or something else. The impact on flavor, it's safe to say, will be a major factor for selecting which acid you want to use when cooking vegetables.

On the other end, cooking in an alkaline environment will lead to some level of soapy/chemical flavor—think of the flavor of pancakes with too much baking soda in them. The degree of this off flavor will depend of course on the amount of the alkaline ingredient you use, but also which alkaline ingredient you use. For example, baking soda has a less caustic flavor impact than say ammonium bicarbonate (baker’s ammonia), calcium oxide (quicklime), or lye (sodium hydroxide), which are more concentrated basic ingredients.

Really, the effect on flavor when manipulating a vegetable’s cooking environment is unavoidable. Whether or not it’s a problem really comes down to personal taste and sensitivity to these flavors, and also consideration around how the vegetables are going to be served: If there's a bright vinaigrette for acid-blanched carrots, that tiny hit of acid on the carrots isn't going to matter. As for alkaline ingredients, it's often a balancing act—you’ll need to add enough of the base to get the desired softening effect, but using too much will leave a strong unwanted chemical taste in your mouth.

Texture: It’s All About Pectin

In general, lowering the pH of a vegetable’s cooking environment (that is, making it more acidic) leads to a tougher, hardier exterior, while raising pH (making it more basic) softens or even breaks apart the exterior. Why? It all has to do with pectin, the polysaccharide found in the cell walls of all land plants. Pectin’s primary functions are to facilitate cell adhesion and cell wall hydration, and to control the degree of cell wall porosity. If cellulose molecules are the bricks of a plant cell wall, then pectin is the cement (or glue) that holds those bricks together.

Pectin is sensitive to changes in pH. In an alkaline, high-pH cooking environment (say, greater than 8.0), pectin breaks down and dissolves more quickly, leading to mushier, softer textures as the cell walls fall apart more readily. In an acidic, low-pH cooking environment (around 6.0 or lower), that rate of breakdown slows dramatically, so vegetables retain more of their shape, crispness, and even crunch throughout the cooking process.

Understanding the effects of pH on a vegetable's texture can lead to powerful results in the kitchen. Let's look at some specific examples.

Some of the best examples of pH at work come from cooking potatoes. Take Kenji’s extra-crunchy potato chips recipe, where a sneaky addition of vinegar to the cooking water helps the potatoes retain their shape and firmness. Conversely, in Kenji’s crispy roast potatoes recipe, raising the pH of the cooking water with baking soda helps the exteriors of the potatoes break down more, creating a starchy slurry that leads to an extra-crisp coating encapsulating a fluffy interior.

How does changing pH affect the texture of other vegetables? For example, soaking and cooking dried beans in a solution of baking soda is common practice. The baking soda raises pH and displaces calcium in pectin (more on that later), softening the tough pectin shell.

What about vegetables like broccoli or green beans, or even carrots? We’d expect similar results: Tougher, more toothsome textures at lower pH values, and softer, more broken down textures at higher pH values. I set up some simple tests to verify this idea.

I cooked vegetables in three different solutions of 5-percent saltwater for 10 minutes each: a low-pH solution mixed with distilled white vinegar, a high-pH solution mixed with baking soda, and a neutral ‘control’ solution with nothing added. Here’s what happened.

Potatoes

There’s a notable difference in textures here. On the left, the low-pH samples showed virtually no deformation, and were almost crunchy when I bit into them. The control was what you’d expect of boiled potatoes: slightly broken down, a little fuzzy at the edges. But as pH rose above neutral, the exterior appeared fuzzier and fluffier, and the potatoes broke or mashed apart at the slightest manipulation. In informal cooking terms, these taters were “hammered.” 

Carrots

Once again, we see similar results to potatoes. Low-pH carrots looked pretty much raw—and ate that way. As pH increased above neutral, the carrots became much softer. The exteriors developed a fuzzy, brittle appearance. I could even mash the samples between my fingers. These carrots ate almost like baby food, requiring little to no chewing before they turned to mush. In other words, they’d be perfect for a smooth puree or sauce. 

Onions

The low-pH samples looked pristine—just barely cooked, with a noticeable snap when I bit into them. The neutral onions were softer, but still held their shape. On the extreme end, the high-pH onions were complete mush, devoid of any structure, and almost silky or jam-like in texture.

Key Takeaways for How pH Effects Vegetable Texture

• Lowering the pH of a cooking solution with an acid tends to yield more toothsome vegetables that retain their shape throughout the cooking process; they also break down less readily.
• Raising the pH of a cooking solution with a base tends to result in softer, mushier vegetables with less structure; they break down more readily.

Appearance: Colors Matter

If pH has such an outsized effect on the texture of cooked vegetables, it shouldn’t surprise us that it can change their appearance too. Take green vegetables like spinach or kale, for example. These vegetables are rich in chlorophyll, the pigment that gives plants and algae their green hue. In isolation, even in room temperature water, chlorophyll is sensitive to changes in pH: in the pH range of 2-5, it turns from green to olive green, even yellow; in the pH range of 6-13, chlorophyll stays vibrant green. That's at room temperature, so it's important to keep in mind that these results shift slightly when heat is introduced.

Chlorophyll isn’t the only pigment affected by pH. Take anthocyanins, for instance, the purple-red pigments found in red cabbage, red onions, and blueberries. In acidic conditions, anthocyanin turns a stark crimson red; in basic solutions, it turns violet to blue. In fact, red cabbage juice can often be used as a “quick and dirty” pH indicator for solutions because of how dramatically and reliably its color shifts in different pH environments.

Once again, I set up three different 5-percent saltwater solutions of varying pH ranges to cook the vegetables, and kept my eye on their color.

Broccoli

As expected, there were dramatic changes in color depending on the pH of the cooking solution. In a more acidic solution, broccoli turned an olive green, almost yellow. At neutral, the florets stayed green, but the stems took on a paler green. In a basic solution, the florets turned a vibrant green, and even the stems turned much greener than the neutral samples. 

Leek Tops

For the most part, I had similar results with leek tops. At low pH, the leeks were a dull gray-green, lime green at neutral, and deep vibrant green at high pH.

Snap Peas

Same story for snap peas. Note that even when cooked at higher pH, snap peas retained some of their crunch and did not turn mushy, a sign that their name is apt—they really do hold onto that snap. 

Red Cabbage

You can observe the striking difference in color. Note that at higher pH, there is a gradient from blue to purple at the interior, indicating incomplete penetration of the cooking solution over a 5-minute period. 

While these results are specific for a blanching/boiling environment, it's worth mentioning that in a baking/roasting environment, it’s likely there would also be enhanced Maillard reaction in an alkaline environment as well.

Key Takeaways for How pH Effects Vegetable Appearance

• As the pH of a cooking environment falls below 7.0 (more acidic):
• Green vegetables become olive green or even yellow.
• Anthocyanin-rich vegetables get redder.
• As the pH of a cooking environment rises above 7.0 (more basic):
• Green vegetables stay more green and vibrant.
• Anthocyanin-rich vegetables become violet or unnaturally blue.

Practical Tips: The Easiest Ways to Adjust pH

Ok, we’ve firmly established that pH matters when cooking vegetables. But how do we adjust pH in a practical way?

Lowering pH

The simplest way to lower the pH of water is to add an acid. You’ve got several options, but here are just a few:

Lemon Juice 

Chances are you’ve got a lemon or two hanging out in your fridge. And for centuries, cooks have relied on lemon juice for an instant shot of acidity. The downside? In order to lower the pH of say, a large pot of water, you might need to use a substantial amount of lemon juice. And depending on the recipe, that citrus flavor might come through in the finished product. 

Vinegar

If you don’t want that bright citrus flavor of lemon, then vinegar—any type will work, but especially distilled white vinegar—is a great alternative. Its acidity is roughly on par with lemon juice. Of course, you could opt for other vinegars like apple cider or rice wine vinegar, but I wouldn’t break out the fancy Banyuls or aged balsamic for this application.

Citric Acid Powder

Though it’s less common in the average pantry, citric acid powder might be one of the best ways to lower the pH of a solution. You can easily measure it to the gram, you don’t have to use too much in order to lower pH enough for the desired effect, and its flavor (other than sourness) is arguably less distinctive than lemon juice or most vinegars. 

Raising pH

There are multiple ways to raise the pH of a cooking solution to make it more alkaline.

Baking soda

Baking soda is, by far, the most common alkaline ingredient available in the average kitchen. It’s a mild alkali, which means it is relatively weak and safe to use in reasonable amounts compared to other pH-raising additives. And when it comes to vegetable cooking, in addition to raising pH of blanching water, baking soda does double duty: It further breaks down pectin by adding sodium to the water. Through a process known as a displacement reaction, sodium displaces calcium in pectin, weakening a vegetable’s cell structure. 

At first thought, using baking soda and ending up with mushy broccoli might seem like less favorable results. But using baking soda to raise the pH of a cooking environment can actually be very useful: You can shorten cooking times via the softening power of baking soda, retaining a brighter, less cooked flavor while still getting a cooked texture, and also locking in that bright green color. This is a major win for vibrant vegetable soups like my broccoli soup recipe, or sauces like in Sasha Marx’s creamy orecchiette recipe, or even the most basic of vegetable purees. 

Other alkali sources

Other, less common alkaline additives include a roster of food-safe alkali salts: sodium carbonate, potassium carbonate, potassium bicarbonate, ammonium bicarbonate (baker’s ammonia), calcium oxide (quicklime), and even sodium hydroxide (lye). 

Many of these additives are stronger than baking soda, sometimes caustic, and often have a pronounced bitter or soapy taste when used without discretion. So why use them at all? Well, sometimes you might need to raise the pH of a cooking environment far higher than baking soda might be able to (without using a concerning amount) such as when making Bavarian-style pretzels or alkaline noodles such as ramen noodles.

The Bottom Line

Here’s a quick-and-dirty breakdown of trends as pH increases or decreases for blanching vegetables.

As pH Falls Below 7.0 (more acidic):

• Vegetables tend to stay more toothsome or crisp, and retain their shape through cooking; it takes longer to cook them until tender.
• Green vegetables take on a dull green or pale yellow color.
• Anthocyanin-rich vegetables turn pink or crimson.

As pH Rises Above 7.0 (more basic):

• Vegetables tend to get softer and mushier, which may be ideal for mashes, purees, or sauces.
• Green vegetables become vibrant green.
• Anthocyanin-rich vegetables turn blue to violet.