In the kitchen, we’re much more familiar with acids than we are with alkaline ingredients. Acids include vinegar, lemon juice—all kinds of things that we use to brighten foods or add sourness. Acid ingredients are also found in everyday fermented foods, like yogurt. Alkalinity’s a little more unusual.
We generally only encounter it as baking soda, which is something that we use to balance acidity and to generate bubbles when we’re baking, but not something that we add with a free hand to our everyday foods. So let’s start at the beginning. Alkalinity is the opposite of acidity—it has to do with the nature of water. Water can be broken into hydrogen ions (H+) and hydroxide ions (OH−). Acidic ingredients are those that, when mixed with water, leave more hydrogen ions than hydroxide ions in a water solution. Alkaline ingredients are the reverse: they leave you with fewer hydrogen ions and more hydroxide ions. As obtuse as that sounds, it matters because most foods have a lot of water in them—in general, they are mostly water—and the balance between hydrogen ions and hydroxide ions makes a big difference in the way the other components of the food behave. Carbohydrates, proteins, and fats are all very sensitive to their chemical environment.
In Central America, the people who domesticated maize discovered that that grain was more easily hulled and more nutritious when it was precooked in water containing seashells or wood ashes—alkaline materials. So corn was treated with alkaline water very early on in American culture to get the grain out of the seed coat and to make it easier to handle.
The alkaline treatment of corn is what creates that corn-chip smell, the true tortilla aroma that’s unmistakable in a Mexican restaurant. Polenta, which is that same corn, though not treated with an alkaline ingredient, doesn’t have anything like the aroma of masa and corn chips and tortillas and all the things that come out of alkaline-treated corn from the New World.
One other very good example of the difference between alkalinity and acidity in cooking is in browning reactions. Acidic conditions make browning very difficult. Think about sourdough bread. It’s sour because there’s a lot of acidity. But sourdough breads just don’t brown very well in the oven. So the sour flavor may be wonderful, but it’s really hard to get a nice brown-colored, flavorful crust. Whereas if you use just a little bit of alkalinity to make a soaking fluid for, say, pretzels, you get that amazing brown crust. Pretzels are cooked for a very short time, and it’s normally very difficult to get a lot of browning to take place in a short time. But if you soak or boil the pretzels briefly in alkaline water before baking them, they brown much faster.
So why add alkaline ingredients to noodle doughs? Unless you’re going to fry the noodles, browning isn’t an issue. Why would you bother? Well, it turns out that adding alkaline ingredients has a significant effect on the texture, color, and flavor of the noodle.
By changing the chemical environment of the dough, the components in the flour change their behavior, and they change in various desirable ways. The color changes, because pigments in the flour that are ordinarily invisible become visible under alkaline conditions and take on a yellow hue. The interaction of the gluten proteins (which create the solid structure of the noodle) are also changed in such a way that the noodles become firmer. This is not that well understood, but apparently the bonding between gluten molecules becomes stronger under alkaline conditions.
And finally, there’s the effect on flavor. The flavor of alkaline noodles is really distinctive, and that’s as big a mystery as anything. Flavor’s the thing that gives us the most pleasure in food, and it’s also the aspect of food that we know the least about. Something happens when you cook alkaline noodles that creates a flavor that’s unique and pleasant. We know the taste of acidity—its sourness, its tartness. Alkalinity is harder to register, but it’s a kind of slick feeling in your mouth. If you take just a bit of baking soda and mix it with water and then put a drop of that on your tongue, you’ll see what I mean. It’s a little bitter, but mostly it’s a soapy kind of feeling. The more alkaline ingredients you include in a dough, the more you end up with that kind of slick, soapy feeling. (Past a certain point, that begins to get sort of unpleasant.) And the aroma gets eggier and eggier, too, which is weird in a noodle recipe that has no eggs whatsoever.
Alkaline noodles work so well in Asian soups because these very same qualities that make them different from ordinary noodles are qualities that make them especially useful in hot liquids. If the noodles are going to be immersed in liquid, they’re going to disappear unless they have some kind of distinctive character of their own, both in color and in flavor. The alkaline treatment heightens both.
But maybe even more important than those two elements is the effect that alkalinity has on the texture of the noodle. If you take an ordinary noodle and put it in hot liquid, eventually it’s going to dissolve, because the proteins are going to fall apart. That happens much more slowly with an alkaline noodle.
I’ve been curious as to how it was that alkaline noodles first came into existence. I’ve tried to find out and it’s just not clear. It seems that the first written records of alkaline noodles come from southern China. The speculation is that because the weather is much more hot and humid down there than it is in other noodle-making parts of China, the addition of alkaline ingredients might have begun as a way of helping the noodles stay fresher longer. If you make a dough in warm conditions, it’ll eventually turn into a sourdough. One way to compensate for that is to add unacid, an alkaline ingredient, to counteract whatever acidity might develop. But that’s a guess; we don’t really know for sure. We just know that noodles with alkaline ingredients tend to come from southern China, and have lived on past the point of our needing to protect against the acidification of the dough.
As for the particular alkaline ingredients that are added to noodles, Chinese and Asian alkaline noodles, in general, contain potassium and sodium carbonate, which are not the sort of things that we usually have lying around in our kitchens. They’re carbonate salts of those metals, sodium and potassium. They’re standard ingredients in Asia but not so much in the West.
However, you can easily make your own version of them by taking baking soda and baking it at a low temperature—200°, 250°F—for about an hour. You take baking soda, sodium bicarbonate, and turn it into sodium carbonate just by that gentle heat. Now, that leaves out potassium carbonate, but I’ve found that when I’ve experimented with it, simply using sodium carbonate gives you most of the effect that you’re looking for in an alkaline noodle.
The standard, industrially, is for about 1 percent of the weight of the flour to be the weight of the alkaline salt—the sodium carbonate or the potassium carbonate. I’ve found (and the industrial literature says) that if you go much beyond that the dough gets much more difficult to form, and it also just develops a very, very strong flavor—you really taste the alkalinity. Even with the right amount of alkaline salts, making the dough for alkaline noodles is something that I initially found very difficult, because the noodles are stiffer. But I came up with a couple of tricks that actually ended up making it really simple. What I found was that you can really take advantage of basic kitchen equipment to make your life much easier, and I don’t even try to knead it by hand anymore.
What I do is mix the water, the alkaline salt, and the flour in a food processor. I end up with something that’s almost like sand. There’s not quite enough water to make it into a proper dough in the processor. You take the sandy mixture out and compact it into a dough without actually working it. Then you use a pasta roller to develop the dough. Just run it through the rollers several times. I came up with that idea by looking in the technical literature about how alkaline noodles are made commercially. That’s basically how it’s done; they use very little water, they make a sandy kind of mixture to begin with, and then they just start sheeting it, which is a very easy thing to replicate at home with a pasta machine.