Thereâs a whole world of starches out there, from rice starch and cornstarch to mung bean starch and beyond. And yet of all the starches we might use, I think potato starch doesnât get nearly enough love.
Sure, potato starch has its fans. For those who keep kosher, itâs a popular alternative to wheat flour during Passover; itâs also popular among gluten-free or vegan bakers. But potato starch shouldnât be an ingredient you stash in the back of your cupboard, one you pull out just for holidays or the occasional gluten-free blondie. Iâd argue that you should stash it toward the front of your cupboard, since itâs versatile, quite useful, and it has some unique properties that distinguish it from the other starches out there.
In order to make the case for potato starch, I developed three recipes that illustrate the many ways in which it can be used: a potato starch riff on Japanese agemochi; a cold potato starch noodle dish; and a crispy, batter-fried chicken. Hopefully, these recipes will change some hearts and minds. But before we get to the recipes, letâs go over what potato starch is, and why it can do what it does.
Starch: A Definition
Starch is a polysaccharideâa long chain of carbohydratesâthat occurs in all kinds of plants; it forms a substantial portion of the human diet. Starches can be native (naturally occurring without much processing) or derived (chemically extracted or synthesized). Starch is abundant in staple plants like wheat, corn, cassava, rice, and mung beans, and itâs key to the textures of foods like bread, cereal, rice, and noodles.
For more concentrated, commercial forms of starch, we have all kinds of options. Hereâs a list (which is by no means exhaustive):
- Wheat starch
- Tapioca starch
- Potato starch
- Arrowroot starch
- Sweet rice flour
- Sweet potato starch
- Barley starch
- Mung bean starch
- Sago starch
- Kudzu starch
Common Uses for Starch in Cooking
Cooks use starches all the time in both obvious and not-so-obvious ways. Bread, pastries, pasta, noodles, and tortillas are some of the more obvious foods that use starches. In these examples, starches are typically used in their native state, as relatively unrefined cereal grain flours.
But we also use concentrated starch additives like cornstarch all the time, and theyâre primarily used to improve the textures of the foods we eat. We use them to thicken things like sauces, soups and stews, puddings, pastry cream, and even salad dressing. We also use starches to improve the texture of baked and fried goods, like alfajores and fried chicken.
How Starch Works
Starch exists as semi-crystalline granules. If exposed to sufficient heat and moisture, these starch granules swell and soften, losing their hard, crystalline structure, in a process known as gelatinization. The starch granules eventually burst, leaching starch molecules out into the water that surrounds them, and the mixture thickens. If that same mixture is cooled, the mixture generally becomes thicker, even rubbery at the extremes.Â Â
Key Players: Amylose and Amylopectin
All starches consist of amylose and/or amylopectin, which are large carbohydrate units of glucose molecules. Amylose takes the form of a relatively straight chain, while amylopectin is highly branched, and those structural differences lead to some different behaviors in cooking. Amylose isnât as soluble in cold water and it doesnât readily form a gel or produce a thickening effect until itâs heated; in contrast, amylopectin is more water soluble and, when dissolved, raises the viscosity of the surrounding water even at temperatures as low as 140Â°F (60Â°C).
The relative proportion of amylose to amylopectin in a given starch will dictate its behavior. For example, if our goal is to thicken a liquid with the addition of some kind of starch, weâd turn to starch sources with a relatively high amylopectin content if weâre looking to maximize thickening power. Thatâs because the larger, branched structure of amylopectin is better at raising viscosity. The tradeoff? The resulting gel doesnât have as much strength. A mixture thickened with pure amylopectin might be stringy or slimy, despite being the right âthickness.â If our goal is to have a more stable, firmer gel, then we might choose a starch with relatively high amylose content. Amylose has a linear structure and is tightly bonded, so it generally takes higher temperatures to break those bonds in order to thicken its surrounding liquid. Once those molecules reassociate into linear chains, the resulting gel is quite firm. So a pudding thickened with pure amylose might be excessively firm and brittle (like firm jello).
Whatâs So Special About Potato Starch?
Potato starch is a native starch extracted by crushing potatoes, which release free starch in the form of a milky liquid. The starch is washed out, collected, then dried to a fine white powder thatâs odorless and tasteless. Compared to a more mainstream starch like cornstarch, potato starch has a slightly lower amylose content (22 percent, versus 25 percent in cornstarch). Unlike cornstarch, however, this starch has a significantly larger granule size than any other starch: Up to 100Î¼m, compared to just 10Î¼m in cornstarch. (Starch granules can vary in size depending on the starch source. For example, rice starch granules range from 2 to 7âÎ¼m (microns), while wheat starch granules range from 6 to 25Î¼m in diameter.) This difference in granule size has some interesting implications in cooking, as weâll see.Â
For the purposes of this article, Iâll be referring to unmodified potato starch exclusively; unmodified potato starch is what youâd typically find in the grocery store). Modified potato starchâas well as other modified starchesâis starch that has been chemically or enzymatically treated to alter its cooking properties, making it more heat stable, tolerant to changes in pH, or more likely to produce some other textural behavior.
Potato Starch vs. Potato Flour
Are potato starch and potato flour the same thing? Short answer: No.
While potato starch is a pure starch extracted from potatoes, potato flour is made by cooking, drying, and grinding whole, peeled potatoes to a fine, off-white powder. As a result, potato flour contains fiber, protein, and, most notably, a distinct potato flavor. While potato flour does have some of the cooking qualities of potato starch, itâs not a pure starch, so its gelatinization properties arenât as robust. Because of its overt flavor, potato flour is often used in potato-based recipes. Itâs also commonly used to tenderize breads and pastries.Â
Uses for Potato Starch
Letâs look at some of the ways you can use potato starch, and some reasons why it might be a better (or worse) choice than other starches. For the sake of comparison, Iâll use cornstarch as a benchmark, since thatâs the starch most home cooks are familiar with.
Potato starch shares a number of similarities with cornstarch. When heated in water, potato starch behaves roughly the same as cornstarch: The starch solution starts off opaque, thickens, then forms a gel. In order to form a gel that doesnât have clumps, potato starch, like cornstarch, has to be dispersed in cold water before heating.*
However, potato starch has some advantages over cornstarch. For one thing, potato starch readily combines with water. In science terms, potato starch is said to have a high water-binding capacity, and its water binding-capacity is even higher than that of cornstarch. Also, gels made from potato starch solutions tend to be clearer and more neutral tasting than gels made from cornstarch (cornstarch often has a residual starchy flavor if not cooked out fully**). Finally, a sauce thickened with potato starch tends to be glossier and silkier, since potato starch has a lower lipid and protein profile than cornstarch, and as a result itâs a purer starch (this is also why its flavor is said to be slightly cleaner).Â
*Fun fact: Like cornstarch, at a ratio of roughly 2 parts starch to 1 part water, potato starch can form a funky non-Newtonian liquid known as oobleck.
**For certain desserts and sauces, clarity is important from a visual standpoint. This study shows that potato starch transmits almost 96% of light, higher than any other starch in question. The authors suggest that due to its large granule size, as well as its unique structure, potato starch pastes scatter less light, resulting in higher clarity.
Potato starch has a lower gelatinization temperature (140â149Â°F/60â65Â°C) than cornstarch (144â162Â°F/62â72Â°C), so it tends to thicken liquids faster than cornstarch when heat is applied. At the same time, it tolerates higher temperatures over short periods of cooking than cornstarch. And yet, potato starch is less heat stable over a longer time scale than cornstarch; prolonged heating tends to degrade its thickening power (although the same is true of cornstarch, if heated for an even longer period of time). As a result, itâs best to introduce potato starch as a thickener toward the end of cooking and, at the very least, itâs wise not to subject potato starch to long periods of boiling or the mixture itâs been used to thicken may begin to thin.
Like many starches, potato starch has limited pH tolerance. Acidic mixtures (think berry, citrus, or tomato sauces) tend to decrease its thickening power. But that isnât to say the thickening power goes to zero; you just might have to use more starch to achieve the intended texture.
Gelling, Retrogradation, and Stability
If you mix potato starch in water and heat it up, a clear, thickened gel forms. But what happens as the gel cools? For cornstarch solutions, the mixture tends to thicken further as it cools to room temperature. The same is true of potato starch solutions, though the effect isnât as pronounced. In both cases, whatâs happening is that the starch granules begin to reassociate as the mixtures cool, but because potato starch has a lower amylose content and larger granule size, itâs slightly more difficult for its relatively fewer, larger starch granules to reassociate.
That reassociation during cooling is called retrogradation. If you let a gel cool completely, like a container of cornstarch-thickened sauce in the fridge, you might notice it turns into a firm, opaque block, which is the result of the starch molecules reassociating and falling into a crystalline structure. In some cases, the sauce may even split or loosen in the fridge, forming a watery layer. This âweepingâ is known as syneresis, and it occurs when the retrogradation of the starch forces out excess water. Syneresis is exacerbated when a mixture is frozen and thawed. Sauces thickened with potato starch tend to retrograde less and resist syneresis, retaining their uniform, glossy texture when cooled, even if theyâre cooled to freezing temperatures and subsequently thawed. Plus, when cooled, potato starch sauces donât tend to form stiff, brittle gels, but rather viscous, translucent mixtures that flow. For this reason, potato starch is a great option if you intend to store your sauces for longer term use.
Pasting and Dough Quality
The thickening properties of potato starch are integral to understanding its application in doughs. Pasting refers to the increased viscosity of the surrounding liquid through agitation after the gelatinization of starch granules. In other words, when used in the right proportion, gelatinized potato starch can help form a cohesive dough that binds water very efficiently.
To test this idea, I compared two doughs mixed at 80 percent hydration: One made with all wheat flour, the other made with 100 percent potato starch. I made sure to gelatinize roughly 30 percent of each starch by cooking a third of the dry starch in all of the water, then incorporating that mixture into the remaining dry starch. The result? The wheat-flour dough was still rough and sticky, while the potato starch dough was smooth, cohesive, and easy to handle right off the batâalmost like playdough.
What about combining wheat starch and potato starch? Including a small portion of gelatinized potato starch in a standard wheat flour dough makes it easier to handle, since it can bind more water than gelatinized wheat starch. This binding property improves shelf stability and inhibits staling in breadsâa big reason why potato rolls are so successful.Â Â
Crispness in Baked Goods
Used judiciously, potato starch functions similarly to cornstarch in baked goods like cookies and crackers: It improves crispness, and inhibits gluten formation in wheat flour formulations, resulting in a more delicate texture. But just like cornstarch, if you use too much, the baked product can end up dry and crumbly. Itâs best not to exceed 30% of the total dry-ingredient weight in potato starch.
Dredges, Batters, and Frying
Itâs no big secret that cornstarch is a useful tool for improving the texture of deep fried foods. Take Kenjiâs recipe for Southern fried chicken, for example. When added to a wheat flour dredge or batter, cornstarch makes the coating crispier, and a cornstarch-wheat flour dredge or batter will also retain that crispness for longer than wheat flour alone. âCornstarch adds moisture-absorbing capabilities to the breading without adding excess [gluten] protein,â Kenji says.
But letâs dig deeper. Deep frying is a complex cooking process that integrates several of the concepts weâve covered so far: Amylose-amylopectin content, gelatinization, and retrogradation. When chicken is in a moist, hot environmentâlike a hydrated dredge or batter thatâs being deep friedâstarch granules swell up, allowing the amylose units to move around and separate from one another. As water is evaporated during frying, these separate starch molecules lock into place, forming a rigid, brittle network with a porous, open structure thatâs crispy. Cornstarch is higher in amylose than wheat flour, so it is able to form more of this network, resulting in a crispier product.
While cornstarch produces a solid result, I think potato starch performs even better in some cases. Years ago, I compared several starches and their effect in fully hydrated wheat flour dredges when they constituted up to 40 percent of the total dry weight. In test after test, potato starch produced the crunchiest, most cohesive coatingâeven when compared to cornstarch. Cornstarch samples were slightly more brittle and delicate. Not only was the potato starch coating crispier, but the crispy coating remained crispy up to 2 hours longer at room temperature.
How do we explain this difference? Remember that cornstarch has a slightly higher (25 percent) amylose content than potato starch (22 percent). So the amylose explanation isnât the full story. Potato starch has the largest starch granules (up to 100 microns, compared to 5 to 20 microns for cornstarch). According to starch researcher Peter Trzasko, quoted in Food Product Design magazine, smaller starch molecules like cornstarch rapidly form a starch gel when exposed to moisture and heat. Larger molecules cohere but donât gel as readily: Starches like potato starch have a molecular weight so much higher than that of cornstarch that it actually makes it more difficult for the molecules to associate, says Trzasko. My guess is that water is more easily and thoroughly evaporated from a potato-starch dredge during frying, since itâs not trapped as much in a gel. The result is a denser coating with intense crunch. As a corollary explanation, this study suggests that granule size correlates positively with perception of crunch.
Finally, since potato starch is more resistant to retrogradation than cornstarch, it tends to stay crisp for longer.
Potato Starch Recipes
So how do you put all this knowledge to practice? Here are a few recipes that illustrate the concepts weâve covered to get you started.
Fried Potato Mochi
This fun recipe is almost 100 percent made with potato products. Itâs inspired by a casual snack you can find at Japanese grocery stores and konbini, part of a class of fried snacks called agemochi. While agemochi are typically made using joshinko, a type of Japanese rice flour, these are made with boiled potatoes and potato starch. The natural potato starch found in russet potatoes is bound with partially gelatinized potato starch, forming a cohesive dough that can be shaped and cut to size. Shallow frying these squares further gelatinizes the interior, while crisping and puffing up the exterior. The result is a contrast in textures: A crispy outside encasing the slightly chewy inside, which has plenty of potato flavor. As a bonus, I glaze the hot fried mochi in an intensely savory-sweet sauce thickened withâyou guessed itâpotato starch. The whole thing is neatly wrapped in nori for style points. But honestly, you can just dunk the potato mochi in sauce and get crazy.
Chewy Cold Sesame Noodles
Starch-based noodles are commonplace all over East Asiaâmung bean starch noodles, sweet potato starch noodles, and flat rice starch noodles are just a few examples. Many of these noodles are served cold, in the style of Sichuan liang pi or Korean japchae. These noodles are a riff on those styles, and theyâre chewy, slippery, and illustrate gelatinization and retrogradation at work.
As it turns out, adding potato starch to a wheat flour noodle dough does some weird things: In high enough increments, potato starch increases the water absorption of the dough, reduces elasticity, and inhibits gluten formation almost completely in some cases; at the same time, it increases the springiness of cooked noodles, making them chewier; finally, the noodles are smoother, almost slippery, and more uniform in color than traditional wheat flour noodles. The best part? These noodles come together in less than 20 minutesâno real kneading, resting, or serious hand skills required. Theyâre served simply, with some basic greens and an intense sesame dressing.
Iâm a big fan of batter-fried chicken. While you canât go wrong with Southern fried chicken, batter fried chicken is a cleaner, less intensive way to make fried chicken that doesnât require going back and forth from dry to wet (it also doesnât trash your frying oil and leave a bunch of sediment). A blend of wheat flour and potato starch forms the foundation of this batter, resulting in a crisp but substantial crust with plenty of staying power.
Thereâs A Whole Starchy World Out There
Potato starch can be a powerful tool in your pantryâwhether as a subtle thickener, or as the star player in a savory noodle dish. But itâs also worth noting that potato starch is just the tip of a rather large iceberg. Different starches have different functional properties, and are better suited to certain applications. Hopefully, this deep dive inspires you to discover those differences and to find those applications. Thatâs what makes cooking so fun: Thereâs a whole world to explore, a vast expanse of creative ways to use starch that, despite all those industry studies and peer-reviewed efforts, science hasnât quantified exactly.