Why and When to Use Potato Starch in Baking (Tested Cakes, Cookies & Brownies)

It’s not the most common baking ingredient, but it shows up here and there. You might have come across it if you’re into baking cookies or cakes of a Northern European origin. Or, if you’re looking for gluten-free alternatives. It’s also not uncommon to see it as an ingredient in egg replacers.

What we’re talking about? Potato starch. And in this post, we’ll dive deep into where and when you can use it in baking!

What is potato starch?

After water, which makes up over 80% of a potato’s weight, starch is the most prevalent ingredient in potatoes. Starch is the energy reserve for when the potato gets planted and needs to grow into a new plant. It sits in the potato cells, as small granules. Each granule contains a lot of individual starch molecules, tightly packed together.

Potato starch powders are made by extracting that potato starch from the potato. It can contain a few other minor ingredients that are naturally present in the potato and get extracted out as well, but close to 100% is starch.

Starch is a large carbohydrate molecule, made up of long chains of glucose molecules. There are two main configurations of these glucose chains: amylopectin and amylose. How much is present of each of these depends on the potato variety as well as several other factors, and is important for how a potato cooks.

There’s a lot to learn about potato starch. We wrote in a lot more detail about how it’s made and what it is in a potato starch only post.

Role of potato starch in baking

You can use potato starch in a lot of different applications. For this post specifically, we’ll stick to using it to make baked goods such as cookies, cakes, or brownies.

Potato starch helps to ‘hold it all together’

To make a baked good like a cookie or a cake you need to transform a raw, uncooked batter/dough into a solid, cooked product. Quite a few transformations take place thanks to a range of ingredients working together, with each its own place and role. Some of the most common types of ingredients you’ll find in them are:

• Wet/liquid ingredients with water: to add moisture and flexibility (e.g. eggs, oat milk)
• Fatty liquid or solid ingredients: to add richness and flavor (e.g. oils, butter, lard)
• Sweetener: to sweeten the product, but possibly also to provide crunch or moistness and bulk (e.g. sugar, maple syrup)
• Leavening agents: provide airiness and lightness (e.g. baking soda, yeast)
• Texturizers/”Holding it all together“: if you just mix together the ingredients above and bake them, you won’t get a product that actually holds itself together. Instead, you need some ingredients that do this. This is where potato starch comes in!

Note, in our course on the science of cake we discuss the role of all of these individual ingredients in far greater detail!

Thickening

To look at the role of potato starch as “holding it all together” ingredient, we’ll have to look at those starch granules again. When you mix these granules (aka the starch) with water and heat this mixture up, the granules will start to absorb more and more of that water. As a result, they swell up and might even break, releasing all those individual starch molecules into the liquid. These can then absorb even more water. By absorbing and holding onto all that water, potato starch thickens liquids and batter.

Potato starch also contains high (compared to other starch types, it is still <0.1%) amounts of phosphorus. This phosphorus interacts with the starch, impacting how the starches swell and thicken. Generally speaking, higher amounts of phosphorus result in lower viscosity pastes compared to low amounts.

By holding onto that moisture once the starch is cooked, potato starch can also help to make a moist and tender baked good.

Potato starch has quite large granules, which is good for thickening. However, it also increases the risk of a not so smooth texture (this is especially relevant when making custards and puddings) and clumpiness. Also, potato starch granules are somewhat more fragile compared to e.g. corn and wheat starches. As a result, the granules break more easily. Too many broken granules can result in stringy and weak pastes.

Egg replacer ingredient

Since potato starch can bind water well, while still making a moist food, you will often find potato starch as an ingredient in egg replacer powders. These powders (as we tested in cakes) can replace egg in certain applications. They are often a blend of ingredients, every ingredient plays its own role. Potato starch by itself wouldn’t be able to replace egg. That is why manufactures blend it with other ingredients.

No network building gluten

Potato starch will thicken a liquid and form a ‘gel’, this is similar to the role of starch in wheat when baking. However, wheat flour, one of the most common baking ingredients, also contains gluten. Gluten are proteins that are very good at forming a large network. This network can then hold onto gas bubbles which is essential when baking a yeast-risen bread. Potato starch doesn’t have this more ‘advanced’ capability

Different crops give different starches

Potatoes aren’t the only type of produce that contains a large amount of starch. Rice, wheat, cassava, corn, and many more all contain starch. These starches are broken down in our body to supply us with glucose, an important source of energy for our bodies.

Starches from different crops, have different properties and won’t behave the exact same way. We’ve discussed some of that when looking at using starches as thickening agents. That said, if you don’t have one type, you can always try to replace it with another starch (with a few exceptions) and see whether it works. It might give a slightly different result, but still get pretty close since they are all based on that mix of amylose and amylopectin molecules.

Potato Starch vs. Corn Starch & Wheat Flour

When looking at how and when potato starch works, we have to compare potato starch with ingredients that fit in the same category. No use to compare potato starch with a sweetener or fat, we already know they have two very different roles!

As such, we’re focusing on comparing potato starch with other ingredients commonly used for a similar purpose: corn starch and wheat flour. Corn starch is most similar to potato starch. It’s also a starch, but made from corn instead of potato. Wheat flour is slightly different, it’s ground wheat but isn’t pure starch. Instead it also contains gluten proteins and various other carbohydrates aside from starch.

We compared potato starch with corn starch and wheat flour (a low gluten/cake flour variety) in three different applications: brownies, cake, and cookies. For each, we kept the overall quantity of ‘flour’ the same (we’re calling the starches flours as well for simplicity’s sake), simply exchanging one for the other. You can find the recipes we used at the bottom of this post.

What about potato flour?

Potato flour is different to potato starch seeing as how it contains all ingredients (except for the moisture) of a potato. The other proteins, fat, etc. in the flour make potato flour quite different from starch, also, it will have more of a potato-y flavor. Since potato starch is more commonly used as a wheat flour/corn starch replacer we decided to focus on those.

Brownies

Up first: brownies. In our brownie recipe less than 15w% was made of starch/flour. Instead, we hypothesize that eggs, which make up >20w% of the recipe take over a lot of the structuring roles. The role of the flour or starch would be smaller (though not completely insignificant of course). This would probably make the impact of changing out the flour types less significant.

The samples

We made three brownies that were identical, except for starch or flour it contained:

1. Potato starch
2. Corn starch
3. Wheat flour

Findings

The brownie batters looked almost identical. There was no way to distinguish the different recipes. Once baked, the three brownies were again very similar. If anything, the corn starch version was a little moister than the other two. That said, that one was baked in between the other two (a bit of an experimental design error) so that might well have been the cause. Also, we expect that different ‘flours’ might have had slightly different optimal baking times. As such, if you’d fine-tune those for each, we think you’d get three perfectly fine brownies which are hard to distinguish!

Overall though, all three made a well cooked brownie. Further tweaking could have made their tops more crispy, or their interiors more gooey. But that wasn’t necessarily influenced by the use or absence of corn starch.

Cake

Next up, cupcakes. We made a chocolate cupcake variety. Flour/starch plays a bigger role in these cupcakes than it did in the brownie (makes up >25%). As such, we were a little more cautious in replacing the wheat flour the recipe called for. We only replaced half of that with either potato or corn starch.

Findings

This time, we could see some clear differences. The 100% wheat flour batter was clearly thicker than the other two, which were still very similar. All cupcakes were baked on the same rack in the same oven and rotated midway. Nevertheless, we saw some clear differences in baking behavior. The potato starch cupcakes baked more quickly. When we took them out of the oven the potato starch variety was fully cooked, whereas in hindsight the other two were still slightly underdone. They collapsed a little (as you can see in the photo).

That said, you could optimize the baking times for each and create very similar tasting cupcakes. The differences in flavor and final texture were minor. Of course, only half of the flour was replaced by starch, which is why for the next test, cookies, we decided to go all-in!

Using potato starch in cookies

There’s a version of shortbread cookies in the Netherlands that’s called ‘sand cookies’. These cookies are supposed to be ‘sandy’ and break apart quite easily. Seeing how potato starch behaves, we decided those cookies would be a perfect testing ground for potato starch vs wheat flour. We made four different cookies, each with the same amount of butter and sugar. The last ingredient was (a mix of) starches a/o flour:

• 100% wheat flour
• 100% potato starch
• 50% wheat flour + 50% potato starch
• 50% wheat flour + 50% corn starch

Findings

Seeing as how these were very simple cookies with just three or four ingredients, of which the starch/flour made up more than half the overall recipe, we expected to see some effect. That was indeed the case! The raw doughs were noticeably different (see photo above). The dough that did not contain any wheat flour was very wet and sticky. The dough that only contained wheat flour showed the opposite effect, it was the driest and toughest of all.

After baking, the differences were even more apparent. The 100% potato starch cookies were very, very fragile. You could barely pick them up for fear of them falling apart. They had also spread most on the baking tray and had barely browned. The 100% wheat flour cookies were the opposite. They had spread out least, were driest to eat (so clearly has a higher water-binding capacity) and were the brownest of the bunch (probably due to the presence of sugars and protein in the flour).

The 50% corn starch and 50% potato starch fell somewhere in between on all these parameters. Interestingly, these were both most ‘sandy’, but in a positive way. So would be good candidates for a ‘sand cookie’.

What was interesting is that the corn starch cookie was the only ‘wrinkly’ cookie in the bunch. This tends to happen at a sweet spot where the dough is soft enough to expand slightly, but not soft enough to completely spread out. Cookies like this always expand a little because of the moisture in the butter that evaporates and the fat which melts (making the dough softer). The gas that is formed pushes itself outward. Decreasing the wheat flour content might result in a similar effect.

Side note: potato starch can be modified

These tests were all done with standard store-bought potato starch. Most stores just sell one type of potato starch: regular, unmodified potato starch. This is starch that is simply extracted from the potato, without been processed further. However, food manufacturers might well be using modified potato starch. This is potato starch that has been modified, e.g. by extra heating or chemical reactions to change how it behaves. These modifications are done to improve one or several aspects of the potato starch. For instance, the modification can change the viscosity of the gel that is formed or it can improve the heat resistance.

When testing potato starch, keep this in mind. If you’re testing for large-scale applications, contact your supplier on the type of potato starch they’d recommend. If you’re testing at home, keep in mind that what might work in a product you’ve bought, doesn’t translate directly to a kitchen application.

Conclusions on baking with Potato Starch

Potato starch is a dry ingredient that you can use in baking to help provide thickness and structure to the product. In the cookies, cake, and brownies we tested, it behaves similar to corn starch, however, it does have a slightly more sandy texture. Potato starch can replace wheat flour in instances where the role of flour to hold it all together isn’t too big. However, potato starch doesn’t bind a dough or batter together as well and so in some instances (e.g. cookies) can need some help from wheat flour to keep it all together.

Gluten-free brownies 🙂

Inadvertently we believe we ran into a great gluten-free brownie recipe here. Potato starch is free from gluten (unless processed on a line with gluten) and so using potato starch instead of wheat flour gives you a gluten-free brownie! We haven’t yet tested it with our black bean brownie or our cakey & gooey brownies, but think there’s a decent chance they’ll come out good!

Share your potato starch use!

Now that you know why and when you can use potato starch in baking, we’d love to hear how you use potato starch in your baking (or even in non-baking applications)! Are there specific instances where it works really well (or really bad)? We’d love to hear so we can build upon it.

References

Jaspreet Singh, Lovedeep Kaur, Advances in potato chemistry and technology, Academic Press, 2009, Chapter 10, link