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Cornstarch (Recipe: beef stir-fry with bitter melon)



Which pantry item starts out yellow, but ends up white and green?


Cornstarch -- a white powder ground from the endosperm of the yellow corn kernel. When cooked in a sauce or stir-fry, or baked in a pie, cornstarch turns clear. When manufactured into biodegradeable trash bags, it turns "green."

Fortunately, cornstarch doesn't turn food green!

Called corn flour in other parts of the world, cornstarch, a gluten-free thickening agent, was patented in 1841; though first used as a laundry starch, it's as popular today in the culinary arena.

I've been learning more all the time as I research my way through my pantry. Most often, for thickening stews and stir-fries, I'll reach for the arrowroot on my spice rack, but more recipes for baked goods call for cornstarch. I wondered why.

According to food science guru Harold McGee, "Arrowroot and potato starches come from below-ground storage organs, cornstarch and flour from seeds, and the two different kinds of sources produce starches with different qualities. Briefly, the root starches have larger granules and longer starch molecules that gelate and thicken at lower temperatures, and are more efficient at thickening, but that break down on prolonged heating or freezing: so you need less root starch to thicken, but the consistency isn’t as stable. Root starches also have a more neutral flavor than seed starches."

And from The Accidental Scientist I learned that too much of a good thing -- stirring -- can negate the thickening process. Generally cornstarch is added to a sauce in a slurry: i.e., mixed with a liquid (water, stock, etc.), to prevent lumps from forming. (Generally I use one tablespoon of cornstarch to three tablespoons of water.) Cornstarch begins to thicken when heated to 203°F, and it thickens quickly, turning from milky white opaque to transparent. After that point, stop stirring, as any agitation will interfere with the setting process. When the starch network that sets and traps the liquid is broken, liquid is released and thins the sauce.

If you're adding cornstarch to a sauce (or pie filling) and it does not thicken, try adding more liquid, not more cornstarch. Counterintuitive, I know, but the problem could be that there wasn't enough liquid in your slurry to allow the starch granules to enlarge to their full capacity.

Gluten also reduces the thickening power of flour. You need twice as much flour as cornstarch to thicken the same amount of liquid, but an equal amount of arrowroot or cornstarch will do the trick.

While you can store cornstarch almost indefinitely on the pantry shelf, in an airtight container, the quality will degrade over time. If your cornstarch is old, you might need more of it to yield the thickening power your recipe requires.

If it's really old, relegate your cornstarch to the laundry room, where it will work wonders on your wrinkled shirts.

Beef stir-fry with bitter melon

Nancy Soohoo was my neighbor in Boston for nearly 30 years, until she passed away a few years ago, but language kept us from getting to know each other for half of that time. It was her small plot in the community garden down the block that brought us together. She’d taken over her godmother’s garden plot, where she grew several varieties of squash, peppers, basil and bitter melon. The melons hung down inside a chicken-wire frame, and when she invited me to view her garden, I felt like I'd entered a cave dripping with stalactites. All the proportions in this recipe, which Nancy gave me with the help of a translator, depend on the size of your bitter melon (they can be as small as a cucumber, or as large as a giant zucchini), so think of it as a method more than a recipe. Salting bitter melon helps to reduce the bitterness, but it’s still an acquired taste. If you haven't acquired it, use a couple of zucchini or seedless English cucumbers instead, and stir-fry them with the meat. Serves 4, as part of a Chinese dinner.


1 small bitter melon
Kosher salt
3 Tbsp peanut oil
1 clove garlic, sliced
1/2 lb flank steak, sliced thin
2 Tbsp black bean sauce (use the Asian sauce made from fermented black beans, not the Mexican variety)
1/2 tsp sugar
2 tsp cornstarch dissolved in 1/3 cup water


Cut the bitter melon in half lengthwise, and scrape out the pits. Mix 1 Tbsp salt with 4 cups of water in a large bowl, and soak the melon (or cucumber) for 5 minutes. Drain, rinse, then sprinkle 1/4 tsp salt directly on the cut side. Place in a pot of boiling water and boil for 5 minutes. Drain, then cut into julienne strips. Heat a wok, and add 1-1/2 Tbsp peanut oil. Add the melon, toss, and add 1/2 cup water. Cook 8-10 minutes, until the melon is tender. Drain and place on a serving plate. Add 1-1/2 Tbsp oil to the wok, and stir fry the garlic for 15 seconds. Add the beef, and continue to stir.  Add black bean sauce and sugar, and stir 1-2 minutes more. Pour in the cornstarch solution, and stir until thickened slightly. Place the meat on top of the bitter melon, and serve hot with steamed rice.

[Printer-friendly recipes.]

More recipes in The Perfect Pantry:

Hot and sour soup
Poppy seed torte
Slow-cooked beef and green chile stew
Asparagus-cashew stir fry
Spice cake

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Oh Lydia, so happy to know you eat bitter melon and cook with it too. You rock! My family loves bitter melon stuffed with ground pork, tofu and just about anything you get get in it. This is a popular Viet dish and it really helps balance out the bitterness.

There are a lot of DBs out there who would love to have know some of this before they started baking the lemon meringue pie!
Pretty scary to think that lemon filling that was so good would starch shirts!!!:))

I never knew that cornstarch turns green as plastic bags, how cool!

Mom cooked bitter melon but I never do, I don't know why. Maybe I should venture and try it myself. Thanks for sharing this recipe. I grew up around neighbours of all ethnic backgrounds. Although we shared food, we never got to share recipes (they seemed quite protective of their treasured recipes...).

Very helpful information on the different thickening agents. Certainly explains why I sometimes get the results I do. Thanks!

Oh Lydia, you brought back bad memories when my brother used to force me to eat bitter melon which we call ampalaya back home. Is till would not eat it. ;). Great info though on the corn starch. Another use of cornstarch is in deep fry especially Asian food. I find the pieces crisper when rolled in cornstarch than flour.

Lots of things I didn't know about corn starch here! In addition to thickening stir fry sauces, I use it to make crêpes. The recipe I use is from Rose Levy Beranbaum and produces extremely delicate crêpes. Unlike crêpes made with flour, the batter doesn't need to rest before being used.

Lydia, you always write the best posts. I learn something new each time. Cornstarch is one of those staples that I always have in the pantry. The box lasts a long time, and it's a crisis if I run out. If you need cornstarch...you really need it!

Hi Lydia, I love the story behind this recipe. I've never tried bitter melon but I'm curious now, to see if I've got the taste buds for it.

In Australia, it's possible to buy corn flour that is not made from corn, weird huh. It apparently refers to an old English word for all grains, they were called corns, so our corn flour is very often made from wheat, a bit of a trap for celiacs.

White on Rice Couple, I'd never had bitter melon until I met Nancy. She was worried that I wouldn't like it, and that somehow I then wouldn't like her. I didn't like my first taste of the melon, but Nancy and I became friends around her garden and around this recipe.

MyKitchen, I was actually thinking about that when I read the lemon meringue pie reports from the Daring Bakers last week!

Nora, my neighborhood in Boston was also quite ethnically mixed, with large populations of Chinese, Lebanese and Puerto Rican people. The community gardens reflect the cooking of those peoples, and I have lots of recipes that were given to me by gardeners over the years.

Kathy, whenever something doesn't thicken for me, I've always tried to add more cornstarch -- which I now know is just the wrong thing to do. Explains some of the results I've been getting, too!

Veron, I'm so sorry to bring up this bad memory for you! But I can really understand it -- bitter melon has a distinctive taste, to say the least. I do use cornstarch as a thickener in my Asian cooking, and for stir-frying, too.

Julie, wow! I will definitely have to look up that crepe recipe. Great for people who are gluten-free.

Sher, if you take the cornstarch out of the box and put it in a glass jar, it will probably last forever. I always have it in my pantry, too, but I go through a lot more arrowroot than cornstarch.

One Food Guy, thanks -- I love that so many things in my pantry, and in my recipe collection, have a good story attached. Please let me know if bitter melon agrees with you.

Neil, I didn't know that some corn flour is made from wheat -- very confusing indeed. Is your cornstarch called cornstarch, or corn flour?

I love the look of bitter melon and can only imagine them on the vine. How nice to make the recipe in honor of your friend, great flavors too!

that question is tricky, but it is a good one!
for me corn starch tastes more neutral than root starch, the latter seems carring some sort of "woodsy" flavor :D

I don't blame Linda for being cautious with serving bitter melon. My (viet) mother warns me not to serve bitter melon as a introductory meal to non-Viet diners because they will think I'm a "bad cook".

This is rather off-topic but I have to say the greatest thing was when Argo recently went to a no-mess cornstarch container. Greatest thing since cornstarch was invented.

In college when I first moved out of Mama's kitchen and into my own, I kept messing up my stir-fries...and finally figured out that I had to use cool water to mix the cornstarch first. I was trying to be "efficient" and instead used hot water - which 'cooked' the cornstarch too fast and I ended up with lumps.

darn my efficient nature!

I bought a small bag of arrowroot last week (It ain't cheap!)to make heidi's silky chocolate pudding. I haven't made it yet but has used a little bit of it to thicken a sauce, and it works so quickly comparing to cornstarch. At least you have this recipe from your friend to remember and celebrate her with us. Thanks for sharing my sweet Lydia!

Probably one of my favorite pantry staples! Corn starch does amazing things :)

Callipygia, for several years Nancy's family maintained her garden plot, but just recently they sold their house and moved away. I hope that, come spring, someone will be back in her garden, planting winter melon vines again.

Gattina, I haven't noticed a pronounced taste with arrowroot, which is the only root starch I keep in the pantry. But next time I use it I will pay special attention and see if I can detect a flavor.

White on Rice Couple, I can understand why your mom would say that! Bitter melon isn't the first thing I'd serve to a guest, either!!

Michelle, welcome to The Perfect Pantry. I haven't seen a no-mess container in my local market -- what a great idea, though. I always decant my cornstarch into a glass jar -- making sure to include a bit of the label from the box, so I can identify which powdery white stuff is in there.

Steamy, yes, cool water for slurries -- thank you, I forgot to mention that. Then when you add the cool slurry to the hot stir-fry (or stew or whatever), it thickens almost instantly. A miracle of science!

Warda, that's the thing about starches. The root starches work more quickly, but also break down more quickly. I have another funny memory of my neighbor. She was quite an elegant woman, always dressed beautifully, but no matter what the weather she wore mules, those high-heeled, open-backed shoes. I remember her walking in the snow, in her mules -- and in the rain, in her mules -- and to her garden, in her mules!

Kristen, now I'll have to check your blog to see what you're making with cornstarch....

Wow- how very informative! I remember when I was a little girl, my mother had a lady who would come to our house to the the ironing...she always had a little pail of white "goo" and now I now what it was! Thank you for sharing and broadening my knowledge in the kitchen.

Who would have thought--corn starch! This was fascinating, I love the behind the scenes stories!

Common usage here is corn flour, both wheat and corn types are available, but you do have to look. Interestingly, corn flour made from wheat is ground much finer than regular wheat flour, mimicking the look of corn starch.

Katia, goo or no goo, it must have been wonderful to have someone come and iron. I remember my mother being particularly bad at it, and I was never that great either!

Cakespy, thanks -- so much of what I know about my pantry, and about food, comes from writing articles about people who know more than I do. It was great to have many Chinese neighbors in Boston, because we had wonderful Asian markets in our community.

Neil, confusing! I'm glad that here in the US, corn flour -- and cornstarch -- are corn.

Also known as Maizena. I even could get 'Maizena Express' in Spain which you can pour right into whatever you want thickened...handy, but expensive!
It took me a long while to figure out the corn flour and cornstarch were the same once I moved.... Don't know why, it's very logical... Sometime the brain just rebels!

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