The Science of Japanese Potato Salad (Patreon)

I didn’t grow up eating Japanese-style potato salad constantly, but it showed up often enough that I associate it with the kind of everyday home cooking my mother and grandmother did instinctively, using up potatoes, maybe some ham, and whatever vegetables happened to be around, like peas or cucumber—that is, depending on the day and depending on whose memory you trust.

In fact, before filming this recipe, I texted my mom and sisters to ask exactly what used to go into ours. I distinctly remembered frozen corn. My sisters insisted there was never corn. They remembered onions. One of them claims there was bacon. I don’t remember bacon at all.

It's almost as if three different people have three different experiences and memories. Weird, right?

Japanese potato salad is a living category of food more than a rigid formula. It sits in the same family of dishes like korokke (Japanese croquettes) being practical, adaptable comfort food built around potatoes and odds and ends from the fridge. But despite the flexibility, there are a few things that make Japanese potato salad unmistakably Japanese. It’s the kind of thing you’ll find tucked into bento boxes, sitting next to karaage at a convenience store, or served alongside fried foods at home.

For this version, I'm combining some of the most classic ingredients: boiled potatoes, simmered carrot slices, Kewpie mayo, cucumber, onion, ham, and a boiled egg.

The potatoes are mashed, but only partially, so you get a texture somewhere between mashed potatoes and classic American potato salad. Kewpie mayonnaise adds richness and savoriness. Cucumbers bring cool crunch. Rice vinegar and sugar create a gentle sweet-and-tangy balance. At its best, it's bright, tangy, and light with a wild array of flavors and textures in every bite. And unlike many deli-counter potato salads, the whole thing stays remarkably light and fluffy rather than dense and gluey.

But to get there takes a little care. Texture, moisture management, seasoning, and temperature all matter. As it happens, there are also a whole bunch of little food science and technique lessons boiled into it (...pardon the pun). Let's get into some of them.

Why Russet Potatoes?

Japanese potato salad is supposed to be fluffy.

That texture comes largely from the type of potato you use. Russets are high in starch and relatively low in moisture. As they cook, their cells separate more easily and become dry and fluffy rather than dense. That loose structure allows them to absorb seasoning readily while still mashing into soft, airy chunks.

To demonstrate this, I cut two different potatoes—a russet and a red creamer—into identical chunks, boiled them until tender, then soaked them in a bowl of water tinted with green food coloring. You can immediately see how much more color the russets absorbed. In practice, this leads to easier, more intense seasoning in the finished salad.

Waxy potatoes like Yukon Golds or red potatoes hold their shape better because they contain more moisture and less starch. Their denser, waxier texture works well in many dishes, but for this style of salad, russets create the texture I want: soft, fluffy, and creamy without heaviness.

Why Start Potatoes in Cold Water?

This is one of the most important techniques in the recipe.

Potatoes conduct heat relatively slowly. If you drop them directly into boiling water, the outer layers begin overcooking long before the centers are tender. The starch granules near the surface absorb excess water, swell aggressively, and eventually rupture, leaving the exteriors waterlogged and mushy by the time the middle cooks through.

Starting potatoes in cold water solves this problem. As the water gradually heats, the temperature inside the potatoes rises more evenly from edge to center. The starches gelatinize at a slower, more controlled rate, which means the potatoes cook through before the outsides fall apart.

You end up with potatoes that are more evenly cooked, less waterlogged, better at absorbing seasoning, and easier to mash into fluffy chunks. And given that you have to bring a pot of water (seasoned with salt and a pinch of MSG, please!) to a boil anyway, it actually shaves some time off the process.

Why Salt the Cucumbers?

Cucumbers are delicious. They are also mostly water.

If you slice cucumbers and toss them directly into potato salad, they’ll slowly leak moisture over time. The result is a watery mayonnaise dressing, diluted seasoning, and potatoes that lose their fluffy texture.

Salting the cucumbers solves this with osmosis. When salt is sprinkled onto the cucumber surface, it creates a solute concentration gradient. Water inside the cucumber cells migrates outward to balance the salt concentration, pulling excess moisture out from the vegetable before it ever reaches the salad.

When I salt my cucumbers, I also like to add a small pinch of MSG. Glutamate dissolves readily into that extracted moisture and seasons the cucumbers internally while also amplifying savory flavors throughout the finished salad.

The texture benefits are enormous! The cucumbers stay crisper, the salad stays fluffy instead of wet, and its flavors become more concentrated.

I like using dense, compact Japanese or Persian cucumbers, but English or American cucumbers will also work, so long as you scrape the watery seeds out before salting and draining them. If you want more tips on cutting cucumbers, check out my guide here.

Why Soak Onions in Hot Water?

Raw onion pungency comes from sulfur-containing compounds produced when onion cells rupture. When you cut an onion, enzymes react with sulfur precursors inside the cells to form volatile compounds responsible for that sharp, aggressive bite.

How do you manage this bite? With dilution. Soaking sliced onions in water dilutes and washes away some of those compounds. Most recipes recommend cold water, but hot water works much faster because heat accelerates both diffusion and volatility. The sulfur compounds dissolve and dissipate more readily in warm water than cold.

You might worry that soaking in hot water will essentially cook the onion, softening it before it hits that salad, but never fear! Vegetables maintain their crisp structure because of pectin, a structural carbohydrate that acts like glue between plant cells. Pectin doesn’t begin significantly breaking down until temperatures approach about 183°F (84°C).

Soaking onions in hot tap water—which should, normally, be well below that temperature threshold—lets you mellow their sharpness quickly while preserving crunch and texture, giving you good onion flavor and crunchy texture without the harsh burn.

Why Should I Season my Potatoes While They’re Hot?

This is one of the biggest flavor differences between mediocre potato salad and great potato salad.

Freshly cooked potatoes are full of steam. As they cool, moisture evaporates from their interiors, leaving behind microscopic empty spaces within the starch network.

If you season the potatoes while they’re still steaming hot, those spaces fill with whatever is on the surface, like vinegar, salt, or sugar. The seasoning gets pulled directly into the potato structure itself rather than simply coating the outside. Let me show you a quick picture.

The chunk on the left was cooked in water that was "seasoned" with green food coloring and seasoned with more of it while still hot. The one in the center was cooked in plain water but seasoned with food coloring after it came out. The one on the right was cooked in plain water and seasoned only after it had completely cooled.

As you can see, allowing the potato to cool prevents the seasoning from penetrating as deeply, resulting in a blander salad. (This same principle applied in many starch-heavy dishes: Pasta absorbs sauce more effectively while hot. Rice absorbs seasoning best while steaming. Beans take on flavor most readily while warm.)

Vinegar is especially important here because potatoes readily absorb acid while hot. Waiting until the salad is cold dramatically reduces that absorption.

When flavor is knocking, heat is there to open the door.

The Science of Easy-to-Peel Eggs

People have strong opinions about how to boil eggs, and if there's one thing I've tested more than anything else, it's eggs. Particularly what makes them easily peelable after boiling.

The single biggest factor affecting peelability is whether the egg starts in cold water or already-boiling water.

When eggs heat gradually from cold water, the proteins near the shell bond tightly to the inner membrane before the whites fully set. Those bonds make peeling frustrating because chunks of white tear away with the shell.

Starting eggs in boiling water changes the timing.

The outer egg proteins coagulate rapidly before extensive bonding can occur between the white and the membrane. That faster setting creates a cleaner separation layer and dramatically improves peelability. There’s no absolutely foolproof method because egg age and shell structure still vary, but starting in boiling water consistently improves the odds more than any other single variable I’ve tested.

The one downside is for eggs with more delicate shells, the expansion of the air space near the fat end of the egg from the heat of the boiling water can cause the shell to crack. The easy fix is to poke a push-pin or needle through the fat end of the shell to create a little hole for pressure to escape before lowering the eggs into the hot steamer or boiling water.

Why Do Cold Foods Need More Seasoning?

Temperature dramatically affects flavor perception.

Cold temperatures suppress volatility, meaning fewer aromatic compounds evaporate into the air and reach your nose while eating. Since much of what we perceive as flavor is actually aroma, chilled foods taste duller than warm foods.

Salt perception also decreases at colder temperatures.

That’s why foods served cold—potato salad, pasta salad, gazpacho, even ice cream—generally require more aggressive seasoning than their warm counterparts.

A potato salad that tastes perfectly seasoned while warm will often taste flat after refrigeration. I always like to season my salad twice: once while I'm making it, and then a double check before serving to make sure that the seasoning is still working with the temperature change.

What I love most about Japanese potato salad is that it's humble, adaptable, and personal food. Every family makes it a little differently, every cook has their own little tricks, and every version can still feel correct. (Except for those with raisins. Leave the raisins out, please.)

Recipe: Japanese Potato Salad

Every recipe I publish here is personally tested, tasted, and approved.

What I love about this recipe:

Creamy, fluffy, and light instead of heavy.

Crisp cucumber and onion balance the rich potatoes.

Deep savory flavor from Kewpie mayo and MSG.

Adaptable to whatever vegetables or leftovers you have around.

Yield: Serves 4 to 6Active Time: 30 minutesTotal Time: 45 minutesNotes: Use russet potatoes for the fluffiest texture. Kewpie mayonnaise is preferred, but regular mayonnaise will work in a pinch.

Ingredients

For the potatoes:

2 pounds (900g) russet potatoes, peeled and cut into large chunks

Kosher salt

MSG

Sugar

For the vegetables:

1 English cucumber, seeded and thinly sliced

1/4 medium onion, thinly sliced

1 medium carrot, peeled and thinly sliced

For finishing:

1 large egg

4 ounces (115g) ham slices, cut into short strips

2 tablespoons (30ml) rice vinegar, plus more to taste

1 teaspoon sugar, plus more to taste

1/4 teaspoon MSG, plus more to taste

1 teaspoon Japanese or English mustard powder mixed with 1 teaspoon (5ml) water

6 tablespoons (90g) Kewpie mayonnaise, plus more to taste

Freshly ground black pepper

Method

Place potatoes in a large pot and cover with cold water by about 1 inch. Add a large pinch of salt, a small pinch of MSG, and a tablespoon of sugar. Bring to a boil over high heat, reduce to a simmer, and cook until potatoes are completely tender when pierced with a knife, 10 to 15 minutes.

Meanwhile, place cucumber slices in a bowl and toss with 1 teaspoon salt and a pinch of MSG. Let stand for 10 minutes to draw out excess moisture. Drain well and discard the liquid.

Place sliced onions in a bowl and cover with hot tap water. Let soak for 5 minutes. Drain well and discard the liquid.

When potatoes are tender, use a slotted spoon or spider to transfer them to a rimmed baking sheet or large bowl. Sprinkle immediately with 2 tablespoons (30ml) rice vinegar, 1 teaspoon sugar, salt, and a pinch of MSG while still hot.

Return the potato cooking water to a boil. Add carrot slices and cook until tender but not mushy, 2 to 3 minutes. Remove with a spider or slotted spoon.

Carefully lower egg into the boiling water and cook for 6 minutes for a jammy yolk or 9 to 10 minutes for hard-boiled. Prepare a cup or bowl of cold water and transfer the egg to it once cooked.

Squeeze excess moisture from cucumbers and onions using paper towels or a clean kitchen towel.

Roughly mash the potatoes using a potato masher, pastry cutter, or fork until partially broken down but still chunky.

Add cucumbers, onions, carrots, ham, mustard mixture, and mayonnaise. Peel the egg and crumble it directly into the bowl with your hands or chop roughly before adding.

Fold everything together gently until evenly combined. Taste and adjust seasoning with additional salt, MSG, sugar, vinegar, mayonnaise, mustard, and black pepper as needed.

Serve at room temperature. Alternatively, chill for at least half an hour or up to several days before serving cold.

Variations

One of the best things about Japanese potato salad is that almost every family has their own version. Common additions include:

Frozen peas

Corn

Bacon

Apple

Broccoli

Tuna

Crab sticks

Cooked shrimp