Sunomono
Vinegar-dressed vegetables with the san-bai-zu ratio — 3 parts vinegar, 1 part soy, 1 part mirin — a Japanese salad built on salt-wilting, acidity balance, and the logic of seasoned vinegar.
Ingredients
- 1 medium Japanese cucumber (about 200 g), or 1/2 English cucumber
- 1 tsp fine sea salt (for salt-wilting)
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- San-bai-zu dressing:
- 3 tbsp rice vinegar (about 45 ml)
- 1 tbsp soy sauce (about 15 ml)
- 1 tbsp mirin (about 15 ml)
- 1 tsp sugar (optional — mirin provides sweetness, sugar adjusts if needed)
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- Optional additions: 10 g dried wakame seaweed (rehydrated), small cooked shrimp, thin-sliced octopus, or thinly shaved daikon
Steps
Slice the cucumber as thinly as possible — ideally 1–2 mm, using a mandoline. Place in a bowl, sprinkle with the teaspoon of salt, and toss to coat. Let stand for 10–15 minutes. The salt draws water out of the cucumber cells through osmosis, wilting the slices and concentrating the flavor slightly. This step is not optional: undrained cucumber will dilute the dressing on contact.
Squeeze the salted cucumber slices firmly in your hands to remove as much liquid as possible. The squeezed cucumber should feel almost dry. This concentrated, slightly salted cucumber is the base of the dish. If using wakame, rehydrate in cold water for 5 minutes, squeeze dry, and cut into bite-size pieces.
Make the san-bai-zu: combine the rice vinegar, soy sauce, and mirin in a small saucepan. Heat gently just to a simmer — the brief heat mellows the vinegar's sharpest edge and evaporates a small amount of the mirin's alcohol, making the dressing rounder and more cohesive. Remove from heat and let cool to room temperature. If using sugar, add it while the dressing is warm. Taste: the ratio produces a tart, savory, lightly sweet dressing; the balance point is where no single element dominates.
Combine the cucumber (and wakame and any other additions) with the cooled dressing just before serving. Toss gently to coat every piece. The dressing should lightly coat the cucumber, not drown it. Serve in a small bowl or dish — sunomono is presented as a small portion, not a large salad. Serve immediately or within 10 minutes; longer and the cucumber releases more water, thinning the dressing.
Tools you'll want
Why this works
Sunomono is a lesson in acidity management and osmotic extraction — two techniques that, once understood, apply across a wide range of preparations.
The salt-wilting step exploits osmosis: the salt concentration outside the cucumber cells is higher than inside, so water moves out through the cell membranes to equalize the concentration. The cucumber slices collapse, releasing 20–30% of their water content into the bowl. This matters for three reasons: (1) the dressing makes contact with a less watery substrate and isn't diluted on contact; (2) the cucumber flavor is slightly more concentrated; (3) the texture is pleasantly softer and more pliable, rather than the crisp crunch of raw cucumber. The squeezing step removes the remaining surface and cellular water, ensuring the cucumber is nearly dry when it meets the dressing.
The san-bai-zu ratio — 三杯酢, literally "three-cup vinegar" — is 3 parts vinegar : 1 part soy : 1 part mirin by volume. It is one of the most fundamental ratios in Japanese cooking, used across a wide range of aemono (dressed dishes), sunomono, and dipping sauces. The math of the ratio is easy to remember and scales linearly: 1 tbsp each of soy and mirin, 3 tbsp rice vinegar — that's the base for one or two servings. For a larger batch, multiply uniformly.
Why this ratio works: rice vinegar is mild (about 4–5% acidity, compared to 5–7% for Western white wine vinegar), which means the 3-part volume of vinegar delivers the right level of acidity without the harshness of a stronger acid. Soy sauce adds salt and umami simultaneously — it is doing double duty that salt and a glutamate separately could not replicate as elegantly. Mirin adds sweetness and, crucially, the mellow caramel-adjacent sweetness from its fermentation sugars (which have a different molecular profile than white sugar), plus a light gloss. The brief heating of the dressing rounds the sharpest volatile acids in the vinegar and integrates the flavors more cohesively than simply combining raw ingredients.
The optional wakame is not just garnish — it adds a marine, slightly oceanic note that complements the acidity and gives the dish more textural contrast. Traditional sunomono almost always includes either wakame or a second ingredient (shrimp, octopus, clam) to add interest beyond cucumber.
Common mistakes
Skipping the salt-wilting. A sunomono made with fresh, un-wilted cucumber releases its water into the dressing within 3 minutes, producing a watery, thin sauce at the bottom of the bowl. The wilt is not optional.
Not squeezing firmly enough. Even after the wilt, cucumber holds water in its cells. Squeeze until no more water comes out.
Using the wrong vinegar. Western white wine vinegar or cider vinegar is 1.5–2x more acidic than rice vinegar. Using them directly will produce an unpleasantly sharp dressing. If you must substitute, dilute by 30–40% with water.
Making the dressing too far in advance. The volatile aromatics in the mirin and soy sauce deteriorate quickly once the dressing is made. Ideally, make it and use it the same day.
Dressing the sunomono too early. Within 10 minutes of dressing, the cucumber releases water again, thinning the sauce. Dress and serve within 5 minutes.
Over-salting the wilt. 1 tsp of salt per medium cucumber is the right amount. More than that and the cucumber tastes salty, not just seasoned.
What to look for
- After salt-wilting: cucumber slices visibly softer and translucent at the edges, a pool of water in the bowl. Osmosis is working.
- After squeezing: compact, nearly dry bundle. Water should not drip when squeezed firmly.
- Dressing: pale golden, fragrant, slightly syrupy. Tart first, with savory and sweet notes following.
- Dressed sunomono: every slice coated, dressing lightly visible but not pooling. The vinegar glistens on the cucumber.
Chef's view
The san-bai-zu ratio is worth committing to memory exactly because it is a ratio, not a fixed recipe. 3:1:1 scales to any quantity — 1 tbsp rice vinegar, 1 tsp each soy and mirin, makes a dressing for a single portion. 6 tbsp vinegar, 2 tbsp each soy and mirin, makes a larger batch for a dinner party. The ratio also accepts small adjustments: more mirin for a sweeter, gentler dressing (good with delicate white fish or clams); slightly less soy for a lighter, more acidic version (good with octopus or bitter vegetables). The base ratio is where you start; the adjustments come from tasting.
The Japanese cucumber (kyuri) is the ideal cucumber for sunomono: thin skin, minimal seeds, and a delicate flavor that doesn't compete with the dressing. English cucumber works well. Standard thick-skinned North American cucumbers have too much seed content and more pronounced green cucumber flavor — peel, halve, and seed them before slicing.
Chef Test Notes
Tested san-bai-zu with and without the brief heating step. The heated version was noticeably rounder and more cohesive — the vinegar's sharp top notes mellowed and the mirin's sweetness integrated more evenly. The raw, unheated version was sharper and more one-dimensional, though still usable. The heating step adds 3 minutes and is worth the effort for a finished, restaurant-quality dressing.
Related glossary terms
- Osmosis — the mechanism by which salt draws water from the cucumber cells during wilting
- Umami — the savory depth contributed by soy sauce in the dressing, doubling as the salt component
- Mirin — the fermented rice condiment that contributes sweetness, gloss, and aromatic depth to the san-bai-zu
- San-bai-zu — the 3:1:1 vinegar:soy:mirin ratio at the foundation of this dressing