Shio kombu (塩昆布) is one of the great Japanese pantry secrets — thin dark strips of glossy, salty, umami-packed kelp that lift almost anything they touch. A pinch turns a bowl of rice into a meal, makes a cucumber salad taste like an izakaya pickle, and gives pasta a mysterious depth that people cannot place.

Most Japanese homes buy shio kombu in a bag. But if you cook Japanese food, you already throw away the raw material every time you make dashi. This recipe turns the “spent” kombu from a dashi packet or a piece of soaking kombu into a jar of homemade shio kombu — genuinely better than most store-bought.

Finished homemade shio kombu — dark dried strips of kelp coated in a fine dusting of white finishing salt and sugar — piled in a clear freezer bag on a kitchen counter

Why You’ll Love This Recipe

Zero-waste cooking. Uses the leftover kombu from making dashi — a piece you would otherwise throw out.
Better than the store version. Fresher, more aromatic, and you control the salt and sugar.
Endlessly useful. Sprinkle over rice, mix into onigiri, toss with cucumber, add to pasta or salad.
Keeps for weeks. A properly dried batch stores for a month in a sealed bag.

What is Shio Kombu?

Shio (塩) means salt. Kombu (昆布) is dried kelp — the same seaweed that gives Japanese dashi its clean umami. Shio kombu is thin strips of kombu simmered down in a sweet-soy-mirin glaze until the liquid is gone, then dried and finished with a coating of salt.

It sits between a condiment and an ingredient. In Japan, small resealable bags of it are next to the furikake in every supermarket. It ends up on top of a bowl of white rice, tucked into a rice ball, tossed with sliced cucumber for an instant pickle, or stirred through spaghetti with butter.

Save Your Dashi Kombu

Every time you make dashi — whether from a dashi packet that contains kombu, or from a plain sheet you soaked in water for miso soup — the kombu comes out swollen, soft, and full of flavour still. Most recipes tell you to compost it. Don’t. Squeeze it dry, wrap it in cling film, and freeze it. When you have collected around 50 g, defrost and make a batch of shio kombu.

Slice the softened kombu into thin strips — about 3 mm wide and 3 cm long — with a sharp knife. It should look like fine ribbons.

Leftover kombu from making Japanese dashi, sliced into thin dark green strips and piled in a white plastic container — the starting point for homemade shio kombu

Ingredients

Ingredient	Amount	Notes
Leftover dashi kombu	50 g	Sliced into thin 3 mm strips
Sugar	1 tbsp
Mirin	1 tbsp
Rice vinegar	½ tbsp	Brightens the finished flavour
Soy sauce	1 tbsp
Water	150 ml
Unrefined cane sugar	1 tsp	For the finishing coat
Finishing salt	⅓ tsp	A flaky or textured salt works best

Shio kombu starts from leftover dashi kombu (dried kelp), glazed with Japanese soy sauce and mirin. If you can’t find them locally, they’re easy to get on Amazon.

The seasonings for shio kombu lined up on a kitchen counter — a bottle of Takara honmirin, Mizkan rice vinegar, Fundokin Golden Murasaki soy sauce, and a sugar canister — next to a pot with sliced kombu

How to Make Shio Kombu

Step 1: Simmer

Combine the sugar, mirin, rice vinegar, soy sauce, and water in a small saucepan. Add the sliced kombu and stir to submerge.

Thin strips of kombu simmering in a stainless steel pot with a dark sweet-soy-mirin liquid on an IH cooktop — the second stage of making Japanese shio kombu

Bring to a gentle boil over medium heat, then reduce to a low simmer. Stir every few minutes and let the liquid reduce completely — you want the kombu glossy and coated but no pooled sauce left in the pot. This takes about 30–40 minutes depending on your heat. Take it off the heat and let it cool in the pot.

Step 2: Dry in a Low Oven

Line a baking sheet with parchment paper and spread the cooled kombu strips in a single loose layer. Do not pile them — the pieces need air around them to dry properly.

Sticky sweet-soy simmered kombu strips spread in a single loose layer on parchment paper on a black baking sheet, ready to go into a low oven to dry

Place the tray in a cold oven, then set the temperature to 100°C (212°F). Do not preheat — starting from cold gives the kombu a longer, gentler dry. Bake for 25–30 minutes.

How long you dry decides the texture:

25 minutes — pliable, chewy, glossy. Best for onigiri and topping rice.
30 minutes — mostly dry but still slightly bendy. My personal favourite — versatile for everything.
35–40 minutes — fully crisp, snappable. Great for crumbling over salads and pasta.

Take the tray out and let the kombu cool completely on the parchment — it will continue to firm up as it cools. Break any pieces stuck together with your fingers.

Fully dried dark shio kombu strips resting on brown parchment paper after coming out of the oven — glossy, crisp, and ready to be tossed with finishing salt

Step 3: Coat with Finishing Salt

The finish is what makes homemade shio kombu better than store-bought. Choose a good salt with texture — I used Rokusuke shio, a Japanese arajio blended with a touch of scallop stock powder for extra umami, but any flaky sea salt or Maldon works.

A silver pouch of Japanese Rokusuke shio finishing salt held next to a sugar canister and empty freezer bags on the kitchen counter — the seasoning that gives homemade shio kombu its signature clinging umami finish

Drop the cooled kombu into a resealable bag along with 1 teaspoon unrefined cane sugar and ⅓ teaspoon of your finishing salt. Seal the bag with a bit of air trapped inside, then shake and rub gently so every strip is dusted with the salt-sugar mixture. Store the bag sealed.

The finished homemade shio kombu — dark strips of kelp coated in a fine white dusting of sugar and salt — resting in a sealed freezer bag, ready to store for weeks

How to Use Shio Kombu

A little goes a long way. Here are the ways I actually use it week to week:

Over rice. A small pinch on a bowl of hot white rice — nothing else needed.
Onigiri filling. Mix a tablespoon through freshly cooked rice before shaping. Or use it in place of the tuna in classic onigiri-style rice balls.
Instant cucumber pickle. Toss with sliced Japanese cucumber and a splash of sesame oil. Ready in 5 minutes — a cousin of tataki ume kyuri.
Butter shio kombu pasta. Toss hot spaghetti with butter, black pepper, and a handful of crumbled shio kombu. Weeknight magic.
Salad topper. Crumble the crispier version over green salad or sliced tomato in place of croutons.
In soup. A pinch dropped into hot broth adds instant umami — try it in miso soup instead of adding extra salt.

Storing

Store the sealed bag at room temperature away from direct sunlight — it will keep for about 4 weeks if properly dried. For longer storage, keep it in the fridge (up to 2 months) or freezer (up to 3 months). If it ever tastes slightly stale, spread it on parchment and give it another 5 minutes in a 100°C oven to refresh.