How to Make Kombu Water and How It Differs from Dashi

What is kombu water

Kombu water (kombu-sui) is a simple health drink made by soaking kombu seaweed in water overnight. Umami components slowly dissolve, creating subtly flavored water.

Beyond cooking prep, it's gaining attention as a daily health habit. Easy to make, try adding it to your routine.

Kombu water vs dashi

"Kombu water" and "kombu dashi" seem similar but differ in purpose and method.

Kombu water

• Purpose: Drink directly or use as base flavor in cooking
• Method: Soak kombu in cold water, refrigerate overnight (6-12 hours)
• Temperature: Cold water only (no heating)
• Flavor: Subtle umami, clean mouthfeel
• Concentration: Light (drinkable)

Kombu dashi

• Purpose: Cooking base for miso soup, simmered dishes
• Method: Soak then heat on stove
• Temperature: Heat to 60-80°C (remove kombu before boiling)
• Flavor: Full umami
• Concentration: Rich (cooking strength)

Kombu water is light extraction for drinking; dashi is strong extraction as a cooking foundation.

How to make kombu water

Ingredients

• Kombu: 10g (2-3 pieces, about 5cm square)
• Water: 1 liter
• Sealable container or pitcher

Steps

1. Wipe kombu surface lightly

White powder on kombu is umami (mannitol); don't wash it off. Only wipe gently with a damp cloth if dirty.

2. Cut kombu with scissors

Cut kombu into small strips to release umami faster. 5mm-1cm wide strips work well.

3. Soak in water

Place cut kombu and water in container, seal.

4. Refrigerate overnight

Soak in fridge for 6-12 hours. Set up at night, ready by morning.

5. Remove kombu. Done.

Remove the kombu. Leftover kombu can be used in miso soup or cooked into tsukudani.

Choosing kombu types

Kombu types suited for kombu water.

• Ma-kombu: Elegant, clear umami. Best for kombu water, highly recommended
• Rishiri kombu: Clear broth, slightly salty. For those who prefer clean flavor
• Hidaka kombu: Easy to find, soft. Usable but better for simmered dishes
• Rausu kombu: Rich umami, premium. Strong flavor but may be slightly cloudy

Health benefits

Kombu water contains these nutrients.

• Minerals: Calcium, magnesium, iron, iodine. Dissolve into water during soaking
• Dietary fiber (alginic acid, fucoidan): Kombu's characteristic sliminess, supports gut health
• Glutamic acid: Kombu's umami compound, supports digestive function

How to use

Drinking a glass of kombu water each morning is the simplest approach. The subtle umami makes it more palatable than plain water for many people.

Use as cooking water to add natural umami. Great for miso soup base, rice cooking, simmered dishes, and soups.

Storage and precautions

• Refrigerate and use within 2-3 days
• Leaving kombu in too long increases sliminess and bacteria risk. Remove after extraction
• In HCMC's heat, always make in the refrigerator, don't leave at room temperature
• Kombu is high in iodine; those with thyroid conditions should consult a doctor

Kombu water in HCMC

No special tools or skills needed, just kombu and water. Even busy mornings only need prep the night before. Experience Japanese food culture in your daily life.

Download the Farmi app and find the perfect kombu.

Note: This article and some images were created with the assistance of AI (artificial intelligence) and reviewed by the editorial team before publication.