How to Make Seaweed garum

Seaweed garum is a marine umami sauce made by fermenting seaweed with koji. It delivers ocean depth without fish, perfect for plant-based cooking.

Category: Pastes & Sauces · Method: Fungal/Mold · Time: 3-12mo · Difficulty: 3/5 · Yield: varies · Temp: 18-22°C

History

Developed by modernist chefs, seaweed garum applies ancient garum techniques to marine vegetables, creating intensely umami vegan condiments.

Ingredients

  • 1 lb Dried seaweed mix — Kelp, dulse, nori
  • 1/2 lb Koji rice — Fresh or dried
  • 10% Salt — By total weight
  • To cover Water — Filtered

Equipment

  • Blender
  • Fermentation vessel
  • Cheesecloth
  • Bottles

Instructions

  1. Rehydrate seaweed

    Soak dried seaweed until soft.

    Time: 30 min

  2. Blend

    Process seaweed with water into paste.

    Time: 10 min

  3. Mix with koji

    Combine seaweed paste, koji, and salt.

    Time: 10 min

  4. Ferment

    Ferment 3-12 months at room temperature.

    Time: 3-12 months

  5. Strain

    Filter and bottle the liquid.

    Time: 1 hour

Fermentation Timeline

  • Month 1-2: Start — Koji breaks down seaweed.
  • Month 3-6: Development — Marine umami intensifies.
  • Month 6-12: Mature — Complex ocean flavor.

Signs of Success & Spoilage

Good signs

  • Dark green-brown liquid
  • Ocean aroma
  • Clean umami taste
  • No mold

Warning signs

  • Putrid smell
  • Mold
  • Off flavors
  • Sliminess

Troubleshooting

Weak flavor
Cause: Insufficient koji Solution: Increase koji ratio, extend fermentation.

Storage

Refrigerate Keeps 2 years. A little goes a long way.

Health Benefits

  • Iodine
  • Minerals
  • Antioxidants
  • Glutamates
  • Fiber

Serving Suggestions

  • Vegan fish sauce substitute
  • Ramen broth
  • Grain bowls
  • Vegetable finishing
  • Sushi rice seasoning

Related Pastes & Sauces Ferments

Other Fungal/Mold Ferments

Popular Fermented Foods

More Pastes & Sauces ferments · Fungal/Mold fermentation

Authoritative food-safety sources

This site cross-references but does not replace professional guidance. For canonical, peer-reviewed fermentation safety information, consult:

Report an issue with this recipe →