Tuna Pasta with Soy Sauce Koji Recipe

This Tuna Pasta with Soy Sauce Koji recipe is a simple yet flavor-packed recipe that blends the richness of Italian pasta with the deep umami of Japanese koji fermentation.

Instead of relying solely on olive oil or cream, this dish uses soy sauce koji, which is a fermented seasoning made from soy sauce and koji mold, to create a savory depth that pairs beautifully with tuna and mushrooms. The result is a pasta that feels both familiar and entirely new.

Why Soy Sauce Koji?

Koji has been used in Japan for centuries to ferment foods like miso, sake, and soy sauce. When soy sauce is further fermented with koji, it becomes even richer, slightly sweet, and incredibly umami-forward. Adding it to pasta creates a silky, flavorful sauce without the need for heavy cream.

Tuna Pasta with Soy Sauce Koji recipe (2 servings)

Ingredients

• 8 oz spaghetti

• 1 Tbsp olive oil

• 5 oz canned tuna

• 3 Tbsp soy sauce koji

• 1 clove garlic, chopped

• 1 pinch dry chili pepper

• 1/2 bunch shimeji mushrooms

• 1/4 onion, thinly sliced

• 1/4 cup Parmesan cheese (optional, shredded)

Instructions

1. Cook pasta in salted boiling water until al dente. Reserve 1/2 cup pasta water, then drain.

2. Heat olive oil in a skillet over medium heat. Add garlic and chili pepper, cooking until fragrant (2–3 minutes).

3. Add onion and shimeji mushrooms, sautéing for another 2–3 minutes.

4. Stir in tuna and soy sauce koji. Add the pasta (and Parmesan if using), tossing well. Adjust with pasta water if needed.

5. Top with Parmesan and serve hot.

Serving Ideas & Variations

• Spicy upgrade: Add a dash of shichimi togarashi (Japanese chili mix).

• Protein boost: Use fresh seared tuna instead of canned for a more elevated version.

• Vegetarian option: Swap tuna for sautéed zucchini or eggplant.

Dietary Notes

• Gluten-Free: Use gluten-free pasta and ensure soy sauce koji is gluten-free.

• Dairy-Free: Skip Parmesan cheese.

• Not Vegan: Contains tuna, but can be adapted with plant-based protein.