Japan's Long Relationship with Fermentation

Long before anyone spoke of gut health or probiotics, Japan had built an entire culinary tradition around fermentation. From the miso soup that opens a traditional breakfast to the pickles served alongside almost every meal, fermented foods are woven into the fabric of daily Japanese eating in a way that is both practical and deeply cultural.

Understanding these foods — what they are, how they're made, and how they're used — opens up a richer experience of Japanese cuisine, whether you're cooking at home or eating your way through Japan.

The Key Players

Miso (味噌)

Miso is a fermented paste made from soybeans, salt, and a mold called koji (Aspergillus oryzae). The fermentation period can range from a few weeks to several years, and different regions of Japan have their own distinct styles:

  • Shiro miso (white miso): Short fermentation, mild and slightly sweet. Common in Kyoto cuisine.
  • Aka miso (red miso): Long fermentation, robust and salty. Associated with Nagoya and the Chubu region.
  • Awase miso: A blend of white and red, commonly used in everyday cooking across Japan.

Beyond soup, miso is used as a marinade for fish and meat, a glaze for vegetables, and a base for sauces.

Natto (納豆)

Natto is fermented soybeans — sticky, stringy, powerfully aromatic, and beloved or deeply avoided depending on who you ask. Made by fermenting soybeans with Bacillus subtilis, natto is a breakfast staple in many Japanese households, typically eaten over rice with soy sauce and mustard.

Its strong flavour and unusual texture make it a genuine acquired taste, but it is nutritionally impressive and genuinely important to Japanese food culture.

Tsukemono (漬物)

Tsukemono literally means "pickled things" and covers an enormous variety of Japanese pickled vegetables. Methods include:

  • Shiozuke: Salt pickling — the simplest method, used for cucumber, cabbage, and daikon.
  • Nukazuke: Pickling in fermented rice bran. Produces intensely flavoured, probiotic-rich pickles.
  • Amazake-zuke and kasuzuke: Pickling in sake lees or sweet rice wine.

No traditional Japanese meal is truly complete without a small dish of tsukemono on the side.

Shoyu (醤油) — Soy Sauce

Soy sauce is so ubiquitous it is easy to forget it is a fermented product. Traditional shoyu is made by fermenting a mixture of soybeans and wheat with koji mold for anywhere from six months to several years. The result is a deeply complex condiment with hundreds of flavour compounds. Quality varies enormously — a good artisanal shoyu from a traditional brewery is a revelation compared to mass-produced versions.

Mirin and Sake

Both mirin (sweet rice wine) and sake (rice wine) are fermented beverages that serve crucial roles in Japanese cooking — adding depth, sweetness, and complexity to everything from simmered dishes to glazes and marinades.

How to Start Exploring

If you're new to Japanese fermented foods, a practical starting point is miso. Buy two or three different varieties and taste them side by side. Notice how the flavour, colour, and aroma differ. Then try using them in simple ways: dissolved in hot water as a basic soup, as a glaze on roasted vegetables, or stirred into a salad dressing.

Fermentation is at the heart of why Japanese food tastes the way it does. Once you start noticing it, you'll find it everywhere.