I’ve written about miso, koji, and natto individually on this blog, but honestly, that’s really just the beginning. Japan ferments an almost absurd range of things — grains, fish, vegetables, tea leaves — and once you start looking, you realize fermentation isn’t a niche category of Japanese food. It’s basically the backbone of the whole cuisine. Nearly every region has its own local specialty too, shaped by climate, water, and generations of trial and error long before anyone understood the microbiology behind it. So here’s the wider tour: what’s actually fermenting in a traditional Japanese kitchen, organized by category.
1. Soy and Grain Ferments (The Ones You Probably Already Know)
This is the group I’ve covered before, so I’ll keep it brief:
- Miso — fermented soybean paste, the backbone of miso soup
- Shoyu (soy sauce) — brewed from soybeans, wheat, and koji, often aged over a year
- Natto — fermented whole soybeans, famously polarizing, famously nutritious
- Koji itself, the mold behind basically everything on this list that involves rice or soy
2. Rice-Based Ferments
- Sake — rice fermented with koji and yeast into Japan’s most famous alcoholic beverage. Different rice polishing ratios and koji strains produce wildly different styles, from dry and crisp to rich and fruity. If you drink, having sake at a proper Japanese izakaya is honestly one of the real joys of visiting Japan.
- Mirin — a sweet, low-alcohol rice wine used constantly in Japanese cooking for glaze and balance. True hon-mirin is genuinely fermented and aged; a lot of what’s sold as “mirin” outside Japan is actually a syrupy imitation with none of the fermentation.
- Rice vinegar — made by further fermenting rice-based alcohol with acetic acid bacteria. This is the vinegar behind sushi rice, and it’s noticeably milder and rounder than Western vinegars.
- Amazake — a sweet, low-alcohol (or sometimes alcohol-free) drink made from fermented rice and koji. Traditionally sold as a warm winter drink, though it’s also become popular as a natural sweetener and smoothie base.
3. Vegetable Ferments
- Nukazuke — vegetables pickled in a bed of fermented rice bran (nuka), maintained daily like a living starter. This is the deep end of Japanese pickling — the bran bed itself develops its own personality over years, sometimes decades, of daily care.
- Takuan — fermented, dried daikon radish, bright yellow and distinctively crunchy. A staple pickle you’ll find at almost any Japanese meal.
- Shibazuke — a Kyoto specialty, eggplant and cucumber fermented with red shiso leaves, giving it a deep purple-red color and tart flavor.
4. Fish and Seafood Ferments
- Katsuobushi — dried, fermented, and smoked skipjack tuna, shaved into flakes. It’s the single most representative ingredient used to make dashi stock. The fermentation step (involving a specific mold, similar in spirit to koji) is what gives katsuobushi its intensely savory depth, and it’s honestly one of the more labor-intensive fermented foods in the world — some traditional versions are aged for months.
- Shiokara — fermented, salted seafood (often squid), intensely briny and an acquired taste even within Japan. It’s usually eaten in small amounts, more like a condiment than a main dish, often alongside sake.
- Narezushi — the ancient ancestor of modern sushi, made by fermenting fish with rice for months. This is where “sushi” actually started, long before anyone was eating raw fish on vinegared rice.
5. Tea Ferments (The Ones Almost Nobody Outside Japan Knows About)
This is the category that surprises people most. A small number of Japanese regions make genuinely fermented teas, as opposed to the oxidized (but not truly fermented) black teas most people know:
- Awa-bancha — a post-fermented tea from Tokushima, fermented with lactic acid bacteria in a process closer to making pickles than brewing tea
- Goishicha — an extremely rare, twice-fermented tea from Kochi, pressed into blocks that resemble go stones (hence the name)
These are genuinely niche even within Japan, but they’re a good reminder of how deep the fermentation instinct runs here — it’s not limited to food in the narrow sense at all.
Why This Matters
Once you see the full list, a pattern emerges: fermentation in Japan isn’t a wellness trend or a specialty category, it’s just how food has traditionally been preserved, flavored, and made more nutritious across nearly every food group — grains, vegetables, fish, even tea. That’s part of why I keep coming back to this topic. It’s not one ingredient to add to your diet; it’s an entire approach to food that happens to also be really good for your gut.
If any of these are new to you, I’d start with something approachable like sake or rice vinegar before working your way toward nukazuke or narezushi — the deep end is genuinely deep. And if you’re shopping outside Japan, sake and rice vinegar are usually the easiest to actually track down, while things like awa-bancha or goishicha may take some hunting through specialty importers.
日本語要約
味噌・麹・納豆以外にも、日本には非常に幅広い発酵食品・発酵飲料が存在します。米由来では日本酒・みりん・米酢・甘酒、野菜では糠漬け・たくあん・柴漬け、魚介では鰹節・塩辛・熟れ寿司(なれずし)、さらには阿波晩茶や碁石茶といった珍しい発酵茶まであります。これらを俯瞰すると、発酵は日本食において一部の健康食品というより、穀物・野菜・魚介・お茶まで含めた食文化全体を支える基本の技術であることが分かります。初めての方は日本酒や米酢のような入りやすいものから試すのがおすすめです。
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