Tua Nao: The centuries-old Thai condiment you need to try
Nothing brings Southeast Asian flavors together quite as well as shrimp paste.
Okay, maybe knowledge, skill, and love for cooking, but mainly shrimp paste…
I used to be vegetarian, and of the few things that spoiled plant-based, Southeast Asian recipes — that is, those that normally aren’t — for me, omitting shrimp paste and fish sauce hit the hardest.
There’s nothing quite like taking all the flavor, fat, and umami out of a dish and half-heartedly replacing it with tofu and a squirt of soy sauce, or if you’re lucky to have some, Miso.
But, Miso can be a little sweet and doesn’t always hit the same as shrimp paste (Gapi).
So we look to Thailand…
An old episode of The Splendid Table podcast features Austin Bush — author of The Food of Northern Thailand — nostalgically recounting his travels of northern Thailand and the smell of Tua Nao.
Tua Nao, which roughly translates to “rotten beans” are fermented soybean cakes that have been used as a seasoning in the north of Thailand, and Laos, for hundreds of years.
They’re made from cooked soybeans pounded into a paste and left to ferment for several days. They have a strong flavor similar to shrimp paste and have traditionally been used to add a sense of umami to otherwise simple dishes.
The topic of soybean ferments is not a new one, by any means. Fermented soybeans have been an integral part of Asian cooking for hundreds of years, used as a source of umami and nutrients. There’s no shortage of examples:
Natto and miso in Japan.
Tempeh in Indonesia.
Doenjang in Korea.
Kinema in India and Nepal.
Sieng in Cambodia and Laos.
And Tua Nao in Thailand, among many, many others.
There are two types of Tua Nao:
- Tua Nao Muh (wet) — the cakes are grilled in banana leaves before use.
- Tua Nao Kep (dry) — the cakes are pressed into disks and sun-dried.
Given the short shelf life (a few days) of the wet style and the time required to make it, the dried type is more common and what you should consider making.
Tua Nao has a distinctive, toasty and nutty smell and delivers a big hit of umami in whatever it’s added to — similar to shrimp paste.
While you can also find Tua Nao in northern Laos, it’s said to have originated in the Mae Hong Son province in the far northwest of Thailand — home to the Shan people.
The Shan are an ethnic group related to the Thai, but that doesn’t identify ethnically as Thai.
The north of Thailand is an interesting melting pot of cultures and influences from the neighboring countries of Myanmar (Burma), China (Yunnan), and Laos.
Tua Nao has traditionally been used as a flavor enhancer, long before shrimp paste (Gapi) was prevalent in the north. For many people in the north, meat was scarce while growing up. Some ate it as little as once a year for Buddhist ceremonies or other special occasions, so Tua Nao was used to add bold flavor and umami to otherwise simple dishes.
“In the old days, people would grill those [Tua Nao] and crumble them over rice and I think that was pretty much what a meal was for some people, 80 or 90 years ago” — Austin Bush
These days, Tua Nao is treated much more like a seasoning, and you wouldn’t struggle to find it with chili, salt, and sometimes lemongrass.
Boil, mash, ferment, repeat
Making Tua Nao is simple and the majority of the process — cooking, fermenting, and drying — is passive. Including drying, it takes about a week.
First, soak your soybeans in water overnight. Try to use good quality beans from an Asian market with a steady turnover to avoid excessively dry beans that will take all day to cook.
Cook the beans in a pot of water, or pressure cooker, until tender but not overly cooked to the point that they’re mushy.
You can then decide where to go with it.
You can either ferment the beans (whole) in the same pot with the cooking liquid — sealed well, of course — or strain them, reserving some of the liquid, and mashing them by whatever means necessary — potato masher, blender, food processor; it doesn’t matter.
Use a little bit of the reserved liquid to help get things moving in the blender, if necessary. Be sure to use as little as possible as you don’t want the paste too wet — it’ll make the process of pressing into disks a nightmare.
You can even split the batch and ferment the two differently for some A/B testing.
Ferment your beans, or paste, in a well-sealed (and cleaned) vessel for 3–5 days, until there is a slightly sweet aroma with a noticeable hint of ammonia.
The time will depend on the ambient temperature. The beans will ferment in about three days at 30C — any cooler, you’re looking at five days.
Once fermented, you can either grill or fry and use it immediately in dishes as a seasoning or move on to drying.
As I learned first hand, pressing into disks can be a mammoth task. If you had to add a little liquid to help process your beans into a paste, you’d probably find the paste is too wet to press into disks.
If the disks aren’t happening, spread the paste into a thin, even layer on something that will allow some airflow or that dries with the beans — think banana leaves. A very fine wire cooling rack can work well too.
Drying should take 2–3 days in direct sunlight. Make sure to move it indoors at night.
Once you have some dried disks, lightly toast them in a dry pan or over a low flame and incorporate — by pounding or blending — into dishes that call for shrimp paste.
“If you drive around Mae Hong Son in the morning or the evening, you’ll definitely smell it. It’s still a fundemental part of the cuisine there.” — Austin Bush
The case for bad beans
Few names are as uninviting as “rotten beans,” but given the little effort required and return on flavor, it’s hard to look past Tua Nao.
It’s different from most ferments in that no salt is added before fermenting. It uses bacillus bacteria and not lactobacillus, which most people are more familiar with.
Soybeans give off ammonia as they ferment — hence the name — and while not a pleasant aroma by any means, ammonia isn’t all bad.
All cured or fermented fish products — which have become foundational flavors in Asian cooking — contain ammonia.
So by fermenting soybeans, we’re producing a flavor that hints at the complexity of shrimp paste.
It’s worth noting that many dishes that call for Tua Nao also have shrimp paste, and some would argue that Tua Nao is not a reliable substitute — and maybe they’re right.
But the best judge of that is you.
Regardless, it’s undoubtedly an intriguing substitute for vegetarians or vegans or that can’t get their hands on Gapi. Tua Nao can help bring an umami backbone to meat-free dishes without always relying on miso or soy sauce.
Tua Nao is a compelling exploration for anybody interested in fermentation, those looking to deepen their understanding of Thai flavors, or vegetarians and vegans looking for a reliable alternative to shrimp paste.
The effort is minimal, the reward is plenty, and the options of how you use it are almost limitless. There’s no better time than now than to get behind “rotten beans.”