Soybeans have been an integral part of Asian cooking since ancient times. The Chinese refined and disseminated the secrets of soybeans fermentation into savory food flavoring agents. From the Natto in Japan to the Indonesian Tempeh, Soybeans are in the roots of Asian cuisine.
In the northern parts of Thailand, the home of the gentle Lanna cuisine, we can find yet another type of fermented soybeans product called Tua Nao.
Tua Nao originated from the ”Tai Yai” (ไทยใหญ่ Shan people) and “Tai Leuu” (ไทยลื้อ) minorities, who inhabits the Burmese and Thai territories of the north-western part of the Kingdom.
In the Tai Leuu dialect Tua Nao refers to Tua Oh (ถั่วโอ่) which simply translate to as bad odor beans.
Two main types of Tua Nao exist:
- Wet (ถั่วเน่าเมอะ ; tua nao muh) (ถั่วเน่าเปอะ ; tua nao bpuh)
- Dry (ถั่วเน่าแข๊บ ; tua nao khaaep).
Making both types of Tua Nao starts with the boiling of soybeans in brine for 4-6 hours. The soft beans are than pounded smooth in a wooden mortar and pastel and let to ferment for 2-3 days.
At this stage, the paste is sometimes lightly seasoned with salt and chilies. The paste is than hand formed into flat cakes.
To make the wet type, the flat cakes are wrapped in banana leaves and grilled over open fire, whereas for the dry variety the cakes are left to dry in the sun.
Before using Tua Nao in food preparations the cakes are lightly grilled and pounded to a fine powder.