Historically, Guizhou produced little salt. The province's mountains and poor transport made it hard to obtain. Facing scarcity, early Miao ethnic group settlers in Kaili turned to fermentation, using sourness as a substitute for salt.

For locals, Kaili sour soup as a broth pairs with almost anything — rice noodles, beef, fish, or vegetables. They can hardly imagine life without it. As one local saying goes,"Miss sour for one day and you'll yawn all day. Miss it for two days and you won't want to eat. Miss it for three days and you'll stagger".

Compared with the fiery, oil-rich spicy hotpot that dominates much of the Chinese market, sour soup hotpot is lighter, tangier and more appetizing for some. Its moderate heat makes it widely palatable.

Its influence has even spread as far as the United States. In Silicon Valley, restaurateur Chen Yuzhu runs an eatery that specializes in dishes from his native Guizhou.

Sour soup options have proved the most popular on his menu.

"This is a spicy, sour taste I have never experienced anywhere else," one customer told Chen.

He owns several restaurants in the US, and sour soup remains a signature dish among them.

Guizhou's sour soup has even been integrated with another of the world's great cuisines.

"We supply several restaurants in Milan, Italy. They toss our sour soup with pasta — an unusual but well-received pairing," said Yang Zhengzhou, general manager of Yumeng Group, one of the country's largest sour soup producers.

Yang said the company exports its products to Southeast Asia, Europe and Australia. "We have just set up an international trade department. Overseas sales will move from indirect exports via distributors to direct exports. Our minimum export target is 15 million yuan ($2.12 million) within three years," he added.

Making sour soup is all about the art of fermentation. Traditional methods use earthen jars and local ingredients, with the strict control of temperature, humidity and acidity.

At Yumeng's production base, chilies and tomatoes ferment in large jars. "The jars contain a mother liquor that has been passed down for a long time. After the ingredients are pulped and placed in the jars, they undergo a year of closed fermentation before seeing daylight," said Zhong Dingjiang, vice-general manager of the group.