For many hotpot lovers, the iconic Chinese dish stirs up thoughts of a deep numbing spiciness. But for many in Southwest China's Guizhou province, hotpot is all about mouth-twisting sourness.

Sour soup hotpot has been gently gathering steam over the past few years, with knowledge and experience of the tangy broth spreading out from Guizhou helped in part by social media.

Look up the hashtag "Guizhou sour soup" on short-video platform Douyin, China's TikTok, and you'll find posts with over 300 million views. People share footage of Guizhou sour soup hotpot enjoyed around the country, and post homemade recipes after visiting Guizhou because they still crave the taste.

As of Dec 1, sour soup hotpot bases from Guizhou topped e-commerce platform Tmall's lists for both positive reviews and repurchase rates. This beloved flavor originates in Kaili, in the Qiandongnan Miao and Dong autonomous prefecture, one of the dish's most famous birthplaces. There, restaurants and street stalls serving sour soup are ubiquitous, and the air often carries the sour scent of fermentation.

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.

The site houses more than 30,000 fermentation jars with an annual capacity of 100,000 metric tons. It supplies authentic Guizhou flavors to consumers in Beijing, Shanghai and beyond, and partners with national restaurant chains including Haidilao and Yangguofu — both of which have introduced sour soup products in recent years, a move that has proven popular among consumers.

Last year, Yumeng Group recorded a total output value of 413 million yuan and produced more than 27,800 tons of sour food products.

Yang credits a turning point to 2023, when the province's Village Super League soccer tournament went viral on social media. "Since then, Guizhou has become a popular tourist destination. Sour soup has become better known and loved, and demand for our products surged," he said.

According to Qiandongnan's sour soup task force office, from January to October, the Kaili sour soup industry chain generated 6.27 billion yuan in output value, up 196.87 percent year-on-year. The region has also expanded main and auxiliary sour-soup crop planting to 32,533 hectares.

"We support enterprises working with research institutions to tackle key technologies such as microbiome regulation, flavor standardization, preservation and intelligent production," said Pan Ningxian from the task force.

Yang said he is optimistic about sour soup's potential in the health-food market, pointing to a recently launched additive-free version.

"Compared with traditional hotpot and many Chinese dishes, sour soup hotpot uses less oil and sugar, which fits young people's expectations for healthier food. Our future research and development will follow that direction," Pan said.