A research team in Yunnan province has identified a locally sourced microbial "repository" that could revolutionize the flavor profile of Chinese Arabica coffee, pushing local beans into the elite "specialty" category through targeted fermentation.

Led by Qiu Minghua at the Kunming Institute of Botany, part of the Chinese Academy of Sciences, the team discovered that endophytic fungi — microorganisms living naturally inside coffee cherries — can act as "natural processing plants" to significantly enhance aroma and sugar content.

The study, recently published in the journal Food Chemistry, successfully isolated 655 fungal strains from five major Yunnan Arabica varieties. One specific strain, Talaromyces funiculosus KQ2, increased sensory scores by 1.5 points, while introducing distinctive vanilla and cinnamon notes. This is a critical technical jump, as it elevates local beans above the 80-point threshold required to be classified as "specialty coffee" by international standards.

"Traditionally, coffee flavor has been shaped by variety, geography, processing and roasting," Qiu said. "In recent years, microbial fermentation has become an important way to improve flavor."

However, conventional fermentation often relies on externally introduced microorganisms such as enzymes and lactic acid bacteria, which can make it difficult to replicate the complex flavor profiles tied to local coffee ecosystems, he said.

Metabolomic analysis also showed a 17.11 percent increase in sucrose content, along with 40 strain-specific metabolic markers, including both water-soluble and volatile compounds. These findings help explain how endophytic fungi influence flavor formation and provide a scientific basis for more precise fermentation techniques.

Qiu likened the fungi to "natural processing plants" within coffee cherries. Compared with introduced strains, they often show stronger enzyme activity and unique metabolic pathways, enabling them to break down complex compounds more efficiently and generate richer flavor precursors.

For Yunnan coffee, this could be especially significant.

"Yunnan coffee has long been relatively weak in floral and fruity notes," Qiu said. "But endophytic fungi contain many aroma-producing microorganisms. By identifying strains with stronger flavor expression, we can enhance these characteristics."

As Yunnan moves from being just a supplier of raw beans to a producer of higher-value specialty coffee, developing distinctive local flavors has become a priority.

The province remains China's leading coffee exporter, accounting for more than 40 percent of the country's total exports in 2025, according to Kunming Customs. Industry output has also surged, growing from less than 10 billion yuan ($1.45 billion) to nearly 100 billion yuan in just three to four years, according to provincial authorities.

Building on Qiu's findings, Wang Xianwen, director of the Technology and Industry Research Center at Baoshan Inspection and Testing Institute, said efforts are now focused on translating the research into industry standards.

"We aim to promote standardized fermentation technologies and establish quality benchmarks for specialty coffee," he said. "This will support the continued development of Yunnan's coffee industry."

Contact the writers at yanyj@chinadaily.com.cn