A worker checks the quality of the fermented soybeans in jars at the Xianshi Jiangyou soy sauce factory, in Luzhou city, Southwest China's Sichuan province, Aug 6, 2015. [Photo by Zhang Ji/For chinadaily.com.cn]

Established in 1893, the company, Xianshi Jiangyou (jiangyou means "soy sauce" in Chinese), has been brewing soy sauce for more than 140 years at its original location along the Chishui River.

Water, salt, wheat and soybeans are the ingredients needed to make soy sauce. Beneficial natural bacteria and old brewing containers make natural yeast for the fermentation process.

The aging process allows the beans to naturally produce oil, resulting in a mellow and full taste and well-balanced aroma, compared with the harsh flavor of non-brewed products. However, natural fermentation takes more than 10 times' longer than the modern chemical process, known as hydrolysis.

The factory has a total of 6,000 jars, and about 2,000 jars of soy sauce can mature each year, producing only 200 to 300 tons yearly, according to Ma Chao, chairman of the factory.