Where does Chinese yam come from? A complete overview of the latest production areas

The original production area of Chinese yam was Jiaozuo, Henan. It is now also produced in Hunan, Hubei, Shanxi, Yunnan, Hebei, Shaanxi, Jiangsu, Zhejiang, Jiangxi, Guizhou, Sichuan, Shandong and other places. By the Si River in Taiping Town, Shandong, Chinese yam output is not large, but its quality is very high, and it has a relatively long history; it was once a tribute item in the Qing Dynasty.

In Yuting Zan, written by Chen Dasou, a great poet of the Song Dynasty, there is this passage: “In the mountains there is a wondrous herb, green as a fairy prescription; cut several slices of jade, pure white with a floral fragrance”, which refers to a fine winter delicacy——Chinese yam. From Ruichang City, Jiangxi Province, go 20 li west, cross the rolling mountain roads, skirt the picturesque Longyuan Reservoir, and follow the newly built cement country road up the mountain, and you reach Luocheng Mountain, one of the Chinese yam bases of Nanyang Township. The parent soil formed here from weathered limestone after thousands of years of wind and rain erosion provides a special growing soil for Nanyang Chinese yam. The area around Luocheng Mountain in Nanyang has a long history of cultivating Chinese yam. According to the Ruichang County Gazetteer from the Longqing period of the Ming Dynasty, Ruichang Chinese yam has a cultivation history of more than 500 years, and Luocheng Mountain in Nanyang was then one of the important sources of local products and medicinal materials in Ruichang, Jiangxi.

Authentic Chinese yam

① The surface of authentic Chinese yam is yellowish-white or pale yellow, with longitudinal grooves, longitudinal wrinkles and fibrous root marks, and occasionally remnants of light brown outer skin. It is heavy, solid in texture, not easy to break; the fracture surface is white and powdery, with fine dot-like protrusions. The odor is faint, the taste is bland and slightly sour, and it becomes sticky when chewed.

② The starch grains of authentic Chinese yam are simple grains that are flat-ovoid, nearly round, triangular-ovoid or oblong, 8-35μm in diameter; the hilum is dot-like, human-shaped, cross-shaped or short-slit-shaped, and lamellae may be visible; compound grains are rare and composed of 2-3 component grains.

③ The calcium oxalate raphide bundles of authentic Chinese yam exist in mucilage cells, up to about 240μm long, with raphides 2-5μm thick.

④ The vessels of authentic Chinese yam have bordered pits, reticulate, spiral and annular thickening, 12-48μm in diameter.

Adulterants of Chinese yam

① Cassava: often in sliced form, with the outer skin mostly removed; any remaining outer skin is brown or brownish-brown. The cut surface is white and powdery. Near the skin, obvious vein-like ring lines can be seen, and there is a small woody core in the center; some show cracks, and it feels like talcum powder to the touch. The odor is faint and the taste is bland.

② Greater yam: irregular cylindrical or conical, with relatively thick remaining cork, yellow-brown or red-brown; the woody patches are fresh earth-yellow (these are stone cells) and peel off relatively easily. The texture is solid; the fracture surface is pale yellowish-white and powdery, with a few pale brown dot-like substances. It is odorless, sweet in taste and slightly sour, and becomes sticky when chewed.

③ Sweet potato: nearly round or irregular thick slices; the remaining outer skin is relatively thick, pale red or grayish-brown. The cut surface is white or pale yellowish-white, slightly elastic, and pale yellow-brown “vein” dots or line markings can be seen; near the skin, a ring of pale yellow-brown ring lines is visible. The texture is crisp, powdery and sweet in taste.