What Is Yam? Introduction to Common Varieties on the Market
The scientific name of yam is Chinese yam (Dioscorea polystachya), a twining herbaceous vine of the genus Dioscorea in the family Dioscoreaceae. It grows on hillsides, under forest in valleys, and among shrubs or weeds along streams and roadsides. Its tubers are long and cylindrical, and its stems are usually purplish red. So, what is yam? What common varieties are there on the market?
1. What is yam?
1. Yam is a vegetable. Its tubers are edible, and it is one of the earliest plants eaten by humans. As far back as the Tang Dynasty, the poet sage Du Fu wrote the famous line “filling the stomach with much Chinese yam.” The tubers are thick and juicy, sweet and mealy, and somewhat sticky; they are delicious whether eaten raw or cooked. The tubers contain on average 14.48% crude protein, 3.48% crude fiber, 43.7% starch, 1.14% sugar, 2.62% potassium, 0.2% phosphorus, 0.2% calcium, 0.14% magnesium, and 5.51% ash. Of the 18 amino acids needed by humans, yam contains 16.
2. Yam is a traditional Chinese medicine. The roots are dug in November to December, the root heads are cut off, the soil is washed away, the outer skin is scraped off with a bamboo knife, and the roots are sun-dried or oven-dried to make hairy yam. Hairy yam can be processed into smooth yam, which has the effects of tonifying the spleen and nourishing the stomach, promoting fluid production and benefiting the lungs, and tonifying the kidneys and securing essence. It is used for symptoms such as poor appetite due to spleen deficiency, chronic diarrhea, cough and panting due to lung deficiency, spermatorrhea due to kidney deficiency, leukorrhea, frequent urination, and consumptive fever with thirst.
3. Yam is a widely distributed plant. In China it is distributed in Henan, Anhui, Jiangsu, Zhejiang, Jiangxi, Fujian, Taiwan, China, Hubei, Hunan, Guangdong, Guizhou, northern Yunnan, Sichuan, eastern Gansu, and southern Shaanxi. It grows on hillsides, under forest in valleys, and among shrubs or weeds along streams and roadsides. Its tubers are long and cylindrical, growing vertically, and can reach more than 1 m in length. The cut surface is white when dry, and the color is usually purplish red.
2. What common yam varieties are there on the market?
1. Tiegun yam: It is one of many yam varieties and has rust-like marks on it, hence the name. It is mainly distributed in present-day Wen County and Qinyang (the ancient Huaiqing Prefecture) in Jiaozuo, Henan, and other places. Because of differences in soil, it is divided into two types: loess-soil Tiegun yam and sandy-soil Tiegun yam. The Huai yam produced in the ancient Huaiqing Prefecture has higher medicinal value.
2. Ma yam: It mostly grows in cool mountainous areas. Its tubers are long and cylindrical, growing vertically, and the body can reach more than 1 m in length. The cut surface is white when dry, and the stems are usually purplish red and hairless. It can be used as medicine and is suitable for physical weakness, mental fatigue, loss of appetite, indigestion, chronic diarrhea, consumptive cough, spermatorrhea and night sweats, diabetes, and increased nighttime urination.
3. Lingzhi yam: It is a rare new yam variety used as both food and medicine. The Economic Development Zone of Qingzhou City and Changyi City in Shandong Province are the main growing and distribution areas. Its shape is like a wine pot, wide at the bottom and narrow at the top; some are long club-shaped or short fan-shaped. The outer skin is light yellowish brown, and there are very few fibrous roots. Regular consumption can tonify the spleen and stomach, lower blood pressure and blood sugar, resist tumors, and delay aging. It is suitable for processing into yam paste, yam powder, and other export products.
4. Yamato long yam: It is a high-yield yam variety introduced from Japan. It is planted relatively widely in Pei County, Xuzhou City, Jiangsu Province, China. It can be sown in mid-April each year, with a trench spacing of about 100 cm, a trench depth of 130 cm, and a plant spacing of 25 cm. The density is about 3,000 plants per mu, and it can be harvested about 180 days after planting.