Common yam, also known as vegetable yam, is characterized by thick skin and no "rust spots". When you pinch it with your hands, you can see that it has more water and is easy to break. Thin skin, brush off, feel greasy. The cut surface is easy to be oxidized, light in weight and easy to rot when cooked for a long time. Compared with vegetable yam, Dioscorea opposita has unique weight, greasy quality, delicious taste, high efficacy and non-perishable cooking characteristics. Generally, it is a slightly long and round cylinder, thin on the top and thick on the bottom, much like a wooden stick, and some are flat and wide in shape, generally 60 cm to 90 cm long.

Two: the difference between ordinary yam and iron yam.

Yam can be subdivided into many varieties, such as iron stick yam, white skin yam, small fluff yam and so on. Iron stick yam is a variety of yam. Iron stick yam belongs to the "best" of Huai yam. Compared with common yam, iron stick yam is even in thickness, usually 1cm ~ 2cm in diameter, slightly hairy, slightly dark in skin color and full of powder and greasy. After crushing, its cross section is white or yellowish, and it will not rot if it is cooked in water for a long time. Because it is rich in a lot of amino acids, the juice is delicious, and the mouth feels "sweet" and has a faint hemp taste.

Three: What is the difference between loam iron bar yam and sandy iron bar yam? Iron stick yam can be divided into two types due to different soil quality: iron stick yam with deep soil layer and iron stick yam with sandy soil. Among them, the iron stick yam in the building is tortuous because of its hard geology, high viscosity and hard soil. Although it is not very beautiful, it is the best of iron stick yam, with good taste and high nutritional value.

Sandy iron stick yam is planted in sandy soil, with soft soil and slightly worse taste than loam iron stick yam. It is cylindrical, usually 60 cm to 80 cm long, the longest is over 65,438+000 cm, and the diameter is about 2.5 cm. The epidermis is earthy brown, densely covered with fine hairs and with purple dark spots. The skin of iron stick yam in Lou soil and sandy soil in Wenxian county is very thin, especially after cooking. Dioscorea opposita is the most authentic yam produced in Guhuaiqing area (now Jiaozuo City, Henan Province), and it is called Dioscorea opposita or Hu Aishan. The "iron stick yam" recommended for everyone, the real "Huai yam" should be called the top yam, so-called iron stick yam! The climate here is summarized by experts as "not too dry in spring, not too hot in summer, not too waterlogged in autumn and not too cold in winter", which is especially suitable for the growth of yam. As the saying goes, "oranges are born in Huainan and oranges are born in Huaibei." Ancient famous doctors such as Sun Simiao, Zhang Zhongjing and Li Shizhen. All used drugs are classified according to the place of origin. Just like Ejiao is authentic in Dong 'e, Shandong Province, ginseng is authentic in Changbai Mountain, and yam is recognized as the origin in Huaiqing, Henan Province.