Winter is here, and it's time to nourish the body. As a food-medicine homology ingredient, Chinese yam is also a common "health food" for many people in the winter. So, how should you select iron-stem yams and regular yams?
How to Select Iron-Stem Yams
Compared to regular yams, iron-stem yams are "short," "thin," have "long hairs," "have a head and a tail," and have a "delicate cross-section." Iron-stem yams are generally not longer than a ruler and not thicker than two fingers, unlike other yams which are often as thick and round as an arm.
The iron-stem yam has a slender, firm body, and it is said that they don't break easily when tapped with each other (a bit of an exaggeration). Because they are short and thin, they are usually sold whole, unlike other yams which are cut into pieces due to their length.
Iron-stem yams have long hairs, a darker skin color, and sometimes purple spots. They are often larger at one end and smaller at the other, with a thin tail that can sometimes account for half of the length. They are not as uniformly thick as regular yams. The cut surface of an iron-stem yam is delicate, with a porcelain-white color and a firm, dense, and fine texture like jade. Regular yams have a high water content, a loose texture, no porcelain-like luster, and a noticeable granular appearance.
The cross-section of an iron-stem yam does not turn yellow easily. Regular yams turn yellow quickly after being cut if not treated. They are very resistant to cooking and do not become mushy even after prolonged boiling. The texture is delicate, soft, and powdery, sweet and delicious, with a slight medicinal flavor.
How to Select Regular Yams
The type of yam we most commonly eat is the regular yam. Regular yams are relatively inexpensive, can be used in cooking and medicine, and are more accessible to the average household.
When selecting regular yams, choose those with many hairs and that are heavy (this will result in a relatively softer texture). Choose those with less water content (high in dry matter, easy to store), a cross-section that does not turn yellow easily (easy to store), and one with a lot of mucilage after being cut (high in yam polysaccharides and glycoproteins, meaning high nutritional value).
If the cross-section is reddish with a hard core and the juice is not sticky but watery, it has been frozen. It's best not to choose these.