How to Prep and Store Chinese Yam 'Nagaimo'


What you see on the label at the Farmer's Market:
Kanji: 長芋
Hiragana: ながいも
Katakana: ナガイモ
Seasonal Harvesting Period: Summer-Autumn

The Basics:

Nagaimo is a type of yam in Japan, sometimes called 'yamanoimo' or 'yamaimo' or mountain potato/yam. It is long, cylindrical and resistant to low temperatures. When not grown by human hands, this yam naturally grows as thin as gobo burdock (almost as thin as a finger)! However, nagaimo that are grown in controlled environments are made to be thicker like a regular yam or potato.

Nagaimo is different from other potato varieties, because you can eat it raw! It is also called 'tororoimo' because when you grate it raw it comes out 'toro-toro', or melty/syrupy.

When picking out a nagaimo at the market, check the end for any rot. If you buy a long, whole yam instead of a cut one, choose one with thickness somewhat consistent from end to end. Many believe the more hairs, the better, but this is not necessarily true. Do not judge the yam based on the quantity of hairs sticking out.

Nutritional Info:

Raw: Potassium (430mg)

Other notable components: Glucomannan, Amylase 

Common ailments it is helpful towards: promotion of digestion, helps an upset stomach, myocardial infarction prevention, cerebral infarction prevention, hypertension prevention

The stickiness of nagaimo is due to slimy ingredients such as glucomannan. Glucomannan is said to have the effect of promoting defecation and preventing constipation, and suppressing the absorption of sugars.

It also contains the digestive enzyme amylase, therefore it can be thought to prevent indigestion and an upset stomach. However, amylase is sensitive to heat, so you will need to eat it raw for these effects.

It also contains a large amount of potassium, which helps suppress swelling by diuretic action and suppress a rise in blood pressure by helping rid of excess salt.

How to Wash and Cut:

When eating raw: lightly wash the yam. If the hairs are bothersome, you can burn them off like below using fire (be careful!!) or pick them off as much as possible.

Then feel free to start grating and eat it as is! No further preparation is needed when eating raw, whether you grate, cut, or slice.

When eating cooked: wash the outside of the yam. If the recipe calls for peeling, peel the yam and start cooking as soon as possible since the yam may start to change color. Do not worry though, change in color does not largely affect taste.

When preparing nagaimo, your hands may feel itchy when handling it. This is normal, and if it is bothersome, dip your hands in some vinegar.

Cut the nagaimo like you would any other potato. Chop, slice, or shave. If you do not mind the skin, do not peel it off because it contains many vitamins and minerals!

How To Store:

Wrap the whole yam in newspaper and store it in a cool, dark place, or wrap it in newspaper and put it in a plastic bag and store it in the vegetable compartment of the refrigerator. If you do not have a vegetable compartment, a cool but not too cold area in the fridge is fine. Depending on the condition and environment, it may last for about a month, but the standard is about two weeks. Wrap cut yam in a wrap, store in a refrigerator, and use up within a few days.

You can also freeze grated yam. To prevent discoloration, after peeling, soak in vinegar water and grate. Also, when you put it in a storage bag, it is easier to use it if you press it out flat.

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