June 2nd, 2021
Kombu is one of the most, if not the most, commonly used seaweed in Chinese and Japanese home cooking. Apart from being a great source of iodine and many other nutrients, its beautiful texture, intense umami taste and ease of store and use make it a very popular choice for soups and salads.
Instead of turning this post into an introduction of health benefits of Kombu (let’s not even get started on how little we actually know about sea vegetables), I will address a few common questions (which I once had myself) when buying and using a pack of dried Kombu sheets. Hopefully this post will help you enjoy more of this wonderful vegetable the ocean offers to us.
Where to buy: You can buy dried kombu from most Chinese and Japanese stores, in the dried foods section. Dried Kombu kelp are greenish brown in color, and sold in packets of flat sheets.
What to Look for: Choose a good quality and minimally processed kombu kelp, i.e. healthy Kombu kelp harvested from clean water, rinsed off the sand then dried and packaged, and no more. Look for these signs for good quality Kombu sheets:
- free of dirt, debris, scars and excessive amount of sand (a tiny bit is OK).
- smooth surface (without spots and bumps) except crinkles from drying
- have random streaks of white powdery deposits (more on this later)
Sometimes it can be hard to identify a bad pack before opening it, and I do occasionally get disappointed. The good news is Kombu sheets are not expensive so we can afford to try another brand. Stick to a good one once you’ve found it.
How to Use It: Rehydrate the Kombu sheets in water for about 5 to 30 minutes until they are soft, depending on the thickness of the sheets. Thinly sliced Kombu kelp tastes lovely in cucumber or carrot salads; if you are using them in soups, rehydrate for a few minutes (so you can cut them into desirable sizes), then complete the rehydration in soup liquid during cooking.
(Last but not least) What are the white deposits and the slime: First of all, they are nothing to worry about! The white deposit on dried Kombu sheets is mannitol which gives Kombu kelp its umami flavor. When Kombu sheets are in contact with water, the mannitol forms the slime. Since Kombu’s umami flavor largely relies on the presence of mannitol deposit, gentle rinse instead of excessive washing is recommended (and which is why it is important to buy good quality clean Kombu sheets to eliminate the need to wash them).