Sourcing & Selecting
When Kimchi is used as a cooking ingredient, over-fermented (sour) kimchi is best. To make Kimchi sour, Kimchi should be kept at room temperature for about a week. Once it's reached a desired sourness, keep in in the fridge.
For fermentation and storage for regular use, see below.
How long should I ferment kimchi for?
Fermentation time depends on temperature and the amount of salt in the kimchi. Lower temperature and a smaller amount of salt will make the fermentation process slower. They say slowly fermenting kimchi in 4-5℃ results in the most tasty kimchi.
The duration of fermentation also depends on your personal preference. Some people like fresh (almost unfermented) kimchi. Some like it very fermented and sour.
I personally like my kimchi fermented to medium sourness. I leave it out in room temperature for 2-3 days. The best way is to leave it out and taste it every day. When it reaches your preference, put it in the refrigerator. If you made a large amount, you can leave some out and store the rest in the fridge right away. Then, take some out later for more fermentation as needed.
Remember that kimchi will produce gas and liquid as it is fermented. Leave some room in the container. Otherwise, it will overflow.
How should I store my kimchi and how long does it last?
Traditionally kimchi is stored in an earthenware called "Ong-gi." Ong-gi (Onggi) is breathable pottery that keeps kimchi and other fermented foods in an optimal condition. In the old days, Koreans used to make kimchi in the fall, then place it in an ong-gi and bury the ong-gi underground to keep the kimchi throughout the winter.
Today, most Koreans use plastic or stainless containers to store Kimchi and keep the containers in a specialized Kimchi fridge. Kimchi fridge keeps kimchi at optimal temperature and keeps your regular fridge free of the potent kimchi smell.
If you don't have any of the above, place the kimchi in a tightly sealed container and keep in the fridge. See below to learn how to prevent kimchi from getting moldy. Kimchi can last 6 months or longer in the fridge but it may get sour in taste. Sour kimchi is perfect for making kimchi stew, kimchi pancakes, kimchi fried rice etc.
I got white mold on my kimchi. Is that normal? What should I do?
Getting molds on kimchi is not ideal. This can happen when kimchi is directly exposed to air as it's fermented. When you place kimchi in a container, make sure you press down firmly to get rid of any air between kimchi. (Do this every time you take out kimchi from a container that contains a large amount of kimchi.) Then, cover the top with a plastic sheet or saran wrap before closing the lid. Finally, make sure the lid is on properly.
Another reason for mold to appear is that you don't have enough salt or enough kimchi sauce/seasoning for the cabbages. During the fermentation, liquid is produced and cabbages get submerged in the liquid. Not having enough seasoning may produce too little liquid. Some people like to pour some water in the container before fermenting.
They say white mold is not harmful. So if it's only on the very top, you can get rid of the top layer and save the rest of the Kimchi. But if you don't want to take a risk, you may want to use the rest for cooking stew, soup or fried rice. If you get different colored (green or black) mold, it's definitely bad for you.
Read more about Kimchi here.