Kimchi Yeast Film vs Mold: Storage and Disposal Rules

Golmaji on kimchi is a white film produced by yeast. If it is golmaji, the guidance is to skim it off, wash the kimchi, and then cook it. However, a white appearance alone does not confirm that it is golmaji. If mold is suspected or the two are difficult to distinguish, it is safer to discard the kimchi without eating it.

The storage temperature in this article is based on the World Institute of Kimchi's announcement dated November 22, 2018.

What golmaji is and why it forms

Golmaji is a white film that forms as yeast grows on the surface of fermented foods. Lactic acid bacteria drive most of the fermentation in kimchi. In the later stages of fermentation, golmaji may appear as lactic acid bacterial activity declines.

Exposure of the surface to air contributes to golmaji formation on kimchi. It creates conditions in which yeast can grow. Golmaji also appears on other fermented foods, such as soy sauce and soybean paste. This explanation is based on the World Institute of Kimchi's 2018 announcement.

Yeasts and molds are both fungi, but they grow in different forms. Yeasts exist mainly as single cells. Molds on food generally grow as threadlike structures called hyphae. Simply calling golmaji “white mold” can cause confusion about how to handle it.

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Kimchi should be stored at 4°C or below with minimal exposure to air.

Differences between kimchi golmaji and mold, and the limits of visual identification

Color and shape provide clues, but they are not tests that establish safety. Golmaji may appear as white spots or a film. Mold can also look white. Therefore, “if it is white, it is safe to eat” is not a valid rule.

The World Institute of Kimchi advises against eating kimchi with colored, threadlike mold. The USDA explains that some food molds can extend below the surface. Photos or outward appearance alone cannot reveal the condition inside. The sources are the World Institute of Kimchi's information cards and the USDA's guidance on food molds.

What the safety studies established

The findings must be interpreted within the scope of the yeasts tested and the test conditions. The 2018 announcement and the 2022 follow-up study used different assessment methods. Genetic analysis and actual toxicity testing should not be described as the same result.

The 2022 study used cells derived from human intestines and liver, as well as mice. Animal testing included a single dose and repeated oral dosing for 14 days. It was not a clinical trial evaluating long-term consumption in humans. Details are available in the Food Microbiology paper abstract.

These findings support the safety of the main yeasts that form golmaji. However, they are not test results for other contamination in the kimchi at home. They cannot be applied as-is when both golmaji and mold are suspected.

When to remove growth and when to discard kimchi

Before following the removal guidance, there must be no suspicion of spoilage other than golmaji. The table below combines the institute's guidance with general food safety guidelines. Discarding kimchi when the growth is difficult to identify is a conservative decision that accounts for uncertainty.

The USDA advises against removing only the surface mold from soft foods with high moisture content. This guidance does not specifically list kimchi. It is applied here because kimchi is a high-moisture food. Rules for cutting away part of a firm raw vegetable should not be transferred to kimchi.

Handling steps when the growth is identified as golmaji

The guidance for removing golmaji from kimchi follows this order: skim off, wash, and cook. The World Institute of Kimchi's “Identifying Kimchi Golmaji, Often Mistaken for Mold” includes the following sentence.

If golmaji forms on kimchi, skim it off, wash the kimchi in water, and cook it before eating.

1. Use a clean utensil to skim off the part where golmaji has formed.
2. Wash the kimchi you will cook with water.
3. Use it in a cooked dish, such as a stew or stir-fry.

These steps are not a way to salvage moldy kimchi. The quoted guidance does not specify a cooking time or internal temperature. An arbitrary cooking time cannot guarantee safety.

Managing air exposure and storage temperature

The basics of prevention are to reduce the surface's exposure to air and keep the temperature low. The World Institute of Kimchi recommends a storage temperature of at most 4℃. Simply putting kimchi in a refrigerator does not prevent golmaji from forming.

1. Arrange the kimchi so that its surface is submerged in the existing brine.
2. Cover any exposed surface with food-safe plastic film or a similar material.
3. Close the container lid and store it at a low temperature.
4. Check the temperature of the storage area with a refrigerator thermometer.

If there is not enough brine, covering the surface is an option. Adding water at your own discretion is not part of the cited institute guidance. Checking with a thermometer is also recommended in the FDA's food storage guidance.

The difference between when golmaji appears and how long kimchi is safe to eat

The time it takes for golmaji to appear is not the period during which kimchi is safe to eat. The World Institute of Kimchi's information cards dated May 15, 2024, present the following observations. They explain that the timing varies depending on the condition of the ingredients and how thoroughly they are washed.

These figures cannot be applied to every household's kimchi. They should not be read as meaning “it is safe until 3 weeks have passed.” There is also no basis for saying that the storage period starts over on the day golmaji is removed. The guidance does not give a universal number of days for which kimchi can be eaten after removal.

Common mistakes

A common mistake is treating the identity of golmaji and the overall condition of the kimchi as the same issue. The research findings provide evidence about specific yeasts. They are not tests that explain every change that occurs during storage.

• Avoid identifying growth as golmaji based on its white color alone.
• Do not keep kimchi suspected of having mold just because you plan to boil it in a stew.
• A normal smell alone does not establish safety.
• Do not put your nose close to food suspected of having mold to smell it.

The FDA explains that disease-causing microorganisms may be present even when food looks and smells normal. The USDA advises against sniffing moldy food directly. After discarding it, check the storage area and nearby foods for contamination as well.

Key questions in this article

Is every white film golmaji?

White color alone cannot confirm it. Mold can also look white. If the growth cannot be identified, it is safer not to apply the golmaji removal guidance.

Is golmaji a type of lactic acid bacteria?

The microorganisms that produce golmaji are yeasts. They are different from lactic acid bacteria. The microorganisms that drive the main fermentation of kimchi must be distinguished from those that form the white film on its surface.

Does golmaji also change the taste?

Golmaji formation can be associated with declining quality. The institute describes stale odors and softening. Toxicity test results for yeasts do not guarantee taste or texture.

Can I just wash it and eat it raw?

The cited institute guidance includes cooking after washing. Washing alone does not complete the recommended steps. If mold is suspected, these handling steps should not be applied at all.

Can I take out and eat the kimchi beneath the brine separately?

Kimchi in a container suspected of having mold is not safe simply because it is beneath the brine. The visible area and the actual extent of contamination may differ. It is safer to avoid discarding only the outer portion and eating the rest.

Can golmaji form even in a kimchi refrigerator?

It can form even during cold storage. Low temperatures delay its appearance. Surface exposure to air must also be reduced.