Where the seafood hides
The Codex draft standard for kimchi, reported in 1997, names three basic ingredients: Chinese cabbage, a seasoning mixture of red pepper powder, garlic, ginger, other edible alliums and radish, and salt. None of them is an animal product.
A 2024 Korea.net column by the president of the World Institute of Kimchi lists salted seafood among the secondary ingredients, next to red pepper powder, garlic and ginger.
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Mixing and fermenting its main ingredients like kimchi cabbage, radish and cucumber along with secondary ingredients like red pepper powder, garlic, ginger and salted seafood yields a unique flavor and depth
What jeotgal does to kimchi
Jeotgal is the Korean word for that seafood. Lee and colleagues (2021), researchers at the World Institute of Kimchi, define it in one sentence:
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Jeotgal (salted seafood) is a fermented food obtained by degradation of protein peptides by its enzymes and external microorganisms, imparting a unique flavor and taste to kimchi, while spoilage is prevented by adding large amounts of salt
They also say jeotgal plays an important part in kimchi's savoury taste, and that the same ingredient is behind its fishy smell and high salt content.
Zabat and colleagues (2018) are blunter, in a paper on the kimchi microbiome:
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traditional Korean kimchi is made with jeotgal, or fermented seafood, often in the form of fish sauce
Is seafood required?
Not according to the draft. Salted and fermented seafood is one of eight other permitted ingredients, next to fruit, nuts, sesame seeds and sugars, so the draft treats it as optional.
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(f) salted and fermented seafood;
A 2021 Korea.net column by the British journalist Tim Alper describes anchovy extract or fermented prawn paste as something that can be added to the red marinade for richness.
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For extra richness, anchovy extract or fermented prawn paste (or both) can be added, though vegan-style preparation is increasingly popular.
Kimchi without seafood
Kimchi without seafood turns up in three places: Buddhist temple cooking, some commercial producers, and laboratory trials of stand-ins for jeotgal.
In 2019 Korea.net reported a kimchi tasting in London, where visitors could compare vegetarian cabbage kimchi with the regular kind, which is made with salted fish. The same report describes Buddhist temple food as free of meat and of strong spices such as garlic or green onions.
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Visitors were offered a range of kimchi types to sample, and could even compare vegetarian cabbage kimchi with that made with regular cabbage and salted fish.
Ha Jae-ho, general director of the World Institute of Kimchi, put it this way:
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In particular, temple kimchi is enjoyed by Buddhist monks, who stick to a strict vegetarian diet for practicing asceticism
Zabat and colleagues report that some industrial producers have begun to make kimchi by vegan methods that leave out fermented seafood:
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Recently some industrial producers have begun to utilize vegan production methods that omit fermented seafood ingredients.
They also describe American artisanal makers swapping jeotgal for miso paste:
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To accommodate this segment of consumers, American artisanal kimchi producers are swapping jeotgal for miso paste.
On miso, the paper is clear:
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Miso paste, made by fermenting soybeans and grains, offers a depth of flavor comparable to jeotgal but contains no animal products.
The authors split one mixture into a vegan batch, made with miso, and a non-vegan batch, made with fish sauce. Their bacteria stayed close through fermentation:
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Our results indicate that the bacterial community of the prepared vegan product closely mirrors the progression and final structure of the non-vegan final product.
Lee and colleagues (2021) took a different route. They tested stand-ins for jeotgal, including a tomato extract and a dry-aged beef extract. The beef version is out for a vegan reader. The authors' conclusion covers the tomato-only version, which they call JA1:
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Overall, this study showed that JA1 derived from TH2 could improve the taste and quality of kimchi by increasing glutamic acid content and decreasing the unpleasant flavor.
How to tell from the label
Look for jeotgal, salted seafood, fish sauce, anchovy extract and fermented prawn paste. Any of them in the ingredient list means the jar is not vegan.
Miso paste in their place is the swap the 2018 paper tested. In that study, miso and fish sauce were the only ingredients that differed between the vegan and non-vegan batches, so the ingredient list is where the two versions part.
The paper's statement that miso contains no animal products is the authors' own. The miso on your jar is a separate ingredient, so check its label as well.