Probiotic contents don’t change in vegan kimchi

Kimchi, the traditional Korean fermented cabbage dish with a growing reputation for probiotic goodness, has always been off the menu for vegans and vegetarians because one of its core ingredients is derived from fish.

Surprisingly, however, new research reveals that making the product without including animal derivatives results in an almost identical bacterial payload.

A team led by microbiologist Michelle Zabat of Brown University in Rhode Island, US, measured the bacterial communities active in traditionally made kimchi and a variant in which the usual fish sauce base was replaced by miso, a Japanese paste made from fermented soybeans.

To make their findings, the researchers took samples from the traditional and vegan versions at the start, middle and end of the fermentation. They also took swabs from the facility used to produce both. All the samples were then subjected to high-throughput DNA-sequencing to identify the bacteria present.

As expected, at the start of fermentation the microbial loads were very different. By the end of the process, however, the communities were near-identical, and dominated by two genera known to thrive in fermented cabbage, Lactobacillus and Leuconostoc.

This was a surprise, because miso is itself a microbially rich foodstuff.

“The fact that those bacteria were lost almost immediately during the fermentation was surprising,” says co-author Peter Belenky. “We thought they’d carry over to the kimchi, but they didn’t.”

He speculates the quick die-off was because as the kimchi fermented its salt level decreased, impacting on the salt-tolerant species found in soybean paste.

“If we made really salty kimchi,” Belenky adds, “we might see them.”

At the start of fermentation Lactobacillus and Leuconostoc species were present only in very small quantities, but by the end they comprised the entire community.

Interestingly, however, they were also found to be present in large amounts in the bacterial swabs taken from around the production facility. The researchers note that the study did not determine whether this was because they had transferred from the kimchi, or whether the processing plant in effect provided the starter-culture for the food.

Research suggests that probiotic bacteria play a positive role in human and animal health, primarily by reducing the ability of gastrointestinal pathogens to take up residence. However, many scientists are concerned about a lack of firm evidence regarding particular strains and doses.

To the extent that their benefits exist, however, vegans and vegetarians now have a potentially rich new source.

The research is published in the journal Food Microbiology.