In season and beloved, ganjang gejang is not as safe from food poisoning as you might think

"If it's marinated in soy sauce, isn't it safe from food poisoning?"

Blue crabs are in season, and no dish captures the moment quite like ganjang gejang — raw crab cured in soy sauce. The combination of sweet-salty brine, rich crab meat and creamy roe has elevated the dish into a culinary destination in its own right, drawing food lovers from neighboring Japan.

Because the crabs are submerged in soy sauce and left to mature, many people assume the process keeps bacteria at bay. It does not. Ganjang gejang is eaten raw, which means the risk of food poisoning depends on how contaminated the original crab is and how carefully it is made and stored.

A 2016 study published in the International Journal of Food Microbiology confirmed that several foodborne pathogens can survive in raw crab marinated in soy sauce.

Researchers inoculated live crabs with five pathogens — E. coli O157:H7, Salmonella, Staphylococcus aureus, Listeria and Vibrio parahaemolyticus — then submerged them in soy sauce and monitored them for up to 28 days at refrigeration temperature (5 degrees Celsius) and room temperature (22 degrees Celsius). At 5 degrees, four of the five pathogens — all except Vibrio parahaemolyticus — were still detectable on day 28.

The fact that soy sauce inhibits bacterial growth is not the same as saying it kills all bacteria. Its high salinity and acidic environment can slow the proliferation of some microorganisms, but that falls well short of a sterilization process capable of eliminating pathogens entirely.

The research also found that bacteria clinging to crab tissue tended to survive the marinade environment better than bacteria floating freely in the soy sauce — a reminder that pathogens embedded in the crab's flesh, not just those in the liquid, must be taken into account.

Hygiene during production also matters. If the raw crab is already contaminated, or if cross-contamination occurs during preparation, microorganisms can persist in the finished product. A separate 2016 study examining the production processes of six manufacturers identified the handling of raw ingredients and process management as the key factors determining microbial safety.

Refrigeration, too, is not a cure-all. Keeping gejang cold slows microbial growth but does not kill pathogens that are already present.

Consumers should choose products made under hygienic conditions and, after purchase, follow the storage instructions and expiration date on the label. Leaving gejang at room temperature for extended periods should be avoided. The absence of an unusual smell or color change is not proof that the product is free of foodborne pathogens.

People with liver disease or weakened immune systems need to be particularly careful about infections from raw seafood. For them, fully cooked crab dishes are a safer choice than gejang.