The stinky microbiome of stinky tofu

Contributed by Poyin Chen

Having just returned home from a two week trip to Taiwan, my mind is still on all of the delicious Taiwanese food I am now suddenly deprived of—particularly stinky tofu. And what better way to ease back into lab work than by pondering the scientific causes behind stinky tofu’s “flavor”?

Traditionally, stinky tofu is first prepared by fermenting a mixture of vegetables and meats in a brine solution. All organisms involved in this fermentation process are introduced by the organic matter in the brine, leading to differences in flavor profile by batch and production location. To understand the composition of the stinky tofu microbiome and metabolome, Gu et. al. collected stinky tofu and respective brine samples from different regions of China for DNA sequencing and analysis of biogenic amine (aka stinky flavor) composition. Microbes were identified based on their 16S sequences and biogenic amines were characterized using HPLC.

This study found that while the majority of the tofu and brine microbiomes were composed of bacteria (80%)—namely lactic acid bacteria (64%)—a significant portion of the microbiome also included fungi (20%). Due to the differences in microbiome composition between locations, there were observable location-specific differences in biogenic amine composition. Interestingly while lactic acid bacteria are known for their roles in flavor compound production, specific biogenic amine profiles could not be correlated to lactic acid bacteria composition in these samples. These results suggest that flavor production is more bacterial strain-specific rather than genus or species specific.

So what does this all mean?

  1. There are A LOT of bacteria, yeast, and other fungi in uncooked stinky tofu.
  2. The majority of these bacteria can also be found in fecal matter and cheese.
  3. Different stinky tofu producers will have slightly differently flavored stinky tofu.
  4. Stinky tofu is still delicious!

Reference: https://doi.org/10.1016/j.lwt.2017.08.085

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