When it comes to taste, there are five confirmed categories: sweet, sour, salty, umami, and bitter.

Though it is generally thought that the latter of these generally applies to foodstuffs that were once a threat – hence our taste buds evolved to not be particularly fond of them on first try – the overall knowledge of bitter compounds is still not fully understood.

We may have had bitter taste receptors for 500 million years, but we still don’t know much about the compounds that cause these receptors to react in our tongues.

However, researchers at the Leibniz Institute for Food Systems Biology at the Technical University of Munich in Freising and the Leibniz Institute of Plant Biochemistry in Halle (Saale) have been working to revolutionise our understanding of how bitter taste works.

And, as they reveal in a paper recently published in the Journal of Agricultural and Food Chemistry, three previously undiscovered bitter compounds come from the same unlikely source.

In their research, the team point out that our ideas of bitterness equalling toxicity are misunderstandings, since bitter compounds aren’t always dangerous, and dangerous compounds aren’t always bitter.

Thus, as researcher Maik Behrens explains in a statement, further research is required to truly complete the BitterDB database and allow us a comprehensive understanding of bitter molecules and receptors:

“Comprehensive data collections on bitter compounds and their receptors could help us to find answers to these open questions. The more well-founded data we have on the various bitter compound classes, taste receptor types and variants, the better we can develop predictive models using systems biology methods to identify new bitter compounds and predict bitter taste receptor-mediated effects. This applies to both food constituents and endogenous substances that activate extraoral bitter taste receptors.”

To expand the world’s knowledge of bitter compounds, the team turned to the world of fungi and the Bitter Bracket mushroom (Amaropostia stiptica).

Of course, you’d expect just from its name that this mushroom is, in fact, quite bitter. And it did not disappoint, with the mushroom presenting the researchers with three previously unknown bitter compounds, and one of the most bitter things ever tasted.

Interestingly though, this mushroom is safe to eat, so long as you don’t mind an unpleasant experience.

Amid their other findings, the team isolated bitter compound oligoporin D, which stimulates the bitter taste receptor type TAS2R46 even at extremely low concentrations, and added this and the other incredibly bitter compounds to the BitterDB, as Behrens continued:

“Our results contribute to expanding our knowledge of the molecular diversity and mode of action of natural bitter compounds. In the long term, insights in this area could enable new applications in food and health research, for example in the development of sensorially appealing foods that positively influence digestion and satiety.”

But why is this mushroom so bitter if it’s not toxic? Well, unlike some poisonous mushrooms which don’t taste bad at all, the research team point out that perhaps this is the result of a predator other than humans, with the mushroom adapting not to our tastebuds but to one of the many other creatures that might consume them.

If you thought that was interesting, you might like to read about the mysterious “pyramids” discovered in Antarctica. What are they?