A bit on Bitterness
How bitter taste receptors shaped our survival and flavour experience
Bitter taste receptors on our tongue play a fascinating and vital role in how we experience food and drinks.
Our ability to detect bitterness evolved as a defense mechanism: many potentially harmful plant-derived compounds are bitter, so detecting bitterness allowed early humans to avoid toxins.
Humans are equipped with around 25 functional bitter taste receptors genes (the TAS2R family) expressed in taste cells. This far exceeds the number of dedicated sweet or salty taste receptors, reflecting the evolutionary importance of identifying a wide array of bitter (and potentially harmful) substances.
Yet, the complexity of bitter taste extends beyond survival. That richness allows us to appreciate a spectrum of bitterness: from the subtle bitterness of certain vegetables to the sharp bite of dark chocolate, or the complex and depth a of robust coffee.
By contrast, sweet and salty tastes are associated with nutrients critical for our survival: sweetness signals sugars (energy source), and saltiness signals sodium (essential for fluid balance and nerve function). Because their presence is beneficial fewer receptors types suffice.
In culinary and drinks context, bitterness now plays a key role in adding complexity and depth. Whether through a well-crafted artisanal beer, a piece of dark chocolate, or a rich espresso, bitterness introduces sophistication to our flavour palette.
But why and how that works?
Bitterness contributes depth because it activates a broader and more diverse set of taste receptors than any other basic taste (as we have around 25 different bitter receptors, each tuned to detected different classes of bitter compounds).
This diversity produces a wider and more complex pattern of neural signals compared with sweetness or saltiness, which rely on fewer receptors types. The brain interprets this richer patterns as greater internal variation within the taste, which we perceive as nuance. In practical terms, bitterness rarely appears as a single uniform note. Instead, it often carries gradations (sharp, earthy, herbal, roasted, vegetal, or dry), depending on which receptors are activated. This receptors-level complexity is a core scientific reason bitterness feels more layered than other tastes.
Bitterness also adds depth through its interaction with other tastes. Bitter compounds can suppress sweetness, sharpen the perception of acidity, and create contrast within a drink or food. These interaction prevent flavour from becoming uniform and introduce small shifts that the palate detects over time.
Because many bitter compounds clear more slowly from the mouth than sweet or acidic molecules, they also create a longer finish, allowing other tastes and aromas to unfold against a stable backdrop. This combination (receptors diversity, cross-interaction with other tastes, and longer persistence) produce a sense of structure, which adds depths and complexity to the overall sensory experience.