Why do we feel a slightly bitter aftertaste after having sugary foods?

— Jesica Sandhu, New Delhi

A: Not everyone senses a bitter aftertaste after eating sweet foods but some do. There are a few reasons.

First, sweet foods activate your sweet taste receptors but not your bitter taste receptors. But once the sweet food has passed, the sweetness receptors become less responsive for a short amount of time. However, your bitterness receptors are still sensitive, and the taste of the normally faint bitter compounds in your saliva or other lingering food particles can become more noticeable.

Another reason is that many sugary foods also include ingredients with bitter notes, but which the sugar can mask. Common examples include cocoa (chocolate), caramelised sugars, coffee extracts, and artificial flavours.

Next, oral bacteria may rapidly metabolise leftover sugars to produce acids. Acids are generally sour but they can interfere with how you perceive other tastes, which can also be accentuated by the dryness in your mouth after eating something sweet.

Finally, some people are supertasters and perceive bitter compounds more intensely than others, so they will also be more likely to notice a bitter finish after sweet foods. This ‘ability’ depends on the TAS2R2 taste receptor genes.

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