The phenomenon that cilantro sometimes tastes like soap to certain individuals is due to genetic differences in taste perception. This is known as cilantro or coriander aversion.
The aversion to the taste of cilantro has a genetic basis and is related to how certain chemical compounds present in cilantro are perceived by specific taste receptors on the tongue. One of the compounds responsible for this peculiar flavor is called hexenal acid, which is found in higher amounts in cilantro compared to other aromatic herbs.
Some people possess a genetic variant that makes them more sensitive to the chemical compounds present in cilantro, especially hexenal acid. For these individuals, hexenal acid can have an unpleasant taste reminiscent of soap. These genetic differences in taste perception result in some people enjoying cilantro and finding it delicious, while others find it repulsive.
It's important to note that this aversion to the taste of cilantro is not universal and varies among different populations and cultures. In some cultures, cilantro is widely used and appreciated in cooking, while in others, it is avoided due to its peculiar flavor.