Cats are technically not capable of tasting spicy foods in the way that humans do. This is primarily because of how different species' taste receptors, which are primarily located on the tongue, function.
In humans, the sensation of spiciness is not actually a taste, but rather a pain signal. The component in hot peppers that leads to the sensation of spiciness is called capsaicin. Capsaicin binds with pain receptors in the mouth and throat, specifically the TRPV1 receptor, which usually responds to heat. In this case, these receptors send a signal to the brain indicating the presence of heat, even though the actual temperature has not increased, leading to the sensation of hotness or spiciness. In other words, the "taste" of spicy food is actually a type of chemical-induced pseudothermia.
Cats and many other animals have the TRPV1 receptor, so they would likely experience a pain response if they consumed capsaicin. However, there's a critical difference: cats are obligate carnivores and have a markedly different sense of taste compared to humans and other omnivores or herbivores. Specifically, they lack the taste receptors for sweetness, which are part of the T1R family of taste receptors.
This evolutionary adaptation is likely a result of their meat-centric diet. The absence of a need to detect sweet plant-based foods has meant that cats' taste receptor repertoire has altered over time.
While capsaicin doesn't fall into the sweet category, the streamlined sense of taste in cats means they don't perceive flavors the same way we do. So their experience of capsaicin, if they have one, would likely be different than ours. Furthermore, because capsaicin is relatively non-toxic, it's unlikely to cause significant harm to a cat beyond momentary discomfort or irritation, though in very high quantities it could potentially lead to more serious issues like gastrointestinal damage.
However, we must remember that this conclusion is largely based on inferential and extrapolated data. Direct studies on how cats-or most animals-experience capsaicin or other pungent compounds are sparse, mainly because of ethical considerations related to causing potential distress to research animals.
In conclusion, while it's probable that cats would react adversely to consuming capsaicin due to activation of pain receptors, their lack of receptors for sweet (and by proxy, limited taste capabilities) means they probably don't precisely "taste" spicy foods as humans do. As responsible pet owners, it's advisable to keep spicy foods out of cats' diets to avoid any potential discomfort for them.