Some foods will have a bitter taste. Here are some common examples:

Bitter gourd: Bitter gourd is a common vegetable, rich in flavonoids, which makes it bitter.

Coffee: The bitterness of coffee comes from the caffeine contained in it, which some people think is the charm of coffee.

Grapefruit: Grapefruit is rich in flavonoids, which makes it bitter.

Olive: Olive is a healthy food, but it also has a bitter taste.

Generally speaking, bitterness is not acceptable to everyone, but in some delicacies, bitterness is regarded as a unique delicacy.