Q. Bitter Taste?

Bitterness is an inherent property of a substance. It is due to substances such as alkaloids present in food. For example, tannins present in tea, coffee, fruits and vegetables. Tannins are desirable in tea and coffee to some extent but not in fruits and vegetables. Apple juice, if left outside, gives a bitter taste due to the tannins present in it. Some electrolytes are also bitter e.g. magnesium (Mg), ammonia (NH3) and other nitro compounds. More the number of nitro compounds, higher will be the bitterness perceived. Various amides are also bitter for example, benzamide and glycosides. Quinine, (found in grapes and  citrus fruits) marring in (grape fruit), lemonin (citrus fruits), thromine, bromide, caffeine  (coffee), Mg, NH₄, Ca, picric acid and various nitro groups are the compounds  responsible for the bitter taste. Certain phenyl groups are also responsible for bitter taste, urea also gives bitter taste.

Debittering of these citrus fruits can be done by using advanced techniques such as super critical fluid extraction. What is this technique? CO₂ at super critical pressure and temperature causes extraction of these bitter components from these substances.