The presence of which of the following causes the bitter or sharp taste of unripe fruits?

Unripe fruits contain organic acids such as citric, malic, tartaric, and oxalic acids that give them their characteristic sharp, sour, or bitter taste. As fruits ripen, these acids break down and are converted into sugars, making the fruit sweeter. Starch is tasteless, carotenoids provide pigmentation, and lipids are fats.