We see that some fruits like apples, mangoes, guavas, watermelon are sweet in taste while other fruits like orange, lemon and raw mango etc. are sour in taste. Each fruit has different taste. Now here is a question that why does every fruit have a characteristic taste?
Actually, the taste of a fruit depends on the compounds present in it. Normally a fruit contains the materials like cellulose, proteins, starch, vitamins, certain acids, fructose or sugar. All these materials are found in mixed form inside the fruit and they have different proportions in different fruits. Fruits of sweet taste have more fructose in them whereas the fruits of sour taste have more acids in them. Some fruits are sweet as well as sour in taste like orange, as it has almost equal quantities of fructose and acids in it. Normally, the raw fruits have more acids but on ripening the quantity of acids get decreases and the amount of sugar gets increase. This is the reason that raw mangoes are sour in taste but on ripening they become sweet. Raw bananas have more starch but when the fruit gets ripen, the starch gets converted into fructose. The chemical changes take place inside the fruit during the process of ripening, due to these changes the amount of sugar increases in fruit and it becomes sweet. You will see that even two fruits of same type have different taste like two mangoes or two apples do not have same taste but they are different in taste. The reason behind it is that same fruit has many varieties and there is also variation in the quality of soil, manure, climate, water and technique of growing etc. These variations change the proportion of the compounds inside the fruit which causes the difference of taste. Fruits like lemons have sour taste; they do not get sweet taste even after ripening due to the presence of excessive amount of acids.