Question

Name the substance which makes the fruit sour?
A.Acids
B.Bases
C.Salts
D.None of these

Answer 1

Hint: Generally, acids are found to taste sour due to the presence of the sour hydrogen ion and bases are found to taste bitter due to the presence of the hydroxyl ions. But they can also have other tastes depending on the part of the molecule. On the other hand, salts have a salty taste.

Complete step by step answer:
-If a fruit tastes sour, then it is mainly because of the presence of acids in it. The two main organic acids which are accumulated in fruits and cause the sour taste are malic acid and citric acid.
-The citrus fruits like oranges, grapes, limes and lemons contain more citric acid while other fruits like apples, watermelons, pears etc. contain more malic acid.
-The citric acid in fruits may get accumulated in two ways. One way is that the citric acid is not formed in the fruit, but transported to the fruit and then the fruit acts like a storage organ. The other way is that the carbohydrates or sugars present in the fruit get converted into the organic acid.
-The accumulation of malic acid is also similar. The pH of the transporting organs of the fruit plants is 7 or higher. So, the malic acid gets produced in the fruit itself.

So, the correct option is A.

Note:
-The function of malic acid and citric acid is to act as intermediates in the malate and citric acid cycle which is mainly for respiration. Therefore, they occur in the metabolism of almost all living beings.
-Of all the acids, malic acid has the sharpest taste and so it is used to flavor sour candies.
-Another common acid found in fruits is tartaric acid particularly in grapes and avocados. It is used predominantly in wines to give a strong and distinctive flavor.