Why does an apple change color when exposed to air?

1. Apples contain tannins acting as astringent agents.
2. Apples cannot contain tannins due to the presence of betacyanins.
3. Apples turn brown because of phenolic compounds.
4. Apples do not change color in air.

How many of the above statements are correct?

Question

Why does an apple change color when exposed to air?

1. Apples contain tannins acting as astringent agents.

2. Apples cannot contain tannins due to the presence of betacyanins.

3. Apples turn brown because of phenolic compounds.

4. Apples do not change color in air.

How many of the above statements are correct?

Quintessence Classes · Accepted Answer

The correct answer is Two statements only. To determine the correct answer, we need to look at the biochemical process that occurs when an apple is sliced or bruised, known as enzymatic browning.Statement 1 is Correct: Apples contain tannins, which are a type of polyphenol. These act as astringent agents (giving underripe fruit a "puckering" taste) and serve as a defense mechanism for the plant.Statement 2 is Incorrect: This statement contradicts Statement 1. Furthermore, betacyanins are pigments responsible for the deep red/violet color in plants like beets or dragon fruit; they are not the reason for an apple's composition or lack of tannins.Statement 3 is Correct: When an apple is cut, the enzyme polyphenol oxidase (PPO) reacts with oxygen and the phenolic compounds (including tannins) present in the fruit's tissue. This reaction produces o-quinones, which then polymerize to form melanin, the brown pigment.Statement 4 is Incorrect: It is a common household observation that apples turn brown (change color) when exposed to air.

Answer

One statement only

Answer

Three statements only

Answer

All four statements

Answer & Explanation

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JKPSC JKAS 2022 Prelims

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