Which of the following pigments causes the red colour in onions?

Anthocyanins

The correct answer is Option (2)- Anthocyanins

The red color in onions is primarily caused by Anthocyanins.

Explanation:

• Carotenoids: Typically responsible for orange, yellow, or red colors, but not the primary pigment in red onions.
• Anthocyanins: These water-soluble pigments are responsible for red, purple, or blue colors in many fruits, vegetables, and flowers, including the red color in onions.
• Chlorophylls: Responsible for green color in plants but not associated with the red color in onions.
• Betalains: Another group of pigments found in beets, for example, but not the primary pigment in red onions.

In red onions, the presence of anthocyanins contributes to their red color, and the intensity of the color can vary depending on the pH of the onion cells.