Which acid is present in abundance in oranges and lemons?

Oranges, lemons and other citrus fruits contain a large amount of citric acid, which gives them their sour taste. Lemons have the highest amount, followed by limes, grapefruits and oranges.

Citric acid is a weak organic acid. It is also produced in the cells of all living organisms as part of the citric acid cycle (Krebs cycle), a key step in releasing energy from food during respiration. It is widely used in the food and drink industry as a natural preservative and to add a sour flavour to soft drinks, sweets and jams. It is also used in cleaning products and in medicines. Citrus fruits are also rich in vitamin C, whose chemical name is ascorbic acid, and a lack of vitamin C causes the disease scurvy.

Many natural substances contain acids. Some important ones are:

• Tamarind and grapes: tartaric acid.
• Apple: malic acid.
• Tomato and spinach: oxalic acid.
• Curd and sour milk: lactic acid.
• Vinegar: acetic acid.
• Ant sting and nettle sting: formic (methanoic) acid.
• Stomach: hydrochloric acid.
• Tea: tannic acid.

Acids are substances that taste sour, turn blue litmus red, and release hydrogen ions (H+) in water. Their pH value is less than 7. Strong acids, such as hydrochloric, sulphuric and nitric acid, are mineral acids, while the acids found in plants and animals, such as citric and acetic acid, are organic acids, which are generally weak.

Why not the other options?

• ✗Tartaric acid is found in grapes and tamarind.
• ✗Oxalic acid is found in spinach and tomatoes.
• ✗Lactic acid is found in curd and sour milk.