The correct answer is: Potassium metabisulphite.
Potassium metabisulphite is a food additive used as a preservative. It is a white, odorless powder that is soluble in water. Potassium metabisulphite is used to prevent the growth of microorganisms in food, such as bacteria, yeast, and molds. It is also used to prevent browning in fruits and vegetables.
Potassium metabisulphite is a safe food additive when used in accordance with good manufacturing practices. However, it can cause allergic reactions in some people. It is also important to note that potassium metabisulphite can interact with certain medications, so it is important to talk to your doctor before using it.
The other options are incorrect because they are not food additives. Potassium is a mineral that is found in many foods, such as bananas, potatoes, and meat. Calcium is a mineral that is found in many foods, such as milk, cheese, and yogurt. Sulphur is a mineral that is found in many foods, such as eggs, meat, and fish.