Production of sulphur dioxide gas which destroys and prevents the entry of microorganisms in food, is brought about by the addition of :

Question

Accepted Answer

Option 3, Potassium metabisulphite, is the correct answer for the production of sulphur dioxide gas, which is used to destroy and prevent the entry of microorganisms in food. Here's why:

1. **Explanation for Option 3 (Potassium metabisulphite):**
   - Potassium metabisulphite is a chemical compound that, when added to food, releases sulphur dioxide gas. This gas acts as a preservative by inhibiting the growth of bacteria, yeasts, and molds, thereby extending the shelf life of food products. Sulphur dioxide is particularly effective in preserving dried fruits, wines, and some beverages. Its antimicrobial properties make it a popular choice in the food industry for preventing spoilage and maintaining food quality.

2. **Why the other options are incorrect:**

- **Option 1 (Potassium benzoate):**
     - Potassium benzoate is a preservative that is effective against yeast and molds, but it does not release sulphur dioxide gas. It works by lowering the pH of food products, which inhibits microbial growth. However, it is not used for the production of sulphur dioxide gas.

- **Option 2 (Sodium benzoate):**
     - Similar to potassium benzoate, sodium benzoate is used as a preservative to inhibit the growth of bacteria, yeast, and fungi. It is commonly used in acidic foods like salad dressings, carbonated drinks, and fruit juices. However, it does not produce sulphur dioxide gas and therefore does not serve the same function as potassium metabisulphite.

- **Option 4 (Citric acid):**
     - Citric acid is a natural preservative and is used to add an acidic or sour taste to foods and beverages. It is effective in controlling the pH level of food products, which can help inhibit microbial growth. However, it does not release sulphur dioxide gas and is not used for the same purpose as potassium metabisulphite.

In conclusion, potassium metabisulphite is the correct choice for the production of sulphur dioxide gas, which is essential for preventing microbial contamination in food products. The other options, while they have preservative qualities, do not produce sulphur dioxide gas and therefore do not fulfill the same role.