Question

Sodium benzoate finds applications in

• A. Perfumes
• B. Nylon 6,6
• C. Soaps and detergents
• D. Food preservatives

Hint:

Standard NCERT food preservatives:
- Sodium benzoate (\(\text{C}_6\text{H}_5\text{COONa}\)) is the most widely used chemical food preservative.
- Salts of sorbic acid and propanoic acid are also commonly used.

Answer 1

The Correct Option is D

Concept:
Chemical substances added to food items to prevent spoilage caused by microbial growth (such as fungi, bacteria, and yeasts) or undesirable chemical alterations are called food preservatives.

Step 1: Chemical Structure and Properties of Sodium Benzoate:
Sodium benzoate is the sodium salt of benzoic acid, having the molecular formula \(\text{C}_6\text{H}_5\text{COONa}\).
It is a white, odorless crystalline powder that dissolves readily in water, unlike benzoic acid itself, which is sparingly soluble.

Step 2: Mechanism of Action as a Food Preservative:
In acidic food matrices (such as carbonated soft drinks, fruit juices, jams, and pickles), sodium benzoate converts to lipophilic undissociated benzoic acid.
Benzoic acid readily diffuses across microbial cell membranes, lowering the intracellular pH and inhibiting phosphofructokinase and cellular metabolism, thereby inhibiting the proliferation of molds, yeasts, and bacteria.
Because it is metabolized in the human liver by conjugation with glycine to form non-toxic hippuric acid, which is excreted in urine, it is safe for human consumption within regulatory limits.

Step 3: Verification of Other Options:
- Perfumes primarily use fragrant volatile esters and essential oils, not sodium benzoate.
- Nylon 6,6 is synthesized by condensation copolymerization of adipic acid and hexamethylenediamine.
- Soaps are sodium or potassium salts of higher fatty acids (such as stearic, palmitic, and oleic acids).
Final Answer:
Sodium benzoate is used as a food preservative, corresponding to option (D).