Question

Which is not true regarding propionic acid?

• A. It is effective against molds
• B. It affects cell membrane permeability
• C. It is a long chain fatty acid
• D. It is less effective against yeast and bacteria

Hint:

Propionic acid has only 3 carbons ($C_3$).
Sorbic acid has 6 carbons ($C_6$), and benzoic acid has 7 carbons ($C_7$).
All of these organic acid preservatives are short-chain structures, not long-chain fatty acids.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Propionic acid and its calcium/sodium salts are widely used food preservatives, particularly in the baking industry.
Key Principle:
The physical structure and chemical properties of fatty acids (such as chain length) dictate their biochemical classification and physiological effects.

Step 2: Detailed Explation:
Propionic acid has the chemical formula $CH_3CH_2COOH$.
With a structure containing only three carbon atoms, it is classified as a short-chain fatty acid (SCFA).
Long-chain fatty acids (LCFAs) typically contain 12 or more carbon atoms.
Therefore, statement (C), which asserts that propionic acid is a long-chain fatty acid, is chemically incorrect.
Regarding its antimicrobial properties:
Propionic acid is highly effective against molds (A), making it the preservative of choice for breads and cakes to prevent spoilage and rope.
It functions by penetrating microbial cell walls in its undissociated form, altering cell membrane permeability (B) and accumulating inside the cytoplasm to disrupt metabolic functions.
Additiolly, it is turally less effective against yeasts and many bacteria (D).
This selective toxicity is beneficial in baking, as it allows baker's yeast (*Saccharomyces cerevisiae*) to ferment the dough effectively without being inhibited by the preservative.

Step 3: Fil Answer
The incorrect statement is (C), because propionic acid is a short-chain fatty acid rather than a long-chain fatty acid.