Question

Increase in BR reading of ghee, when adulterated with other fats are due to ________

• A. Decrease in lower chain fatty acids
• B. Increase in lower chain fatty acids
• C. Decrease in higher chain fatty acids
• D. Decrease of unsaturated fatty acids

Hint:

The refractive index of fat increases with longer carbon chain lengths and higher unsaturation. Thus, any adulteration that replaces short-chain butyric acid with long-chain fatty acids will increase the BR reading of ghee.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The Butyro-Refractometer (BR) reading measures the refractive index of milk fat (ghee), which is influenced by the chain length (molecular weight) and degree of unsaturation of its constituent fatty acids.

Step 2: Detailed Explanation:
- Ghee is naturally unique because it contains a exceptionally high proportion of short-chain (lower chain) saturated fatty acids (such as butyric, caproic, caprylic, and capric acids).
- Lower chain fatty acids have low refractive indices, which keeps the baseline BR reading of pure ghee low (usually between 40 and 43 at \(40^\circ\text{C}\)).
- Adulterating agents like vegetable oils, hydrogenated fats (vanaspati), or animal body fats (beef/pig tallow) contain almost no short-chain fatty acids, consisting primarily of long-chain (higher chain) fatty acids.
- Adding these adulterants decreases the proportion of lower chain fatty acids in the mixture, which increases the average molecular weight and elevates the BR reading.

Step 3: Final Answer
The increase in the BR reading of adulterated ghee is due to the decrease in lower chain fatty acids.