Question

Which of the following are oxidized flavour defects of ghee
(A) Tallowy
(B) Fishy
(C) Soapy
(D) Metallic

• A. (A), (B) and (C) only.
• B. (A), (B) and (D) only.
• C. (A), (B), (C) and (D).
• D. (B), (C) and (D) only.

Hint:

Flavor defects are classified into two groups:
- Oxidative Rancidity: Tallowy, Fishy, Metallic, Cardboardy.
- Hydrolytic Rancidity: Soapy, Bitter, Pungent.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Oxidized flavor defects in high-fat dairy products like ghee are caused by lipid autoxidation.
This reaction involves the oxidation of unsaturated fatty acids, generating volatile secondary carbonyl compounds that impart specific off-flavors.

Step 2: Detailed Explanation:
Let us analyze each of the listed flavor defects:
1. Tallowy (A): This is a classic oxidized flavor defect.
It is caused by the autoxidation of saturated and unsaturated fatty acids, yielding aldehydes and ketones that produce a flavor resembling animal fat or tallow.
2. Fishy (B): This oxidized defect occurs when ghee contains trace amounts of moisture and lecithin (phospholipids).
The oxidation of lecithin yields volatile compounds like trimethylamine and specific unsaturated aldehydes, producing a distinct fish-like off-flavor.
3. Metallic (D): This defect occurs during the early stages of lipid oxidation.
It is primarily caused by the compound oct-1-en-3-one, which has an extremely low flavor threshold and imparts a distinct metallic or copper-like taste.
4. Soapy (C): This is a hydrolytic rancidity defect, not an oxidative one.
It is caused by the lipase-catalyzed hydrolysis of triglycerides, which releases free short- and medium-chain fatty acids.
In the presence of alkaline salts, these acids form sodium soaps, producing a soapy taste.

Step 3: Final Answer:
Tallowy (A), Fishy (B), and Metallic (D) are oxidized flavor defects, which corresponds to (A), (B) and (D) only.