Question

Rancid off flavor in fat rich dairy products is developed due to hydrolysis of

• A. Lactose
• B. Fat
• C. Casein
• D. Whey protein

Hint:

Dairy Degradation Pathways:
Hydrolysis of FAT $\rightarrow$ RANCIDITY (Butyric acid).
Hydrolysis of PROTEIN $\rightarrow$ Bitterness Putrefaction.
Fermentation of LACTOSE $\rightarrow$ Souring (Lactic acid).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Lipolytic hydrolytic rancidity in dairy lipids: hydrolysis of ester bonds in milk fat triglycerides by native lipoprotein lipase (LPL) or microbial lipases liberates volatile free short-chain fatty acids (butyric C4, caproic C6), imparting a pungent, acrid, rancid off-flavor.
Key Formula or Approach:
\[ \text{Milk Fat Triglyceride} + 3 \text{ H}_2\text{O} \xrightarrow{\mathbf{Lipase \text{ (Lipolysis)}}} \text{Glycerol} + 3 \; \mathbf{Free \text{ } Fatty \text{ } Acids \text{ (Butyric C4:0)}} \implies \mathbf{Rancidity} \]

Step 2: Detailed Explanation:
In dairy chemistry and quality deterioration of fat-rich dairy foods (butter, cream, ghee, whole milk powder):
- Rancid Off-Flavor (Hydrolytic Rancidity) develops directly due to the enzymatic or chemical Hydrolysis of Milk Fat (Lipids) (B):
1. Milk fat is unique among edible fats in containing high proportions of short-chain, water-soluble, volatile fatty acids (Butyric acid C4:0, Caproic acid C6:0, Caprylic acid C8:0, and Capric acid C10:0).
2. When milk fat is hydrolyzed by Lipases (native milk lipoprotein lipase or heat-stable psychrotrophic bacterial lipases), these free short-chain fatty acids are released.
3. Free Butyric Acid has an exceptionally low sensory threshold ($< 5 - 10\text{ ppm}$), producing the sharp, acrid, pungent, vomity, and distinct rancid off-flavor.

Step 3: Final Answer:
Hence, rancid off flavor develops due to hydrolysis of Fat, matching option (B).