Question

Cooked flavor to milk is due to .......

• A. Heat deturation of casein
• B. Heat deturation of lactalbumin
• C. Caramelization of lactose
• D. Hydrolysis of lipids

Hint:

The cooked flavor threshold in milk is closely linked to the temperature-time profile:
Heating milk above \(74^\circ\text{C}\) instantly initiates the thermal release of sulfhydryl compounds from \(\beta\)-lactoglobulin, marking the transition from a fresh to a cooked flavor profile.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
When milk is subjected to thermal treatments such as pasteurization, ultra-pasteurization, or sterilization, its flavor profile changes.
The development of a distinct "cooked" or "custard-like" flavor is a direct result of chemical changes in whey protein fractions during heating.

Step 2: Detailed Explation:
Casein, the major protein class in milk, is highly heat-resistant and does not easily deture at standard pasteurization temperatures.
On the other hand, whey proteins, which include \(\beta\)-lactoglobulin and \(\alpha\)-lactalbumin, are highly heat-sensitive.
These whey proteins contain sulfur-containing amino acids (such as cysteine and methionine) with free or masked sulfhydryl (\(-\text{SH}\)) groups.
When milk is heated above \(74^\circ\text{C}\), these whey proteins (historically referred to collectively as lactalbumin) undergo thermal deturation.
This structural unfolding exposes and releases these volatile sulfur compounds, particularly hydrogen sulfide (\(\text{H}_2\text{S}\)).
These volatile sulfur compounds are directly responsible for the characteristic cooked flavor of heated milk.
Caramelization of lactose and lipid hydrolysis occur under much more severe conditions and do not drive the initial cooked flavor of pasteurized milk.

Step 3: Fil Answer:
The correct option is (B).