Question

Minimum temperature range of heating for perceiving cooked flavour in milk is

• A. 70--74$^{\circ}$C
• B. 76--78$^{\circ}$C
• C. 80--84$^{\circ}$C
• D. 90--92$^{\circ}$C

Hint:

The cooked flavor in milk is caused by the release of active sulfhydryl compounds from \(\beta\)-lactoglobulin, which begins when heating reaches 76--78$^{\circ}$C.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
When milk is heated, thermal reactions alter its volatile profile.
The development of a "cooked" flavor is a characteristic sensory change associated with high-temperature processing.

Step 2: Detailed Explanation:
The cooked flavor in heated milk is primarily caused by the release of volatile sulfur compounds, chiefly hydrogen sulfide (\(\text{H}_2\text{S}\)).
These compounds are generated through the thermal denaturation and activation of sulfhydryl groups (\(-\text{SH}\)) present in:
1. Whey proteins, primarily \(\beta\)-lactoglobulin.
2. Proteins associated with the milk fat globule membrane (MFGM).
Under standard heating conditions with short holding times, this thermal activation of sulfhydryl groups begins when the temperature of the milk reaches 76--78$^{\circ}$C.
At this temperature, the released volatile sulfides reach concentrations that can be perceived by sensory panels as a cooked flavor.
Heating milk below this range (e.g., 70--74$^{\circ}$C) does not denature these proteins sufficiently to release detectable levels of sulfhydryl compounds, maintaining a pasteurized flavor profile.
Heating above this range (e.g., 80--84$^{\circ}$C or 90--92$^{\circ}$C) increases the intensity of the cooked flavor and can lead to caramelized or burnt off-flavors due to Maillard browning reactions.

Step 3: Final Answer:
Therefore, the minimum temperature range for perceiving a cooked flavor in milk is 76--78$^{\circ}$C.