Question

The heat stability of milk is assessed by plotting the graph of:

• A. Heat coagulation temperature vs. time
• B. Heat coagulation time vs. temperature
• C. Heat coagulation time vs. pH
• D. Heat coagulation time vs. redox potential

Hint:

The standard test for milk heat stability involves plotting the "HCT-pH profile" at $140^\circ\text{C}$.
This curve helps identify how milk proteins behave under thermal stress at different acidities.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Heat stability of milk refers to its ability to withstand high processing temperatures without undergoing coagulation or gelation.
It is a crucial parameter in the manufacturing of sterilized milk, evaporated milk, and ultra-high-temperature (UHT) treated dairy products.

Step 2: Detailed Explanation:
The heat stability of milk is experimentally determined by measuring the Heat Coagulation Time (HCT), which is the time required for milk to show visible signs of coagulation when heated at a constant high temperature (typically $140^\circ\text{C}$).
Because the stability of milk proteins (especially casein micelles) is highly sensitive to charge and acidity, the HCT is strongly dependent on the pH of the milk.
Scientists assess and characterize the heat stability of different milk samples by plotting a graph of Heat Coagulation Time (HCT) versus pH.
This plot typically shows a characteristic curve with a maximum stability peak (usually around pH 6.7) and a minimum stability trough (around pH 6.9).
Therefore, the heat stability of milk is assessed by plotting the graph of heat coagulation time vs. pH.

Step 3: Final Answer:
The heat stability of milk is assessed by plotting the graph of heat coagulation time vs. pH.