Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.
The pH will decrease (become less than 6) as milk turns into curd. Fresh milk has a pH of 6, which is slightly acidic since values less than 7 on the pH scale represent acidic solutions.
As milk turns into curd, it becomes more acidic. The pH scale (0-14) gives the measure of hydrogen ion concentration in a solution. Since lower pH values indicate higher acidity, the pH decreases during curd formation as the acidic content increases.
Explanation
This question tests understanding of the pH scale and how acidity changes during curd formation. The textbook context establishes that pH values less than 7 represent acidic solutions, and fresh milk at pH 6 is slightly acidic. When milk turns into curd, lactic acid is produced, increasing the hydrogen ion concentration. According to the pH scale explained in the context, higher hydrogen ion concentration means lower pH value. The reference to Question 12 in the context also supports this - it mentions that making milk alkaline delays curd formation, implying that curd formation is associated with acidic conditions.
Solution Steps
Step 1: Identify that fresh milk has pH 6, which is acidic (less than 7).
Step 2: Understand that curd formation increases acidity.
Step 3: Apply the pH scale rule - lower pH means higher acidity (more H⁺ ions).
Step 4: Conclude that pH will decrease below 6 as milk turns into curd.