Physio Ex. 8.0: Does freezing have effect in the pepsin digestion?

Exercise 8: Digestion
Activity 3

Q4. Would freezing have the same effect? Why or why not?
This question was referring to the previous questions on the effect of the enzyme activity, which I answered that the boiling lowered the pH, making it more acidic. I am going to assume freezing will not have the same effect as to boiling, but I cannot reach a reasonable conclusion why it wouldn't.

Q5. Which test tubes were your 'controls' and what are they controlling for?

I'm going to guess tubes 1, 3, and 4. Not sure what they are suppose to control for. The pH.

For my results of the computer stimulation:
Tube 1 (boiled; pepsin, BAPNA, ph 2 buffer) - 0
Tube 2 (pepsin, BAPNA, ph 2 buffer) - 0.40
Tube 3 (pepsin, deionized water, ph 2 buffer)- 0
Tube 4 (deionized water, BAPNA, ph 2 buffer) -0
Tube 5 (pepsin, BAPNA, ph 7 buffer) - 0.03
Tube 6 (pepsin, BAPNA, ph 9 buffer)- 0

Could someone verify me