One more past exam paper question from students

It is not unreasonable for 1000D. Heat treatment can target some microorganisms with a larger D value and the other microorganisms with small D value will get very large Ds in the treatment.

Best,

HS Kwan

-----Original Message-----
From: vvvvvvvvvvvvvvvvv
Sent: Friday, May 04, 2012 6:12 PM
To: b097709@mailserv.cuhk.edu.hk
Subject: Questions on D-value calculations

Dear Professor Kwan,

I would like to ask about the calculation question on the 2010 past paper

question 12b. 

The question asks to calculate the number of D's and I assumed it is calculated

by dividing the process time (i.e. 10min) by the D-value of microbe at pH5.0

(i.e. 0.01min for spoilage bacteria).  However, the outcome of 10/0.01 is 1000.

 It seems to be unreasonable to have 1000D, so I wonder where is my mistake in

the calculation.