Question from a student 20160417b

Question

From: SSSSSSSS
Sent: Saturday, April 16, 2016 9:42 PM
To: hoishankwan@cuhk.edu.hk
Subject: FNSC 3180: question about 14-15 final exam QB4

Dear Professor Kwan,

I am SSSSSS from FNSC3180. You have mentioned last year exam paper question B4 on Thursday and I am confused about the answer of (e). When calculating  the D value of bacteria at 120C, 0.25min/1.5 is used. May I know that whether this is the final answer or only a step of the solution? Because I thought the equation: DT2=DT1*10[T1-T2/Z] (which was mentioned on page 62 of the note) should be used to calculate the D value of bacteria at 120C. However, if this equation is used, it will be difficult to calculate without using calculator. Could you explain how to calculate the D value of bacteria at 120C? Thank you very much.

Answer

Sorry that I made a mistake when I did the calculation. the D value of bacteria at 120C should be   0.25 min/15, because the reduction should be 1.5 log. the approximation of 1.5 log is 15. You do not need to use the equation. It is only an approximation but I accept that as the final answer.

Best,

HS Kwan