Calculate D value 
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Admin
Admin Group Administrator Joined: 01 Sep 2009 Location: N. Ireland Status: Offline Points: 390 
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Posted: 11 Feb 2012 at 11:37pm 
Welcome back. I am going to explain how to do this by calculating the slope of the thermal death curve for the organism you have studied using an Excel function called "slope". The Dvalue is then obtained by obtaining the negative reciprocal of the slope. 1. I presume that you have these values
in an Excel spreadsheet? If not create a workbook with 3 columns, Time
(minutes), Colony forming units/ml, and Log_{10 }colony
forming units/ml. 2. Convert your colony forming units (CFU)/ml
values to their log_{10 }equivalents. 3. Excel 2010 has a useful slope
function to calculate the slope of the linear regression line for x and y
values and I will explain how to use this function. 4. Lets assume that your time values (x
values) are in column A and range from A2 to say A15 and the corresponding log_{10 }colony
forming units/ml are in column C and range from C2 to C15. The slope can then
be calculated using =slope(C2:C15, A2:A15). 5. The Dvalue is obtained by obtaining
the reciprocal of the slope and multpling this value by 1. _{} 

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mstrange
Newbie Joined: 30 Nov 2010 Status: Offline Points: 4 
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Hi again!
Got table of time (mins) and nos of survivors at 200F. Pl can you tell how to calculate D at 200F? Thanks.


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