Calculate D value |
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formula123
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 D-value 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 Log10 colony
forming units/ml. 2. Convert your colony forming units (CFU)/ml
values to their log10 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 log10 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 D-value 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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