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# Microbiology D-Value question

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### #1 emiree88

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Posted 12 August 2010 - 08:13 AM

Hi, as far as I'm aware D-Value represents the death of 90% of organisms, however I have no idea how to calculate this table, so any advice will be much appreciated.

Question: Determine the D-value at each temperature. [If it helps: Spore suspensions of Bacillus cereus]

Edited by emiree88, 12 August 2010 - 08:13 AM.

### #2 bob1

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Posted 12 August 2010 - 12:49 PM

I think you need to graph it and do a bit of extrapolation!

### #3 gebirgsziege

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Posted 13 August 2010 - 12:10 AM

Agree with bob1.

Try asking yourself the question the other way round: Spores at t0=100%; how long does it take until only 10% of spores are surviving.
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### #4 emiree88

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Posted 13 August 2010 - 04:15 AM

Okay so I've created three separate graphs for each temperature, put a linear regression line... Now I'm still lost. Do I simply fill in the blanks and assume those to be D-values (Which makes no sense) or do I get the 10% (90% Dead) of the first value, and assume that to be the D-value, and mark that on the graph?

### #5 bob1

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Posted 15 August 2010 - 04:40 PM

Use the equation of the line to predict the time where there is only 10% of the start number (100%) of the cells left.