How to calculate spoilage rate in canning 
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scotty
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Posted: 22 Mar 2010 at 10:56pm 
Good to see the Fo calculator. Tnks! 

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michael
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Scotty
It is fairly easy to calculate the number of surviving microorganisms in a canning process. I say fairly easy since a knowledge of both the effects of heat on microorganisms and maths, probability and logarithms in particular, is required! The critical equation has been described by Stumbo* in his well known book on 'Thermobacteriology in food processing': t = D(log a  log b) D= decimal reduction time (minutes) at a reference temperature for target organismtime to reduce the population by 90% t= total equivalent time in minutes at reference temperature a= initial microbial load b= number of surviving microorganisms. Using this equation one can predict the probability of one or more cans spoiling, this can be adjusted for 100, 1000, or whatever number you want. I have developed a simple model which shows how to do this and enables D and other values to be varied. The URL is at www.dairyscience.info/newCalculators/probability.asp You dont say what your problem is. If the spoilage rate is in excess of the predicted one then you have a problem. This might be caused by ingress of contaminated cooling water, check residual chlorine levels; defective seams; inadequate processing; high spore loads. *Stumbo, C. R. (1973) Thermobacteriology in food processing. Second edition. Academic Press, New York and London. 

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