Skip to comments.Freeper Help Requested - Pasteurization Units, Calculating
Posted on 11/25/2001 8:38:06 AM PST by Jhoffa_
I have a question regarding pasteurization that no one has (thus far) been able to answer.
In a production environment, pasteurization units (Pu's) are the standard for determining pasteurization effectiveness. A pasteurization unit is equal to one minute @60° C. Depending of which bacteria you wish to kill each product is pasteurized to a specified number of PU's. The total number of Pu's are a product of both Time and Temperature.
My question is: How is the total number of PU's calculated over a production run where the times and temperatures vary?
What is the formula for accurately determining total Pu's when you have the time/temperature available?
I had thought that it was a simple matter of raising the Lethal Rate to the power of (Tempurature-base)
Example: Pu's per minute = Lt ^ (Temp - 60)
So if the Lt were, say 1.235 And the Temp were 62° You would be pulling down 1.52 Pu's per minute.
But I now have a Chart from a major manufacturer of Pasteurization Equipment and while this formula is dead accurate in the middle of the chart, error creeps in as you near the high and low temperature extremes.
So, what is the formula for calculating these Pu's accurately, regardless of temperature?
ANY HELP you can provide will be greatly appeaciated.
(It was found painted in blood on a cave wall in Tibet.)
Can anyone decipher this thing?
A pox on thee spudman!
Pasteurization was never designed to kill all microbes; the intent was to kill certain comparatively heat-sensitive microbes. Pasteur originally designed pasteurization to give the French beer industry a boost; French beer apparently turned rancid to some degree a century and a quarter ago. [Just think of it ----- French beer.] Later it was adapted, in France, to lessen the likelihood of wine turning sour.
It wasn't until the concept reached this country that it was applied to milk. In milk the purpose was to kill the tubercle bacillus. Sometime later a slightly more heat resistant organism became the criterion, the organism that causes Q fever. [Q = British for querry, i.e. question.]
That's where the lethal rate and a "D" value come in.. You are hunting specific microbes and balancing that with an adverse effect on product quality.
Can you help me with the calculation part of the problem?
Simple. If you pass wind at least one time in a warm, windless environment, the PU factor is unbearably high. Don't stop to measure it; just get the heck outa there pronto. (And as you do, motion in such a way as to cast the blame on someone else.)
Sorry bout the paper Jim.. :(
I boil all my incoming letters at 212 degrees for 15 minutes.
I'd give you a D factor for that, but I don't have the spreadsheet handy.
I remember you talking extensively about microbes, government experimentation up to and including chimneys with gas jets in them.
Know anything about Pasteurization and food safety?