Free Republic Browse · Search News/Activism Topics · Post Article

Freeper Help Requested - Pasteurization Units, Calculating
Moi | Jhoffa_X

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?

Thank You.

KEYWORDS:
first 1-2021-32 next last

1 posted on 11/25/2001 8:38:06 AM PST by Jhoffa_

To: Jhoffa_
This may be the formula.

(It was found painted in blood on a cave wall in Tibet.)

Can anyone decipher this thing?

2 posted on 11/25/2001 8:44:55 AM PST by Jhoffa_

To: Jhoffa_
E=MC2 (sorry, I couldn't resist)
3 posted on 11/25/2001 8:49:14 AM PST by AngrySpud

To: AngrySpud
Ahhh!

A pox on thee spudman!

4 posted on 11/25/2001 8:55:48 AM PST by Jhoffa_

To: Jhoffa_
A little background:

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.]

5 posted on 11/25/2001 9:01:27 AM PST by curmudgeonII

To: curmudgeonII
Pasteurization was never designed to kill all microbes; the intent was to kill certain comparatively heat-sensitive microbes.

Exactly, yes.

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?

6 posted on 11/25/2001 9:05:04 AM PST by Jhoffa_

To: Jhoffa_
What are you trying to do, make beer or anthrax?
7 posted on 11/25/2001 9:09:21 AM PST by Fred25

To: Fred25
Rofl..
8 posted on 11/25/2001 9:13:40 AM PST by Jhoffa_

To: Jhoffa_
The combination of the Einstein and Pythagoras discoveries:
E= m c^2= m ( a^2 + b^2)
9 posted on 11/25/2001 9:20:22 AM PST by Georgia_JimD

To: Jhoffa_
I accidentally divided by zero and my paper burst into flames.
10 posted on 11/25/2001 9:21:40 AM PST by Georgia_JimD

To: Fred25
Post office mail pasteurization. The Feds are taking bids for contracts...
11 posted on 11/25/2001 9:24:27 AM PST by Georgia_JimD

To: Jhoffa_
My question is: How is the total number of PU's calculated over a production run where the times and temperatures vary?

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.)

12 posted on 11/25/2001 9:31:23 AM PST by savedbygrace

To: Georgia_JimD; savedbygrace
Thank you for your assistance in this matter. Actually, I have a job making milk for your local supermarket and I will apply these scientific principles immediately!

Sorry bout the paper Jim.. :(

13 posted on 11/25/2001 9:38:59 AM PST by Jhoffa_

To: Jhoffa_
Phew, that's a relief. I don't drink milk, so I'm not in danger.
14 posted on 11/25/2001 9:40:13 AM PST by savedbygrace

To: Georgia_JimD
Post office mail pasteurization. The Feds are taking bids for contracts...

I boil all my incoming letters at 212 degrees for 15 minutes.

15 posted on 11/25/2001 9:44:42 AM PST by Fred25

To: Fred25
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.

16 posted on 11/25/2001 9:46:54 AM PST by Jhoffa_

To: ChemistCat
Bump?
17 posted on 11/25/2001 10:01:45 AM PST by Jhoffa_

To: Jhoffa_
See if this site about Food Engineering helps.
18 posted on 11/25/2001 10:02:15 AM PST by Georgia_JimD

To: RLK

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?

19 posted on 11/25/2001 10:47:40 AM PST by Jhoffa_

To: Luis Gonzalez
Ping!
20 posted on 11/25/2001 11:28:24 AM PST by Jhoffa_