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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?

ANY HELP you can provide will be greatly appeaciated.

Thank You.


TOPICS: Miscellaneous; Your Opinion/Questions
KEYWORDS:

1 posted on 11/25/2001 8:38:06 AM PST by Jhoffa_
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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_
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To: Jhoffa_
E=MC2 (sorry, I couldn't resist)
3 posted on 11/25/2001 8:49:14 AM PST by AngrySpud
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To: AngrySpud
Ahhh!

A pox on thee spudman!

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

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_
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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
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To: Fred25
Rofl..
8 posted on 11/25/2001 9:13:40 AM PST by Jhoffa_
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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
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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
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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
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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
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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_
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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
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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
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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_
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To: ChemistCat
Bump?
17 posted on 11/25/2001 10:01:45 AM PST by Jhoffa_
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To: Jhoffa_
See if this site about Food Engineering helps.
18 posted on 11/25/2001 10:02:15 AM PST by Georgia_JimD
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To: RLK
Insight Please?

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

Uh?


21 posted on 11/25/2001 11:40:44 AM PST by Luis Gonzalez
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To: Luis Gonzalez
You want to know what the really amazing part of this question is?

I personally know an ex-quality manager who has no idea what the answer is.. and the Present Quality Manager has no idea either (she makes seventy grand BTW)

A large majority of their products are pasteurized and they refer to the chart to determine if the product has been pasteurized properly.

Aside from that, production would cease.. because no one can accurately calculate these PU's.

No one can calculate this themselves without the Pu chart. And it's a huge company making millions a year.

I would be willing to bet you have consumed one of their products at some point..

22 posted on 11/25/2001 12:15:40 PM PST by Jhoffa_
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To: Jhoffa_
I don't have any figures. It's going to depend upon the organism ahd would need to be deterimed experimentally.
23 posted on 11/25/2001 1:56:28 PM PST by RLK
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To: RLK
Thanks for your reply RLK.

Correct, you are targeting specific organisms..

And there is a "D" value which effectively gives you a list of organisms which die after a certain time/temperature

The Lethal Rate, is calculated from this "D" value.

Assuming the Lethal Rate to be fixed. (pick a number, 1.393 works.. very close to that of beer)

How can I calculate this?

Honestly, No one can answer this.. If you need more information I will do my very best to provide it.

24 posted on 11/25/2001 2:10:12 PM PST by Jhoffa_
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To: RLK
Ps: Does the formula in #2 mean anything to you.?

The variables are: Time, Temperature, Lethal rate (use 1.393) And the sum (sigma) of total Pu's accumulated over a given period.. (delta, a change in)

25 posted on 11/25/2001 2:16:42 PM PST by Jhoffa_
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Where LT is the lethal rate, or the ratio of time (in minutes) at 60ºC resulting in the same bacteria inactivation as 1 minute at T ºC, and D tT are the time intervals.
26 posted on 11/25/2001 2:27:42 PM PST by Jhoffa_
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To: Jhoffa_
The formula is a summation operator, but I don't know what the vales are to be cummulatively added.
27 posted on 11/25/2001 4:08:31 PM PST by RLK
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To: Georgia_JimD
Didn't find anything useful there.. (except a really great gif of a HTST pasteurizer)

And, don't sweat the paper.. Lot's of guy's look sexy with no eyebrows.. Honest!

(Have I ever lied to you?)

28 posted on 11/25/2001 5:53:03 PM PST by Jhoffa_
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To: Jhoffa_
Sorry, I haven't the foggiest. I do home canning (or used to do it, before I got so sick) and the hope in that always is to kill EVERYTHING....
29 posted on 11/26/2001 12:15:19 AM PST by ChemistCat
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To: Jhoffa_
Can you help me with the calculation part of the problem?

My microbiology work on milk products goes back to the late 1950's. Can't remember a lot of specifics. I do remember that there were a couple of different ways of pasteurizing. One [the 'flash' method] involved bringing the product up to a high temperature for a very short period [perhaps a minute]; the other involved holding the product at a somewhat lower temperature for a lengthier period of time.

As I recall a critical point was the cream line . If you got milk held too long long at too high a temperature the cream turned an interesting color and was aesthetically unappealing.

30 posted on 11/26/2001 9:36:43 AM PST by curmudgeonII
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To: Jhoffa_
Can you help me with the calculation part of the problem?

My microbiology work on milk products goes back to the late 1950's. Can't remember a lot of specifics. I do remember that there were a couple of different ways of pasteurizing. One [the 'flash' method] involved bringing the product up to a high temperature for a very short period [perhaps a minute]; the other involved holding the product at a somewhat lower temperature for a lengthier period of time.

As I recall a critical point was the cream line . If you got milk held too long long at too high a temperature the cream turned an interesting color and was aesthetically unappealing.

31 posted on 11/26/2001 9:37:05 AM PST by curmudgeonII
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To: Jhoffa_
BUMP!
32 posted on 11/27/2001 3:07:57 PM PST by Jhoffa_
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