Flash Pasteurization Time And PU Advice Needed.

[Stephen Schuurman]

We use a flash pasteurizer for our finished cider before sending into our bright tanks for carbonation. We currently do not use a PU meter as the engineer who installed the machinery and did tests told me that the correct rate was 180 degrees Fahrenheit for 8 seconds.

I have been running the juice through at this rate and the temperature of the juice coming from the pasteurizer is around 70 degrees F.

My questions are is this the correct rate? I have been trying to find an easy way to convert time and temperature into PU without success. Also would a PU meter purchase be a necessity so I know that I am pasteurizing using the correct parameters?

Many thanks for any help.

[luke...@gmail.com]

Pasteurization units can be calculated according to the formula available here:

https://sizes.com/units/pasteurization_unit.htm

A pasteurization computer would monitor the temperature and time and calculate this formula continually so show the accumulated PUs.

Cheers,

Luke

[Claude Jolicoeur]

Le lundi 5 février 2018 10:55:19 UTC-5, lukecyca a écrit :

A pasteurization computer would monitor the temperature and time and calculate this formula continually so show the accumulated PUs.

These are fine for bath pasteurization.

However in a flash pasteurization, I am not too sure that this would work...  The principle is different as the cider is flowing inside an heat exchanger.
To calculate the actual PUs, you'd have to have many temperature sensors inside the heat exchanger, and work with the flow in order to determine how much time the cider has been at such a temperature.

I suppose the engineer who installed the system must have had tables for the particular exchanger he installed, from which he was able to determine how much PUs are given to the cider given a certain flow and a certain heat input. There is in my opinion no way we can confirm that the rates and flows he determined are correct whithout having all the relevant documentation.
Note also that in a flash pasteurizer, if you increase the flow, you decrease the PUs as the cider flows faster, and remains at temperature for less time. And the opposite if you decrease the flow.

Claude

[Stephen Schuurman]

I am unclear how he dialed the system in. I can control the flow rate easily which is now down to 16 gpm from it's original 20gpm. I suppose the only way I can be 100% sure is if I get someone from the manufacturers to visit our site and advise. However, as it is an older unit this may prove difficult. I can also turn off the cooling water and measure the temperature a sample of juice on its way out to make sure the temperature is around 180 degrees F and time the juice from when it first goes in until it emerges.

I need to get this running to the exact specs asap

[Wes Cherry]

You could approach this from the other end and try different heat and flow rates and send samples to a lab for microbial analysis. Include a pre-pasteurization sample as a control.

With the definite chance of downstream contamination in the bright tank and bottler, regular monitoring of your bottled cider would be a good idea as well.

-'//es Cherry

Dragon's Head Cider

Vashon Island, Wa US

www.dragonsheadcider.com

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[Stephen Schuurman]

Wes

Thank you for the answer. I have indeed sent samples to our local lab and they have also taken swabs from various places in our facility. Likewise I have also had our canned cider analysed and it is a very small yet random spotting of contamination. 

I will experiment with sending away samples of different flow rates as you suggest until I hear back from the pasteurizer manufacturer.

Many Thanks

On Sunday, February 4, 2018 at 3:12:11 PM UTC-5, Stephen Schuurman wrote: