Calculate Fo Value for UHT Process

Hi All,
I am also not clear about how to calculate the Fo Value for UHT process.
Example: my product is Ready To Drink Tea
pH : less than 3.5
UHT Condition: 116oC & holding time : 20sec.
How i calculate the Fo value for this process. I don't have info about Heating step (embient temp. to 116) and Cooling Step (116 oC to 88oC) for filling. Do theses steps contribute to Fo Value ?

Thanks

Dear Tran Lam Thanh,

I doubt that 116degC is classified as UHT.?

As you say, you are missing some data for a complete analysis for F0.

Data points below 100degC can usually be neglected for the times involved in this case.

One approximation is to neglect the heating / cooling periods. The error will be small if times are rapid. Result will be a minimum value for F0.

Formula for uniform temperature period (ie 20secs) is –

F0 = (t/60) x 10 ^ [(T-121.1)/z]

Symbols
F0 is the number of minutes of equivalent sterilisation at 121.11°C.
^ = (to the power)
t = sterilisation time in seconds at T °C
T = sterilisation temperature in °C
121.1degC = sterilisation reference temperature
z = a value expressing the increase in temperature to obtain the same lethal effect in the 1/10 of time. The value varies with the origin of the spores (10 – 10.8°C) and can generally be set as 10°C. (ex milk handbook)
(If the formula is expressed in °F, the reference temperature is 250°F and the z value normally 18°F.)

The result for t=20sec is F0 = 0.103 min (approx).

You can also try the data out in an on-line calculator at –

http://www.dairyscie...info/uht123.asp
(the answer will probably be approx 0.1)

Rgds / Charles.C

PS Pls revert if your answer different, maybe my error.

Many Thanks Charles.C
Do you have any standard about Fo Value for each kind of product (pH<3.5, pH>4.5,...) ?

Dear Tran Lam Thanh,dear all, the process whose sterilizing temperature is lower than 130oc,it is impractical  to calculate the sterilizing intensity with the reference temperature at 121oc,i suggest the reference temperature at 95oc, then the formula is  (t/60) x 10 ^ [(T-95)/z]

Dear Tran Lam Thanh,dear all, the process whose sterilizing temperature is lower than 130oc,it is impractical  to calculate the sterilizing intensity with the reference temperature at 121oc,i suggest the reference temperature at 95oc, then the formula is  (t/60) x 10 ^ [(T-95)/z]

Dear zhou,

No problem but it will then be necessary to designate the result as something other than F0.? And rewrite all the English language canning texts ?. :smile:

F_zh perhaps ?

Rgds / Charles.C

Dear zhou,

 

No problem but it will then be necessary to designate the result as something other than F0.? And rewrite all the English language canning texts ?. :smile:

F_zh perhaps ?

 

Rgds / Charles.C

deaar charles.c, it should be rewrite the result other than F0, and the F0 is only the sterilizing intensity at 121.1oc, also the sterilizing intensity can be write as F95 or F65, do you remember the meaning of the PU, or the P*, or the B*? otherwise should it all be write as F0? it is impractical!

Dear zhou,

I'm not sure I understand yr comment.

I have no particular objection to using any of quantities like F0, B*, C* as appropriate. Or a lethal effect referred to any other convenient temperature. My comment was only regarding the conventional use of 121.1 degC for F0 and the latter's typical use in canning  theory.

If you are disagreeing with the common usage of F0 in canning texts, i guess it's just a matter of opinion. :smile:

Rgds / Charles.C

Hi All,
I am also not clear about how to calculate the Fo Value for UHT process.
Example: my product is Ready To Drink Tea
pH : less than 3.5
UHT Condition: 116oC & holding time : 20sec.
How i calculate the Fo value for this process. I don't have info about Heating step (embient temp. to 116) and Cooling Step (116 oC to 88oC) for filling. Do theses steps contribute to Fo Value ?

Thanks