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Freezing in Freezer Critical Limits

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Sparkle27

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Posted 19 May 2022 - 07:42 AM

Hi,

We are a company that produced RTH cooked meals. The overall process are "cook - blast chill - pack - blast freeze". I am in the midst of writing the critical limits for blast freezing. In a scenario, when a blast freezer is not working, what will be alternative critical limits in the freezer? 

 

Eg. in a chiller it will be 60 deg C to 10 deg C in 4 hours

 

what will be the critical limits in a walk in freezer/reach in freezer: 21 degC to -18 deg C in ____ hours(if any)

 

Thank you.



Evans X.

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Posted 19 May 2022 - 08:42 AM

Greetings Sparkle,

 

To my knowledge there is no specific time limit, other than what most state "As fast as possible". However in practice what you care more is how long it takes to get under the lower temperature limit of the danger zone (microbial growth optimal temperatures), which is somewhere under 6oC or 0oC if you want to be stricter or afraid of eg Listeria (?), so if you reach this within 4 hours (again an average from bibliography and legislation/guidlines of some countries), then the rest of the way is a question if the longer time it takes to reach -18oC has any imact on the quality of the product.

Using blast chiller as you mentioned though and then putting them in a freezer shouldn't cause any safety problems. Furthermore blast freezing is of more importance for RTE foods that don't get any treatment like cooking.

You could always back this up with a microbial analysis on the packed food before and after freezer, to see if you have any microbial growth.

 

Regards!



Scotty_SQF

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Posted 19 May 2022 - 01:10 PM

You could do your own test to determine the limits.  It is what I have done in the past.  Take an expired or non-useable case of the product out of the freezer and place it in room.  Take the temperature inside the case at certain time intervals, say every 30 minutes.  Document the temperature and see how long it takes for the product to reach it's critical limit.  Document the results of your test then you can use that test as a basis to say that in such and such hours of the freezer not working you would reach a critical limit.  Of course the time would be cushioned as if the freezer stopped working it doesn't instantly warm up so you would have extra time, but you'd still have data to show once taking out of the freezer and being a standard room temperature it took this long to reach the critical limit.  Hope this helps and makes sense.



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Posted 19 May 2022 - 02:25 PM

my issue with this is the laws of thermodynamics

 

Without a blast freezer, in all likelihood (depending on how your cartons are packed), the centre cartons/retail packs may actually RISE in temperature before they ever start to freeze

 

So you need to also have a back up plan, to lay units out in single layers to freezer PRIOR to packaging, and some countries will not allow you to do that if they aren't coverer to protect the food from contamination

 

Need quite a bit more information here before you formulate your deviation procedures

 

Blast freezers work by removing the heat from the surface of the food causing the internal heat to move out as the material tries to make the temperature uniform (thermodynamics). The velocity of the air plus the extreme wind chill created are why blast freezers work so efficiently without any appreciable rise in temperature

 

Traditional freezers work in the opposite way--the stagnant ambient air slowly forces the warm material into the centre and takes significantly longer to achieve frozen in the core

 

You run the risk of your product being in the danger zone for a considerable amount of time


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Charles.C

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Posted 21 May 2022 - 08:07 AM

Hi,

We are a company that produced RTH cooked meals. The overall process are "cook - blast chill - pack - blast freeze". I am in the midst of writing the critical limits for blast freezing. In a scenario, when a blast freezer is not working, what will be alternative critical limits in the freezer? 

 

Eg. in a chiller it will be 60 deg C to 10 deg C in 4 hours

 

what will be the critical limits in a walk in freezer/reach in freezer: 21 degC to -18 deg C in ____ hours(if any)

 

Thank you.

Hi Sparkle,

 

IMEX this seems an atypical  process.

 

Why have 2 stages (a) in a blast chiller then (b) in a blast freezer ?

 

Normally IMEX frozen end product is a one-step freezing procedure, ie no need for  chilling.(Packing is either pre- or post- freezing).

 

I deduce final product is RTE / frozen.

 

What is Product ?

 

Unclear if product is IQF or Glazed Block or ?

 

Unclear if batch or continuous freezer. Typical freezing times may be substantiallly different.

 

Minimum freezing time will relate to size, eg thickness of product.

 

Please clarify yr process.

 

Regardless, IM(seafood)EX of RTE / non-overloaded freezer of retail product dimensions, this step is typically not a CCP. (I have seen a few, IMO, debatable haccp exceptions where input temperature was a critical limit).

 

PS - never heard of a walk-in freezer, only a walk-in storage unit.


Kind Regards,

 

Charles.C


Scampi

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Posted 24 May 2022 - 04:06 PM

Charles---walk in freezer is likely what you're calling a walk in storage unit

 

I.e. very large freezer with a door large enough to allow a full pallet through  usually used as freezer storage

 

That's what we call them in Canada as well


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Charles.C

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Posted 24 May 2022 - 07:54 PM

Charles---walk in freezer is likely what you're calling a walk in storage unit

 

I.e. very large freezer with a door large enough to allow a full pallet through  usually used as freezer storage

 

That's what we call them in Canada as well

If so, IMO, the answer to OP's query is simply "indeterminate". The purpose is storage, not freezing. Reminiscent of ye olden days.


Kind Regards,

 

Charles.C




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