10 replies to this topic

[Charles.C]

Dear Jean,

What kind of blast freezer are you thinking of ? The typical criteria include time to adequately freeze (eg <= -18degC core temp) specified quantities of product. Not familiar with anything between large size freezer box / Refrigerator and a small (but still large) manufacturing unit, not sure I would call the former a blast freezer ?

Rgds / Charles.C

[Bobby]

"I would like to know if any catering or retail units are using a blast freezer to freeze cooked items so that it can be stored in a freezer with a one month shelf life and whether this is a safe operation."
We have so many hotels in Dubai that use blast chillers to cool food down quickly ( from 60 Deg C to less than 5 Deg c) and the time depends on the type of food and size/shape of container and ofcourse the efficiency of the chiller.
In a blst freezer, you can get the temperature to -18 very quickly but why do you need it in retail operations?
The freezing process and subsequent storage at that temperature will not affect safety. Cooking destroys vegitative cells, but spores survive unless the food is cooked to very high temperatures. During blast freezing, spores cannot germinate but they will continue to survive.

If the food is temperature abused later, spores can germinate and multiply. There are a lot of cooked and then frozen food products available in the market with more than an year's shelflife.

"Can chilled products like chilled products or live seafoods (like lobsters)be frozen using a blast freezer?Is this method acceptable in a catering/ retail operation to increase the shelf life."

If your raw material is good, then there is nothing to worry about. Fishes are normally blast frozen due to quality issues ( reduces tissue damage).

"Is there any reference for blast freezing of raw and cooked products in-house especially in a catering operation and not in a manufacturing or seafoods unit."

You can find a lot of references for blast chilling ( codex guidelines and food code).

Bobby Krishna
Food Inspector
Dubai Municipality

[Charles.C]

Dear Jean,

From a freezing-manufacturing background (but not sauces) so not sure how valid for you but the frequent problem for storage of frozen products is freezer burn (which you know already I'm sure). This applies to block / IQF whatever and will vary depending on the item and packaging protection both during the freezing process and after. A typical target for plate freezers is ca. 2hrs for a 16Lb unit (seafood) to achieve -18degC however I'm sure the (air blast?) times you give shd be ok. Normally for 1month storage, I would guess basic quality shd not be problem except if the packaging/temp control is inadequate. For seafood, standard air blast freezers work although you can get better quality results using CO2 / N2 freezers but at a cost and maybe not available yr quantity scale.

No experience chilling but presumably L.mono.... could be a problem some items (depending on cooking) in addition to spores ?

Rgds / Charles.C

[Bobby]

Jean,


we use the blast freezer for freezing different sauces like demiglaze, mushroom sauce, tomato sauces, pepper sauces, crane berries sauces etc....

The food items ( Sauces) you are freezing are absolutely safe because there are so many hurdles for the pathogen to overcome: Temperature, Low pH and Low water activity.
There are hotels in Dubai that follow Cook - Blast chill - Freeze ( In walk in freezer) step for such sauces. I know that it is not easy to make sauces every other day.


"I agree with you spores survive freezing, but I would consider spores as a significant hazard in blast chilling."

Spores survive freezing and they germinate only when you temperature abuse the food.
In a blast frozen product, this happens only if the food is stored at hazardous temperature for a substantially high time during thawing.


"I would say if the foods are stored in correct temperatures with minimum fluctuations and used within the set shelf life there will be low chances for the microbiological risks including effective cleaning and correct storage rules being followed."


In the case of blast frozen food, there wont be any pathogen growth until the food is thawed ( Lowest temperature at which listeria can grow is around -1.4 Deg C and it is not a concern in the foods that you have mentioned).

Bobby Krishna
Food Inspector
Dubai

[Jean]

Dear Bobby,

Thanks for your reply.

What do you suggest regarding blast freezing of soups, stocks and curries, is it being practiced in hotels?

Thawing is very important as you mentioned and we have controlled thawing process as we use thawing cabinets and chillers.

BR,

J

[Bobby]

Jean,
We do blast chill the sauces and then freeze it.
The sauces are cooled and then portioned before freezing. This gives better portion control and reduces waste.
It is not easy taking small portions from a frozen block if you go the other way.
Some of the sauces with low pH can be cooled at room temperature ( this will save you some power as well).

What do you do? Do you pack sauces before blast freezing?
I know that it is not easy to pack the sauces manually when it is hot.

If you look at the regulations in US, shelf life for PHF stored chilled is one week. if you freeze a product during this period, the number of days the product remains frozen is not counted.
In short, the shelf life clock starts ticking when the food is prepared and refrigerated. The clock stops ticking when you freeze it. it resumes ticking when the food reaches refrigeration temperature again.

Regards,

Bobby Krishna

[Jean]

Dear Bobby,

Thanks a lot for your info. We portion in small trays / containers as required and then blast freeze. This will be thawed by placing the trays in chiller one day in advance and then used within 3-4 days.

The bulk prepared sauces will be transferred to containers when the temperatures are around 80oC - 85oC and then blast freezed. I was told by the head cook that if the stocks , curries or sauces are blast chilled and then placing in freezer for freezing, then it results in more and larger ice crystal formation and moreover there are chances for the separation (curdling) of the particles which result in emulsions and may not be that good- quality wise...

That's how we practice.


J

[Bobby]

You are right, large crystals do form when slow freezing is done.
This is why I said it is better to portion and then freeze. Small pouches freeze much more faster.

[charu13]

Great piece of information.I found  this discussion very helpful.

 

 

 

 

 

Regards,

Charu Tyagi