Why Freezer temperature is to be below -18 degree C

[Sinu]

Almost all the bacteria stop the multiplication when the temperature reaches to -10 degree C or below then why it is stipulated that the freezer temperature has to be -18 or below

[Pete Snyder]

Sinu is absolutely right. The lowest growing pathogens are Listeria
monocytogenes, Aeromonas hydrophila, and Yersinia enterocolitcia at -1.5
C. -18C is a quality control temperature.

Pete
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[Andres Despi]

Hi All,

 

Psychrophiles or cryophiles (adj. cryophilic) are extremophilic organisms that are capable of growth and reproduction in cold temperatures, ranging from −15°C to +10°C. Temperatures as low as −15°C are found in pockets of very salty water (brine) surrounded by sea ice. They are present in alpine and arctic soils, high-latitude and deep ocean waters, polar ice, glaciers, and snowfields. Examples are Arthrobacter sp., Psychrobacter sp. and members of the genera Halomonas, Pseudomonas, Hyphomonas and Sphingomonas. (This was taken from Wikipedia modified last April 24 2012)

But any study/reference defying these facts, it is highly appreciated.

Regards,

Andres

 

 

On Wed, Jun 20, 2012 at 5:11 PM, Pete Snyder <osn...@hi-tm.com> wrote:

Sinu is absolutely right.  The lowest growing pathogens are Listeria monocytogenes, Aeromonas hydrophila, and Yersinia enterocolitcia at -1.5 C.  -18C is a quality control temperature.

Pete
----------------------

Sinu wrote:

Almost all the bacteria stop the multiplication when the temperature reaches to -10 degree C or below then why it is stipulated that the freezer temperature has to be -18 or below
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[Bobby Krishna]

Andres,

Are these bacteria the normal microflora on food? 

Bacteria are the best survivors. They have adapted to almost all conditions in the world. There are thermodurics and hyperthermiphiles that can survive very high temperatures. Does that mean that all foods have to be cooked to 500 Deg C?

Can you please avoid arguments for the sake of arguing. 

Regards

Bobby

Bobby krishna

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[Bobby Krishna]

Pete,
It was perhaps easy to say 0 Deg F as a limit. I think most parts of the food gets completely solidified at that temperature.

At -10, core region will still be liquid keeping the enzymes active. Quality deterioration and not safety is the issue I guess.

Bobby krishna
Sent from my iPhone. Please ignore the spell errors

[sunu.r...@gmail.com]

Bobby,

I agree with you - it is to arrest the enzyme activity. - 18 Deg C or 0 Deg F all proteolytic enzymes in the cells are inactive and it helps to increase shelf life. It is a quality control aspect than safety.

Regards
Sunu R S
Empower your Business with BlackBerry® and Mobile Solutions from Etisalat

[Bobby Krishna]

Andres,

// For some thermophiles bacteria, if we need to heat into 500 Deg C? If its practical then it is better but if its not then lets try some alternatives. //

What are you trying to achieve by cooking - kill all that is alive?

Food safety is not about practicality, but all about necessity. 

When deciding temperature for cooking or chilling or freezing, you look at what is necessary to preserve the food and at the same time provide the nutrients we require at an affordable price. Not one without the other.

If you are here to discuss basic microbiology, lets have a private chat.

Bobby

On Thu, Jun 21, 2012 at 5:27 PM, Andres Despi <andy42...@gmail.com> wrote:

Yes,

 

Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many natural and artificial environments. It uses a wide range of organic material for food; in animals, the versatility enables the organism to infect damaged tissues or those with reduced immunity.

 

My point here is that the scientist study the presence of bacteria in places below freezing point. The fact that they survive there, they have also the capacity to strive in our freezer.

 

For some thermophiles bacteria, if we need to heat into 500 Deg C? If its practical then it is better but if its not then lets try some alternatives.

 

Regards,

Andres

--

Bobby Krishna

Interested in food safety? 
 

[Andres Despi]

Yes,

 

Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many natural and artificial environments. It uses a wide range of organic material for food; in animals, the versatility enables the organism to infect damaged tissues or those with reduced immunity.

 

My point here is that the scientist study the presence of bacteria in places below freezing point. The fact that they survive there, they have also the capacity to strive in our freezer.

 

For some thermophiles bacteria, if we need to heat into 500 Deg C? If its practical then it is better but if its not then lets try some alternatives.

 

Regards,

Andres

 

 

On Thu, Jun 21, 2012 at 5:03 PM, Bobby Krishna <bobbyk...@gmail.com> wrote:

[HARI]

This classification that is extremophiles and mesophiles has been used generally depending on their survival chances in exteme or moderate natural environment. Wikipedia itself states that "The category name extremophiles is unfortunate as it calls for subjective judgements of two issues - firstly, the degree of deviation from 'normal' justifying the use of 'extreme', and secondly, whether the organism prefers the environment or merely tolerates it".

   Appropriate classification as far survival temperature is concerned is thermophiles , mesophiles psychrotrophs and psychrophiles. As far as my knowledge is they are classified as per the table given below.

Classification	Temperature Range (°C)	Optimum Growth Temperature (°C)
Psychrophile	-10 to 20	10
Psychrotroph	5 to 30	25
Mesophile	10 to 45	37
Thermophile	40 to 75	55

 

With Best Regards
Harish

---

From: Andres Despi <andy42...@gmail.com>

To: Pete Snyder <osn...@hi-tm.com>
Cc: Sinu <sinus...@gmail.com>; foodsaf...@googlegroups.com

Sent: Thursday, June 21, 2012 12:15 PM

Subject: Re: {Food Safety Dubai} Why Freezer temperature is to be below -18 degree C

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[bigal]

Gentlemen,

Many of you have drifted off the point.

I am writing this message with a Marks and Spencers frozen pizza in front of me.

It has a "best before date' of September 2012.

That is only valid provided that it is stored at minus 18C.

You can debate the microbiology as much as you like but most food has a validity period (difference between production and expiry date) and that validity relates specifically to the storage temperature. If it is not stored at the requisite storage temperature, then it's shelf life will be affected. Doesn't matter whether it's frozen, chilled or in a can.

It's a legal requirement and it's a quality control issue.

Allan Hough.

Higher Colleges of Technology.

On Wednesday, June 20, 2012 12:57:36 PM UTC+4, Sinu wrote:

[Sinu]

But when we focus on food poisoning bacteria their temp rang will be around 15 c to the maximum 50 c except the clostridum sp. and listeria,

 there are extremely tolerant bacteria present in deep sea vents and in volcanic areas, 

but then also why this -18C we are considering as the freezer temp,

I agree with the fact that enzyme activity get stop that increase the shelf life....

for an example consider the freezer what we are talking about is in a fast food restaurant like KFC or B.K so the product may last up to the maximum 10 to 20 days so in such situation this -18c is so necessary...

On Wednesday, June 20, 2012 12:57:36 PM UTC+4, Sinu wrote:

[Sinu]

The OHIO State University had published an article regarding freezer storage (HYG-5402-94-R10) states that at 0 degree F we can maintain their quality, freshness and nutritional value, when an enymatic activity stops in the product all these can be achieved and the shelf life also can be increased.so i agreee with Bobby's statement.  

On Wednesday, June 20, 2012 12:57:36 PM UTC+4, Sinu wrote:

[Douglas Allan Hough]

Sinu,

0 degrees Fahrenheit = minus 17.77 degrees Celsius. (i.e. -18 C)

Allan.

Higher Colleges of Technology

--

[Pete Snyder]

Sinu,

Actually many commercial freezer target -30C or lower for long term 1
year or more frozen storage of food such icecream and food like fish
with unsaturated fats. At -30 and and -40C there are still slow
changes. One important variable is temperature fluctuations. There are
still pockets of salt liquids and the little pockets freeze and thaw
cycle making ice crystals that freeze and thaw and effect the quality of
food. Commercial freezers cycle less than 1 C. in order to minimize/slow
change. Freezers in kitchens are not built for long term storage, even
at -18C.

Pete Snyder

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[Bobby Krishna]

pete
-60 C is used for transporting nitrogen freezed fish. It stops almost all internal changes.

[Pete Snyder]

Bobby, That is an excellent example of the use of very low temperatures.

Pete
--------------------

Bobby Krishna wrote:
> pete
> -60 C is used for transporting nitrogen freezed fish. It stops almost
> all internal changes.
>
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[Loraine Hughes]

I wanted to add points on the practical experience I had within the frozen cooked meal industry.
 
Once frozen (storage at -18C to -22C), the microbiological quality of the ready-to-heat food product / meal was fairly stable although there was a decimation in coliform counts (if present) directly related to the time and temperature the product was stored at.
 
There was an organoleptic impact over storage time - mainly colour (brightness and intensity due to oxidation) and texture (as mentioned by Pete due to storage temp fluctuations impact). Generally fish, certain vegetable-based and potato based meals were limited to 75% of the shelf-life we afforded other products. Besides this, of course, there was a difference between a product at start of shelf-life and end of shelf life - e.g.: rice grains were not as moist. The shelf-life was set in relation to organolepsis ensuring that there was a minimal discernable difference on the reheated defrosted food product / meal at consumption within its shelf life.
 
Additional Food for thought.....
We all agree that in food production food safety is non-negotiable. The shelf-life of products are set keeping variables such as customer requirements including quality expectations and affordability, the process capability, costs (particularly those for energy to maintain the required storage temperature),  sustainability, etc in mind. Freezing foods and maintaining them at frozen temperatures is costly. Most large companies are looking at alternate preservation technologies to move to ambient shelf-stable products... imagine the cost savings on warehousing and logistics alone.
We have an interesting time to look forward to....
 
Loraine

 

> Date: Fri, 22 Jun 2012 10:38:10 -0500
> From: osn...@hi-tm.com
> To: sinus...@gmail.com
> CC: foodsaf...@googlegroups.com
> Subject: Re: {Food Safety Dubai} Re: Why Freezer temperature is to be below -18 degree C