Blast freezer related issues ~~

[spiderman]

Basically (as I am aware of) there are three key issues relating to air Quality in refrigeration:

1. Air Cleanliness – Air has to be clean so that the foodstuffs are not contaminated with oil, dust etc. so Air filters should be used. but where in the blast freezer system?

2. Humidity – Relative Humidity (dont know much about this)

3. Bacteria – a certain temperature that has to be reached to prevent bacteria from growing (e.g. for beef, fish)

ps. its related to UK. or would legislations for this be standardised internationally.

thanks for your kind help.

[lana]

Hi spiderman,



1. Air Cleanliness – Air has to be clean so that the foodstuffs are not contaminated with oil, dust etc. so Air filters should be used. but where in the blast freezer system?


There is no air filter in blast freezer. Air filters are only used for air conditioning. As you know in refrigeration evaporators, axial fans are used which can not tolerate pressure drop.


2. Humidity – Relative Humidity (dont know much about this)


Required relative humidity in the room dictates the selection of the evaporator. If evaporator Delta T (tr-te) is around 5 or 6°C then high relative humidity can be achieved. if evaporator delta T is around 9 or 10°C then lower relative humidity is obtained in the room.


3. Bacteria – a certain temperature that has to be reached to prevent bacteria from growing (e.g. for beef, fish)


If air or the product in the cold room is already contaminated , there is nothing that cooling system can do about it.
Blast freezers usually are designed for -30 to -40°C room temperature.

Anyway this is what I know.

Hope this helps.
Cheers:)

[environtech]

Hi spiderman,

There is no air filter in blast freezer. Air filters are only used for air conditioning. As you know in refrigeration evaporators, axial fans are used which can not tolerate pressure drop.

Required relative humidity in the room dictates the selection of the evaporator. If evaporator Delta T (tr-te) is around 5 or 6°C then high relative humidity can be achieved. if evaporator delta T is around 9 or 10°C then lower relative humidity is obtained in the room.

If air or the product in the cold room is already contaminated , there is nothing that cooling system can do about it.
Blast freezers usually are designed for -30 to -40°C room temperature.

Anyway this is what I know.

Hope this helps.
Cheers:)

Hi Spiderman / Lana,

GREETINGS FROM SRILANKA

Lana's reply to Spiderman is in line with current practice. As far as I'm aware there is no ( outside )air circulation in blast freezing - so idea of contamination by external air is ruled out.

Re: temp range for blast freezing I have come across - 60 C, in the sea food export industry here.

Environtech

[environtech]

Hi Spiderman,
GREETINGS FROM SRI LANKA

I have already posted comments on Lana's reply to you.

(A) Re: Relative Humidity - The air around us is a mixture of several gasses, moisture, etc.

The amount of moisture the air contains is fixed by nature depending on the atmospheric pressure / temperature, and is an extremely important factor in the design of AC & REF systems.

Relative humidity ( expressed as a percentage ) is the ratio of the actual moisture content of the air to the moisture the air can accomodate under any given atmospheric pressure / temperature.

Mathematically RH = actual moisture in air (1) / amount of moisture the air can contain (2)

(1) is measured by an instrument called the Psychrometer and (2) is taken from already prepared charts.

(2) Different bacteria thrive in different temp / humidty conditions.
Blast freezer temperatures and time duration of blast depends on product nature / dimensions, etc, as the idea is to blast core of product to storage temperature in required time.

I hope the explanation is clear.

Best Wishes

Environtech


Hi spiderman,

There is no air filter in blast freezer. Air filters are only used for air conditioning. As you know in refrigeration evaporators, axial fans are used which can not tolerate pressure drop.

Required relative humidity in the room dictates the selection of the evaporator. If evaporator Delta T (tr-te) is around 5 or 6°C then high relative humidity can be achieved. if evaporator delta T is around 9 or 10°C then lower relative humidity is obtained in the room.

If air or the product in the cold room is already contaminated , there is nothing that cooling system can do about it.
Blast freezers usually are designed for -30 to -40°C room temperature.

Anyway this is what I know.

Hope this helps.
Cheers:)

Hi Spiderman / Lana,

GREETINGS FROM SRILANKA

Lana's reply to Spiderman is in line with current practice. As far as I'm aware there is no ( outside )air circulation in blast freezing - so idea of contamination by external air is ruled out.

Re: temp range for blast freezing I have come across - 60 C, in the sea food export industry here.

Environtech

[spiderman]

thanks for your reply Environtech...im more clear on this now.

where do u know i can find out info on (2)...from food industry board?

[Peter_1]

What product do you want to freeze, what's the capacity and what's the entering temperature?
These are the first basic question.