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monkey spanners
16-12-2014, 09:06 PM
Got a customer with a now static lorry body that they are using as a meat cold room, beef mainly, they are having a problem with mold growing on the meat, it looks like a fur coat!

What would cause this?

We have replaced the original thermoking evap with a suitably sized one from Searle and the system has been running since about a year ago. I am not sure how long the mold issue has been going on.

hookster
16-12-2014, 09:16 PM
What is your holding temperature? How far are you varying above and below set points?
You say you have replaced the evaporator with a suitably sized one? can you give more detail i.e. what is your design TD

You most probably have a high humidity condition in the converted trailer or on opening the door you are exposing the meat to large temperature fluctuations and exposing it to condensation.

Are you stopping evap fans during off cooling cycle?

The Viking
16-12-2014, 09:30 PM
3 things really;
- Temperature
- Humidity
- Age

The next thing to bear in mind is obviously the design vs usage, this lorry body's original design were most likely never intended to bring room tempered meat down to refrigerated temperature only to hold cold meat at temperature.

:cool:

monkey spanners
16-12-2014, 09:49 PM
It started off just being for a few turkeys last year...

It was originally a freezer on R404A, we changed it to R134a when the new evaporator was fitted which is matched to the compressor, though i think it is probably a bit over sized. Fans are on all the time except defrost.

cadwaladr
16-12-2014, 11:12 PM
Has it got its own condensing unit? or are you using the thermoking compressor and condensor

cadwaladr
16-12-2014, 11:14 PM
And what temperature are the carcasses when they are put in the box

monkey spanners
16-12-2014, 11:26 PM
Its still running the thermoking unit, i have fitted a three phase condenser fan in place of the 24v dc one.

Not sure on the carcasses though i think they are chilled from the abattoir, we have to check.

cadwaladr
16-12-2014, 11:39 PM
sounds like a small truck body,what type of compressor is it ,

cadwaladr
16-12-2014, 11:42 PM
and what have you done to get rid of the hot gas defrost which was original to the unit?

monkey spanners
17-12-2014, 12:26 AM
Think its a Frascold 1.5hp, the truck was a 7.5t. The hot gas has been blanked off, the new evap has electric defrost, we are running a Danfoss Optyma control.

cadwaladr
17-12-2014, 12:52 AM
quite a small unit that i think it must be a v500 ,beef carcasses are quite a heat load how many are in the box,airflow is critical i presume they are on meatrails by putting it on 134a its going to be down on duty what model searle evap is it ?

mikeref
17-12-2014, 09:54 AM
"Viking" on post #3 narrowed it down. Short run cycles will keep humidity too high. Long run cycles will dry/ burn the Meat, though it doesn't seem to be just one problem here. Adequate air circulation? +2 to +4 C temperature cycle? Meat was delivered by refrigerated transport?

In isolated areas, we have Farm Butchers contracted to kill and Quarter the meat. Hang it in a mobile coldroom for a day or two before sectioning it. Never had a problem with Mould growth.

RANGER1
17-12-2014, 10:31 AM
Is there a lot of sudden unexpended deaths in the area?
What do they do with the mouldy meat? Throw it away of course!

We have not seen any temps given, which would help, but I think a thorough decontamination of the van with suitable cleaner would be a good start & on a regular basis.
Thats what you would do in your fridge at home isn't it!

mikeref
17-12-2014, 12:27 PM
To be honest, anything with Mould growing on it has to have access to a favourable temperature and water content.
Monkey Spanners: Your customer isn't giving you the full picture.

Ranger 1....We are several thousand Miles apart however....Best wishes to you and yours over the Xmas season.

MikeHolm
17-12-2014, 12:49 PM
As well as looking at the frig conditions, this is an old box, right? Is it sealed properly? There could be lots of small holes letting air in where you don't want it.

cadwaladr
17-12-2014, 03:08 PM
Some years ago beef carcasses were shipped all around Europe in refrigerated trucks,think they called it intervention beef and I never saw issues like mould? But the units had ducting chutes fitted to provide adequate air circulation think you have a serious issue with that fridge plant,keeping Turkey's cool is one thing ,sides of beef is as I said before higher heat load.

chemi-cool
17-12-2014, 05:39 PM
mold is bacteria that needs heat to grow.

Its the defrost heaters that bother me, why do you need to use heating to defrost? Air defrost is not enough?

Where is the evaporator situated? front [above the door]/ or at the back? does the fans stop when the door opens?

Is there some sort of temp chart?

monkey spanners
17-12-2014, 11:35 PM
Am back there tomorrow, will have a better look at it. It needs the defrost as they keep the room very cool.

Thanks for the replies! :o

B G Scott
18-12-2014, 08:52 PM
Very strange, humidity would seem to be the area to check, although high humidtity would usually reault in slime forming the carcass.
Check the TD this is important to reduce weight loss, but the problem you have seems to be introduced from an external source, what was the truck used for prior to this application?

monkey spanners
18-12-2014, 09:11 PM
It was a meat delivery freezer before, it has the meat rails already in it. Didn't make it there today, had a milk tank that sprung a leak to go to instead!

monkey spanners
10-03-2015, 01:09 PM
Just an update, I was told by one of the wholesalers of a similar problem they were having with a meat room installed underground, seems there is not enough run time to dry the air out as the room is pretty much at temperature most the time anyway, so cold and damp giving rise to mold etc.
On their advice we adjusted the defrost setting for more frequent defrosts, more to put some heat back in the room so the cooling would actually run than to clear the coil, and put a wider differential so it would run longer when it did run. So far there has been no more problems with mold, though i realise the weather has also been a bit warmer.
Some other advise i was given was that a uv light in the room would be helpful too, though i have not needed to try one yet to see.

chemi-cool
10-03-2015, 04:18 PM
Many, many years ago I have built a large cold storage for flowers bulbs and the requirements was 2c and 30% humidity,
Evaporator was at -5 evaporation and I have installed 3 heating elements in front of fans. These heating elements were controlled via humidistat so by heating the air, they have forced the compressors to run and the evaporator dried the air pretty good.
Defrost was hot gas at 4 hours intervals.
There was about 15 tons per room and it took about 3 days to reach 40% humidity.

its pretty much like your problem.

Magoo
11-03-2015, 03:48 AM
Hi MS.
problem is too high humidity / RH, mould is bacteria and blossoms as hairy fur still active at medium temperatures, too late the meat is screwed. Despite the holding temperature. Short term high humid is good as ageing and conditioning for tender meat, but short periods. Basically rotting the meat quickly to tenderise it. Check super markets, if fresh does not sell they marinate it or sell as stew half cooked.
Back ground, I worked for a period over here for Meat Research .