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Humidity and mould in chill warehouse unit

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Posted 17 April 2018 - 09:25 PM

Hello All

I’m looking into a problem at the moment regarding mould spots appearing on butter blocks in a chill warehouse. The spots are found after typically 3-6 weeks on random blocks when they are being deboxed and required for production. For those who don’t deal with butter, the blocks are normally 25kg, about 50lbs, wrapped in a plastic liner and in a cardboard box which is taped. Attached is an example with the block showing so you can see it’s not 100% sealed off from the environment. 77fc774c2ed61235f5af12d7de0d91f0.jpg

It’s a very small percentage, a few blocks every few weeks, but it happens to blocks coming from several different suppliers via different warehouses so I’m suspect of the warehouse unit as it appears to be the only common point. My concern is that it will suddenly become a bigger issue so better to deal with it now.

We’ve looked at humidity and temperature within the store. Temp is good consistently between +1 and +5 degrees C. Humidity though can be between 80 and 98% with a average on 90%. Air plates have been used but don’t show up anything.

When I’ve looked online there is loads on temperature control but very little on humidity. The only thing I’ve found is a book on container transport whichever says that butter should be stored at a humidity <85%.

Can anyone tell me whether I’m looking at the right thing? Is the humidity definitely too high?

Any help would be great.

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Posted 18 April 2018 - 03:46 AM

Hi earthbornstew,
You can control moulds in the chill warehouse by regular cleaning, sanitising and fogging with say a Quat.
Moulds are likely to be in the cardboard and maybe the plastic wrapping so always a possible risk.
I personally would be storing the butter frozen to prevent any mould growth then tempering in preparation for use.
Kind regards,



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Posted 18 April 2018 - 01:27 PM

If your internal sampling of the air in the cooler came back negative then I would suspect the packaging from the manufacturer

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Posted 18 April 2018 - 02:33 PM

Go with a flashlight and look for mold in the corners/shelving/floors of the warehouse. Also make sure that the fans on your chiller are being cleaned, and any evaporator pans/condensate lines aren't kicking out spores.


Settle plates aren't great for indicating overall load in the room, and if you're only getting a few butters with mold on them, 30 miinutes of 15cm settle plates may not show the level of contamination you're seeing, which may only be a few spores per square meter in a 24 hour period!


Rather than trying to make your chiller room sterile, I'd try to keep the butter frozen as  Tony said.


The humidity is really high in your coldroom, it should be a relatively dry environment given the chiller constantly removes moisture, is the room open to the outside or receive air pulled from outside? Does the condensate get carried out of the room or drip on the floor/evaporator pan? Are you somewhere tropical? This research states that mold will not grow on the surface of butter if humidity is <70%.


Some discussions on removing humidity from HVAC people here: http://hvac-talk.com...-walk-in-cooler

Austin Bouck
Owner/Consultant at Fur, Farm, and Fork.
Consulting for companies needing effective, lean food safety systems and solutions.

Subscribe to the blog at furfarmandfork.com for food safety research, insights, and analysis.

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