Mold Growth in Vacuum-Sealed Nylon Cotton Netting – Possible Causes?

Good Morning,

I am a Quality System and Compliance Specialist at a small food and food packaging facility. We have recently come up with a situation that has stumped the resident experts here in the facility. One of the items that we produce is a nylon/cotton net that is soaked in a release agent. The net is packaged in sealable bags and the release mixture is applied into the bag from a single head filler that is broken down and washed daily. The release agent has ingredients that deter the growth of mold. The bags that contain the netting is then vacuum sealed and packed. 

Recently we have seen sporadic mold growth on the netting post pack. This is showing up on only one or two products out of around 500. We have been trying to pinpoint where in the process the product is being exposed to the mold and are failing miserably. 

Has anyone encountered anything like this before? I could see if all of a particular lot number showed mold growth, but it is only the one or two items in the lot.

Any ideas would be greatly appreciated.

Thank you

my first guess would be microscopic holes in the vacuum bag

try holding the moldy bags underwater and wait patiently to see if any small bubbles appear (they will be very small)

The product is packed in a vacuum sealed bag that is still holding the vacuum tightly. I am still going to try your suggestion as it is not one that has come up before. Thank you

You've got nothing to lose!   I've had a similar experience with packaged cheese...........teeny tiny holes were the culprit

alternatively, someone is touching the nozzle inadvertently and the contamination flows off with the next fill 

My first guess is that you have an ingredient contaminated with a variety of mold resistant to the antimicrobial properties of the release agent.

You could have a spoiled package tested to speciate what is growing in there.  It is feeding either on the string or the oil (oil seems a lot more likely), and some can be facultatively anaerobic.

I suppose its possible that you're not getting what you paid for with the release agent too.

I would find mycologist and speciate from the molded finished product samples and throughout your environment/process, looking for any parallels.  Secondly I would also be testing the air around your processing line and throughout the facility, also reviewing when air filters have been changed and what Merv rating the filters are.  Even with packaging testing (which is a great idea too) you still have an issue that you need to address.  

I have to admit I'm struggling to imagine what kind of product is involved, apologies but from lots of experience working with mould and products likely to go mouldy, I found vacuum packing more resistant than MAP to mould failure but I've been wrong many times...  But 1 or 2 in 500 is quite a high failure rate for you to be seeing it I'd suggest?

Sounds very boring and predictable but I'd get that team together.  Break it down into the 6Ms of a fishbone diagram and work your way through it.  You might need to go back on your controls on mould and get more data to prove to yourselves you are compliant, or not.  A lot of that will feed into the suggestions above.

But off the top of my head, things I'd look at for mould in packing processes in general (not understanding your process at all) would be:

Method

Are the vacuum settings being run correctly as per your standard settings?

Is the cleaning method genuinely being followed (has anyone watched it?)

Machinery

Are PPMs up to date?  Is there any mould harbourage in your machine?

Is there something snagging your packs?

Material

Are your packaging materials and whatever you're packing contaminated on arrival?  Have you swabbed them and do you routinely?  How are they kept hygienic and is this being followed?  As above, is any packaging getting damaged?  (Note on the water bath idea above, you can get needles you can pump air into the pack through a septum sticker.  That might more effectively show air holes.)

Manpower

Have you watched people in the department?  Is there cross contact from a potential mould source?

Measurement

What are your swab results telling you?

Mother nature

As suggested above, do you have high spore counts in your environmental air?  Have you checked air handling units and do you regularly clean them?

"the release mixture is applied into the bag from a single head filler that is broken down and washed daily"

Could there be water trapped in the system after daily wash that would dilute the release agent at the beginning of a run?

Thank all of you for your insightful suggestions. I am going to systematically eliminate possible root causes using them. I will update with results once completed. Thank you 

@Tara Gordon - All the best in your efforts!