Carbon Dioxide Discharge onto Food and Food Contact Surfaces

Hello!  Hoping for a little help since we recently encountered a situation with carbon dioxide that is outside my area of expertise. 

We roast nuts and use CO2 in our fire suppression systems for the roaster.  While there was no fire, we had a minor situation where the carbon dioxide was discharged during processing.  We have confirmed with our supplier that the CO2 is food grade and received a certificate that states the CO2 is 99.9% purity.  However, the CO2 tanks are a carbon steel vessel with an outer aluminum shell.  My research on the issue has yielded inconsistent information, and I am concerned that since the tanks are not "food grade" (like those used for beverage applications) that contaminants could be present.  We have already discarded the nuts that were hit by the CO2, but I am trying to figure out if we need to clean the roaster?  This is not an easy task and requires significant downtime.  What is the likelihood and risk of contaminants being present on the food contact surfaces in the roaster?  

Thanks in advance for any advice!

Jennifer

Hi Jennifer

Interesting situation, however,  CO₂  storage tanks do not need to be food grade as  in usual nut process operation CO₂  does not come into contact with the product. You are using food grade CO₂  as mentioned in your post. Based on these facts in my opinion you do not need to clean the roaster as even if traces of  CO₂  are present in the roaster it will  be in  insignificant amount  and cause t is food grade so it should effect the quality of the roasted nuts.

Kind regards

Dr Humaid Khan

MD 

Halal International Services

Bevrly Hills NSW Australia

Hi Jennifer,

From memory 99% is not the highest marketed purity grade ? I have no idea what defines “food-grade”.

Presumably “food grade” refers to the outputted CO2 and therefore logically assures it is safe to contact food. (in fact the certificate should also state the various impurity levels).

For example CO2 is used for direct contact freezing of food. Presumably this must be food-grade quality.

Just an opinion, never used CO2 myself.

Certainly not a typical forum enquiry!

I think the first step would be to identfy what potential contaminants could occur - presumably corrosion inside the vessel is one, micro unlikely because of the CO2 but there may be others. Have you got a material spec for the tank?

Corrosion of the carbon steel could lead to ferrous particles which may be disturbed into the CO2 during the discharge. It is unlikely that there is an in-line filter so these would pass into the roaster. 

If you have any of the nuts that were in the roaster you could analyse them by atomic absorption to see if there were elevated levels of iron

You may have a sample point on the CO2 tank where you could pass a quantity through a filter for inspection/analysis.

Thank you Foodworker, Charles, and Dr. Khan.  I appreciate your insights as we wrestle with this dilemma!