I recall that thread. Much speculation about the colour and packaging.
The colour is within the range for SN
Sodium Nitrite | NaNO2 or NO2.Na or NNaO2 | CID 23668193 - structure, chemical names, physical and chemical properties, classification, patents, literature, biological activities, safety/hazards/toxicity information, supplier lists, and more.
pubchem.ncbi.nlm.nih.gov
(Also explains air exposure)
Vacuum sealing should be fine,just as good as a tub,but you should test it
Ziplock bag guy's Polish SN passed with flying colours.
@x-Ace-x reported he'd opened the bag multiple times for testing,and it was always perfect.
He remarked that it's more robust than we may think.
Ideally,we wouldn't expose it to air whatsoever,until it came time to use it.
During testing keep air exposure brief,and return the bag of SN to an airtight container.
Think about it logically. How would people be able to use it in a lab,or food production without opening it?
Lab grade or reagent would be a better example,because meat curing for food grade involves just a tiny amount of SN,which will be mixed with masses of salt. The effects of nitrAte conversion would be negligible.
Personally,I'm less freaked out about brief,one-off air exposure now