Pink curing salt turned yellow - safe to use? I have a bag of pink curing salt (Prague powder / instacure) #1 that has been in a cupboard since November 2019. It has been stored in its original packaging: a zip-lock style bag, which I have opened and resealed several times. The seal has been reinforced with a clip. The powder has now turned yellow, and I can't figure out why or whether it is still safe to use. Curiously, a plastic container containing a mix of the curing salt with sugar and 'regular' salt has kept its color, while being stored next to the bag of discolored salt.
I know the pink color comes from food coloring which could oxidise or be affected by light, but why would this only have happened to one of the two containers?
The discolored salt:

The mix of curing salt with sugar and regular salt:
That's our brand &quot;Home Curing UK&quot; or &quot;Surfy's&quot;.
The colouring used at that time was a natural colouring. Unfortunately the colour deteriorates over time due to the action of light and the nitrites, however the loss of colour does NOT in any way affect the efficacy of the product, 100% guaranteed.