What preservative can be used in papadum, papad

I own a papad manufacturing plant in Rajasthan, India. I want to know which type of preservative I can use to increase it’s shelf life.
Papad are prone to fungi, color changes to red, flour come out of papad when it’s dry.
Thanks

Hello,

I do not know about anything about this food. Can you give some information about it ? Ingredients, process, shelf life, storage conditions etc.