Which process factors would impact on shelf life of DRY dog meal or chunks/kibbles?In my trouble-shooting have looked at state of crude oil used (PV values&storage),Nature of prdct packaging &also confirmed presence of antioxidants in premixes used.

In my trouble-shooting have looked at state of crude oil used (PV values&storage), nature of product packaging & also confirmed presence of antioxidants in premixes used; however product still yields an off odour/rancid in the 3rd to 4th month period.