not sure if intentional but reporting just incase

Items in backpacks are sometimes represented in a virtual state, meaning there is no physical storage entity or real items, so it's not possible for them to spoil during that time. Backpacks automatically unload when the player is not connected for some time, and load again only when the player next opens the backpack after reconnecting.

What I will most likely do is just disable spoiling of food while in backpacks to make the experience more consistent. Then, if server owners don't want players to use backpacks as a way to prevent food from spoiling, they should disallow food items in backpacks via the plugin configuration. While I understand this isn't ideal, as many server owners want backpacks to function as simply an extension of the player inventory, it's not straight forward to properly implement food spoiling in backpacks.