Question

Some juice packages carry the warning "Do not eat or drink if package is swollen." what is the gas produced in this process?

Answer 1

the gas will go from the food stuffs and atmosphere will spoil it

Answer 2

Some juice packages carry the warning Do not eat or drink if the package is swollen. Carbon dioxide gas is produced in this process.

  This is because due to microbial growth which can be because of leakage spoil food stuff and produces $CO_2$ (carbon dioxide) gas by fermentation.

  The production of $CO_2$ (carbon dioxide) causes swelling in the packets and also produces bacteria that may cause botulism. Hence we should not drink such juice as it may cause food poisoning.