A quick background. Our company produces fully cooked vegetable products going into a sealed plastic bag for packaging. This product is chilled on site (maximum 55F), but is shipped 1 hour on a reefer truck to go through a full blast freeze. We have recently had issues of product bags getting very bloated with excess air. I believe that our issue is just getting excessive air in the package to begin with, then after sitting in a blast freezer where air temperature is -50F the air is simply warming back up and expanding (bloating) air in the bags. However, other members of the food safety team believe this could stem from microbiological activity within the product releasing CO2 and expanding packages. I don't believe this is the case, as product is not bloated at arrival at the blast freezing facility, and time isn't sufficient in the 5 hours from packaging to being fully frozen to bloat packages so severely. Has anyone else faced this problem of sealed plastic bag type packages bloating or inflating upon temperature change? What are some strategies to avoid this? We are currently destroying any product that is bloated on the off change that it is caused by a microbiological issue.