Yesterday I decided to try pulled pork and this calls for a temp of 165F for 18-24 hrs. I smoked it for 2 hrs then vacuum sealed it up. I always do multiple seals on each end on long cooks so I sealed each end 3 times each one about a 1/4" apart. About 6 hrs in I noticed the water started looking a little bit rusty colored with a slight smokey odor and then after 8 hrs the odor was a little stronger and the water was definitely getting darker. I never had any color in the water when doing other cooks in the past, but I have had the odor of garlic and beef when I would sous vide bottom round roast for 48 hrs at 137F. I thought I must have a leak in the bag so i pulled it out and carefully examined the bag. It was still under a good vacuum and the water inside of it was dark brown so I think I should have been able to see the leak when I flipped it all around looking for any dark liquid dripping out on the white counter. No leak was discovered. I did switch it to a regular gallon freezer Ziploc at this point and just used the water displacement method to remove the air along with the straw suction trick as I didn't want to take any chances, but after further thought I think I could have left it as is.
I wonder if under high temperatures it is possible for the hot liquid to permeate out of the plastic bag but not able to go the other way, and this is increased even more at higher temps like 165F? I looked for a leak for at least 5 mins thinking there had to be one, but it had a couple of cups of liquid in the bag so that was plenty to leak out when I flipped it all over to every direction and forced the liquid around squeezing the bag. I could not get any to force out of even a pin hole if there was one and like I said it still had good vacuum. It was a 5 lb pork shoulder so i'm not surprised at that amount of liquid and do not believe it came from the water bath. I will try double bagging next time but has anyone else experienced this? I think the smoke and the dry rub made the water color more than normal (and made it more noticeable) and I think the higher temperature made it do this phenomenon even worse.