I have a huge problem. I have been making chicken/sausage gumbo for a few years. The past few times I have made it the leftovers "sour" in approximately 24 hours, even in the fridge. I have changed pots I cook in, changed ingredients, types of meat, etc but it continues to happen. I usually cook the gumbo all day then place into plastic containers when cooled and refrigerate. The last few times it gets foamy on the top and gets a sour smell and taste and I have to throw it out. I have no idea what is causing this reaction. There is a collection of gasses that will even pop the top off my tupperware. Does anyone have any suggestions??