Subject: WHAT KIND OF GASES DOES DECAYING FOOD GIVE OFF?

I put six different food items into 2 liter bottles with a bit of dirt in each 
one.  One bottle contains vegetables, one has fruits, one has meat, one has 
dairy products, one has kidney beans, and one has bread and donuts.  I then put 
a balloon on top of each bottle.  Most of ballons got sucked into the bottle 
then started to inflate.  Two balloons just inflated.  What kind of gases are 
being given off.  My guess is the oxygen in the bottle was used up as carbon 
dioxide was being formed.  But what about methane or hydrogen sulfide?

Re: WHAT KIND OF GASES DOES DECAYING FOOD GIVE OFF?