so what were the yeast eating?

so i bottled my beer the other day, and threw a liter of the slurry in a bottle and put it in the fridge, in case i might need it later. then 2 days later, after it was pretty much all settled out, i opened the bottle to check it out, (i get curious about all the little things) and it immediately started foaming, and going into it's own little fermentation. there were quite a bit of hop particles in the sludge, and about half a liter of "young beer" that was too close to the sludge in the primary to save.

i have heard that eventually, yeast will eat each other. could this be happening already? this was only 16 days after brewday. i didnt think after this long there would be enough fermentable material in the little amount of beer that was in there to do that. is it because of the high concentration of yeast?

i'm really just curious as to why. i need to learn something every chance i get.

A very small amount for fermentables can produce a huge quantity of foam. When the yeast start to rot and autolysis, you will know by the smell.