So this may turn out to be interesting... we'll know in a few hours anyway.
I have some old natto spores in the fridge.
(Disclaimer: I have a brief background in mycology and working with various bacterial cultures. I am not recommending this, I am posting my experience for the informational value. Almost anything could be growing in this...
I grabbed a 1Qt, un-opened carton of non-gmo soymilk sitting at room temp. (About 2 days after h.h. didn't die first. TY for the idea!) The ingredients of the soymilk are whole organic soybeans and water. End of list).
I cracked the lid and put 4-5 squirts of spores from the funky little bottle the spores are in. Immediately screwed the lid back on and mixed it completely by shaking.
I've kept it at room temp and shaken it 1-3 times a day for a week. After the first few days the container puffed up a tiny little bit. I put slight pressure on the container and barely cracked the lid to bleed off the excess gas building up, then closed the lid while it was still offgassing. It did not puff back up any further and has been slightly concave the rest of the time.
Yesterday I put it in the fridge.
Today I opened it and it does not smell funky at all. Definitely not like it has been opened and sitting in warm room temps for a week. It's thicker than regular soy and tastes like soy.
I drank a couple tablespoons a few minutes ago. The kids will call their mother if it's bad. lol
The texture has a fine grainyness to it, along with a slight amount of the bacterial slime feel of cultured natto. The flavor is definitely more complex.