well... i've used popcorn A LOT... thats all i used for like two years. it's not that bad at all. It's actually the fastest colonizer I know. It's super easy to get the moisture right. wbs sucks in that department. as far as the endospores go... I had better luck not soaking the corn. if you soak the corn and hatch the endospores, it actually acts against you. because if you let the corn soak even a little bit too long, those bacteria will reproduce exponentially and each one of those new cells will form new endospores. Not sure if you all know how an endospore is formed or not but ... not all bacteria can make them. EACH cell makes an endospore when it is in an environment that is unfavorable... esp. heat. I just did this in a lab last week. we boiled a pure broth culture of Bacillus Cereus for ten minutes... then we smeared out on a slide and did a differential stain.. EVERY CELL produced an endospore within the cell and will eventually lyse. so unless you are really good at telling when you bacteria are hatching, soaking to kill endospores is pointless. better off just going straight to the pc from the bag. And why would popcorn have anymore endospores than any other grain? If you failed at popcorn, you more than likely didn't rinse it well enough. any small amount of starch left over will probably send your jar south. but it's easy to avoid... rinse with hot water, this will keep the starch from coagulating on the kernels. and dry with a paper towel or some kind of towel. if you just leave it to air dry, the left over starch will still be on the kernels until you pc again. you WILL have water in the bottom of your jars after the second pc no matter what, but as long as you dried your kernels, it will be a small enough amount that all you do is shake the jar like mad after you take it out of the pc, this redistributes that water to the kernels in the jar.
this is how I prepare corn... it's really easy.
Popcorn prep. - First, put your corn in the pc without your jar rack (the plate the pc comes with to keep the jars off the bottom of the pc.) and cover with at least three inches of water.
you can probably go a little less once you get the hang of how much the dry kernels will absorb. on average the kernel will expand 3 times it's size.
Now pc at 15 psi for 1 hour. after an hour, turn off the pc and left the pressure adjust back to zero... once the safety nob drops, you can unscrew the lid. be very careful.. the pc will still be very hot. don't let the steam get ya in the face.
Now pour the corn into a strainer. I rinse off the corn with hot water first. the kernels will have lots of starch on them.. if you rinse with cold water first the starch will coegulate making it a bitch to get off. rinsing is a very important part of the process... you want to get the kernels as free from starch as possible. once you've rinsed with hot water... rinse with cold. this will cool the kernels down making them easier to handle and also 'tighten' the kernel up making it not so mooshy.
once rinsed, i let the corn sit for a few minutes to drain. Next i lay down a piece of paper towel and lay the corn on top of that in a single kernel layer. then i place another piece of paper towel on top of the corn layer and roll my hands lightly over the corn.
again, it's not what you use, it's how you use it.