I had a bit of grain left during my last run, so I mixed the bits I had left.
This is interesting, actually. Over the next few months, I'll continue this experiment to see what grain mixes might work better for spawn.
While this wasn't a "proper" test, I had still hypothesized that the higher starch content in the popcorn would do better. I guess not.
I'll try and separate testing into different categories like starch content, moisture content, mycelium strain, etc. There is probably a ton more conditions to isolate as well.
You are very much correct. The mycelium loves cracked kernels as it has easy access to the starch. Since the kernels are hydrated, the shells aren't as much of a barrier in a 100% popcorn jar.
What I find curious is that the mycelium is actively avoiding kernels in a more preferential manner. Since the nutrition value is lower, a slower propagation on the kernels is expected. However, it's just nope'ing around the popcorn until it absolutely has no other place to jump to. It's cool to see that the preference is so distinct.
This begs another question though, and someone else pointed it out: How long do you need to store the spawn for? Slowing down mycelium growth could have its benefits.
Edit: Derp. I completely forgot why the shells can be preferred. If you have to shake or stir your spawn jar to distribute the mycelium, the shells keep the kernels from sticking together as hard.