I've been posting this on reddit, so forgive me if you've already read about it...
I have long had an interest in trying to grow my own mushrooms, but recently started doing a lot of reading to learn the process. I had intended to start out growing a couple types of oysters on cut straw, but while I was collecting supplies and waited for spawn to arrive I ran across an article talking about cutting up clean cardboard, boiling it to sterilize, and seeding it with chopped mushroom stems. I figured this would be a great way to practice and see how much contamination I would get.
Besides the oysters, I wanted to also try cremini/button mushrooms. One of the local grocery stores has them in a bulk bin which appears to not be processed, and it allowed me to pick out some that looked like they came straight from the ground with obvious signs on mycelium still on the base. Great! So I set everything up, drilled some air holes in a small food container, added the cardboard and stems, and put it away in the closet. And then a couple days later I read that creminis actually want a rich mixture of manure and/or grain to grow on. Well crap...
The point was still to watch for contamination though, so I let it continue. A week passed without contamination and I was happy that it appeared I had cleaned things pretty well (and we're talking a very hasty setup on my kitchen countertop in open air). On Sunday, I spotted some white fuzz. Oh boy, this could be it, the experiment is almost over. But then I checked on Monday... and it's not just fuzz, I have actual STRANDS growing across the cardboard. Could it be?!?
Well, today it's still looking pretty promising, and I'm seeing more coming out from various points in the cardboard. It's hard to get a good look at everything because of the humidity, but today is day 12 since I set up the container and there are no greens, blues, or reds anywhere. I am hopeful, although frankly amazed at what seems to be happening.
In the meantime my oyster spawn arrived but it was less than expected so I have picked up some quart jars and am waiting to receive some rye grain. I have blue and pink oyster spawn which I will split between two jars each to expand before trying to move it to grow bags with straw. It will take a little longer than planned but I'll get there. And I'm waiting for my container to be fully colonized with the unexpected spawn (or to see a definite sign that it is NOT mycelium) and then I'll get that transferred to a grain jar as well.
However it goes, I'm having fun!
Yeah! Look, here I have two jars of popcorn kernel grain spawn. On each one of the jars I put in a small piece of a King Oyster mushroom that I bought in the supermarket. I rub 70% isopropanol around the mushroom and then I tear the mushroom open and take out a tiny piece of issue from the inside. These jars were inoculated on May 16, so this is 23 days of growth:
The left one I already shook and the right one is still un-shaken.
What I mean about the hydration is that with rye grain I would often end up with grains a bit too wet and sticky, making it impossible to shake the spawn properly. The colonized grain would turn into a hard block that I had to take out with a spoon! With properly hydrated and surface-dried grain, you can shake the grains and they separate very well, making it much easier to work with them.
What I do is I buy one of these bags from the supermarket (900 g, cost is about $2.5 per kilo or $1.13 per pound):
No need to pre-soak them. I cook them in the pressure cooker for 25 - 30 minutes, starting the timer once pressure is reached without venting (this is not a sterilization step, just a cooking step). Without a pressure cooker they can be boiled for about 1 hour. Then I place them in a colander to dry - at least one hour, over night is even better. The grains should not be wet outside and they should still be firm, but it should be possible to crush them between your fingers if a moderate amount of force is applied.
Since each person has a different setup, the best way to get the right hydration for your own setup is to measure the amount of water absorbed a few times until you are happy with your procedure. You weight the grains before cooking them, and you weight them again after cooking and drying them. The increase in weight for popcorn of 40% - 70% would be a good amount of hydration.
$17 for 4 pounds of rye is quite expensive... That comes out to 4.25 / lb! Current prices I can find for my region are closer to $0.5 / lb for buying bulk. So for a mushroom farmer that buys rye in bulk from as close to the source as possible it makes a lot of sense to use rye because it is a really good grain and cheap, but when it is not sold locally and you have to order it from a specialty shop you are paying a high premium for it! Hope that makes sense!
RE: the rye grain... yeah I agree that was way expensive! I'm not doing anything in bulk though and don't really have the space to go crazy with all this, but at the moment I haven't even been to the local stores to see what's available. The popcorn should be real easy to come by, though. One thing I did see, though, was adding gypsum to the water while cooking, which is supposed to help prevent the grains from sticking to each other. It looks like they're suggesting about one tablespoon of gypsum per 5 full quart jars of dry grain. I wonder if this would help with the popcorn too?
So a couple questions here about the popcorn... If you cook it in the pressure cooker, is that done inside the mason jars or just directly in the pressure cooker with some water? I have one of the big ones for canning, so it seems like cooking directly would be more efficient just in a regular pot, and I'm guessing since you are trying to cook them at this stage you're talking about doing it this way.
And for either method, do you add enough water to completely cover the amount of kernels you put in the pot, or do you only put a little bit of water in the bottom? And while the kernels are drying afterwards, do you do anything to protect them from picking up any contaminants?
So this morning's viewing of my cremini spawn... whatever is growing in there is definitely expanding. I'm seeing long white strands on all four sides of the container now. I think I'll try to hit Walmart today to find a tub I can use to make a still-air box so I have at least a little control over contamination when I transfer my various spawn to the jars. Hoping to get some jars going this weekend.
I do add some gypsum some times, and sometimes I don't add it. I think the main benefit is nutritional in that it adds some calcium. It can help dry out the surface of the grains a bit if you add it after cooking the grain, but it only helps to a degree - if your grains are over-hydrated or too wet, gypsum will not be enough to stop them from becoming a hardened block.
As for pressure cooking the grain - this is done with the grains directly in water with more than enough water to cover them. I use the pressure cooker in this step just because it is faster and more efficient. The rate at which grains absorb water is proportional to the temperature, and the liquid water gets hotter in the pressure cooker due to the increase in boiling point at the higher pressure. This rate depends on the pressure achieved by your pressure cooker (usually 12 PSI or 15 PSI), and a bit in the altitude. That's why the best is to test the hydration with your setup instead of relying on a set recipe.
There is no need to protect the kernels while they dry. The sterilization step comes after, once the grain jars are prepared. In theory you can get unlucky and an heat-resistant endospore could land into the drying grain, so you might want to be a bit clean. I personally I just let it dry by the sink. Get them out as soon as possible while they are hot because this helps the water on the surface evaporate quicker. You can even use a towel to dry them but I find that rubbing grains with a towel is a bit awkward.
That's great! Exciting :D Good luck!
Random trivia: it's actually not the liquid water that matters, it's the water vapor due to the pressure-temperature relationship of water in the gas phase (since gasses are significantly more compressible than liquids). It's also important to note that water vapor does not behave like an ideal gas above ~1.5PSI, and it has a different temperature-pressure curve than gasses like N2, O2, and CO2, which is why you need to purge air at the beginning of the canning process in order to achieve a high enough temperature.
...and yeah, it's crazy how altitude and atmospheric pressure matters, the weight of the air around us is literally pushing down on the rocker weight, affecting the relative internal pressure.
Thermodynamics is pretty awesome! XD