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!
OK I guess I’m a bit confused then… if I cook the kernels in a regular pot for an hour, then let them dry for several hours, what is the sterilization? I thought from your previous description that the cooking step also sterilized them, and then once they were sufficiently cooled and dried I scooped them into a clean jar with some spawn and sealed up the jar?
I used to have a small pressure cooker that fit on the burner, but my ex took that with her. The canner I have will easily do 15+psi and hold it for hours, but this thing is huge… I think it holds something like 18 quart jars?
Ooh wow, yeah that’s a big pressure canner! I work with a smaller pressure cooker - the kind used for preparing meals (a 6L and a 10L, 12 PSI). You probably don’t want to use such a big canner for cooking the grains. I would just boil them them in a regular pot instead.
Usually the procedure is separated into the ‘hydrating’ step and then the ‘sterilization’ step, because this way you can ensure that the grain is hydrated to the right amount, that it is evenly hydrated, and that the surface is dry. It is possible to mix the dry grains and the right amount of water inside of the jar and then just let the grains hydrate while you pressure cook them. Some people online say that they use this method, but I did not get great results when I tried it.
For the sterilization you really should use that pressure canner. Placing the jars inside the canner and running it at 15 PSI for 90 minutes (after venting for 10 - 15 min) is enough to sterilize grain.
But what you have is indeed a big canner… If you don’t want to use it, you can try to simply sterilize by boiling both the grain and the jar. In that case I would not worry about drying the grain at all - the grain would go straight into the jar while both are still hot. Then you have a reasonable chance of not having contaminants. With this procedure you might have grains that are too wet and heat-resistant endospores of bacteria that can survive boiling, so you may get bacterial contamination. But is not a certainty - many times it works fine. Do what’s simplest, and if your contamination rate is above the level that you find acceptable then you can take steps to improve your process.
OK I’ll play around and see what I can make work. Considering I seem to be having good success with the cremini spawn (which was literally just bringing the cardboard and water to a boil and then laying out on the countertop to cool down for about 30 minutes) I’m hopeful that I can pull this off too. I live near Denver Colorado so we’re quite high with a pretty dry climate usually, but we’ve been getting a LOT of rain this Spring so I figure the risk of mold spore is a lot higher that normal.
Anyway thanks for all the advice! Hopefully will be posting pics of some nice grain spawn in a few weeks!
Good luck! I look forward to your healthy grain spawn pics!
You may be seeing pics faster that I expected! It’s been two days since I transferred my original spawn samples to the grain jar, I checked them today and the mycelium is already starting to spread to the grain. I was really expecting to need at least a week or more before I saw any definitive growth, so apparently they are happy.
I do have one jar of popcorn I am concerned about though. That one has little white dots all over the kernels throughout the jar, while all the other jars the kernels are still nice and clean. I’ll be watching that one closely to see what happens, although I’m not sure what would have caused contamination in that particular jar. It wasn’t even the last jar I loaded up. Maybe I’m getting worried over nothing, but I’m sure I’ll probably know in a few more days.
Considering this nice growth, I think I’m going to go ahead and transfer my cremini spawn to its grain jars this weekend. I’m getting nervous that the longer I wait, the greater the chance of getting some contam through the air holes.
Great!!
Hmm, that is suspicious. Did you inoculate using a liquid culture? If you spread the liquid culture throughout the grains, it could look like that… But if your inoculant is more localized (spawn, agar, or tissue) and the whit spots appeared all over the grain, you might not be so lucky 😰
Inoculation was done via grain spawn. I had received 10 grams of spawn from ebay. The spawn itself seemed fine, this was for pink oysters which I split between one jar of popcorn and one jar of rye. The jar of rye is still clean and the spawn is growing in both jars. The white spots actually reminds me of something I see occasionally on fresh sweet corn (which I believe is another type of fungus?), but it just seems weird that it is only appearing in this one jar.
I checked again this morning, the white spots are still there but haven’t gotten any worse, and the oyster spawn is growing. Maybe the oyster spawn will out-compete whatever the white spots are? I know contamination isn’t supposed to get through the fiber stuffing in the jar lid but I went ahead and moved that jar away from the others to reduce the risk of spread… just in case.
So, how is the situation with the white spots? Did they end up being benign?
Not good. The spots themselves have not changed, there’s still the same amount everywhere, but it seems to be greatly inhibiting the growth of the mycelium. There ARE some places where the mycelium seems to be winning and slowly transferring to the popcorn, and in those places the white spots are disappearing, so I’ll give it more time and see what happens.
Meanwhile in the other jars… one of the rye jars has reached the stage of getting that dense white look to it and is nearly ready for a shake&break I think. The rest of the jars are getting pretty heavily filled in, so now I’m a bit confused as to when exactly I’m supposed to do the shake&break? I had thought it was when the light fluffy mycelium reached about 40% of the grain, but now I’m wondering if I’m supposed to wait until the more dense white stuff reaches 40%? Or at this stage does it even matter if I shake it a couple times, or just should I just leave them alone to fill on its own? Regardless, I definitely have several jars that will be ready for fruiting bags soon.