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!
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Cool! Good luck!! It is super fun :-)
I know that rye grain is often recommended - and it makes sense for commercial growers who can get lots of cheap rye grain and who have mastered the process of hydrating and sterilizing rye. But I have personally moved back to popcorn kernels… I can buy them at my local shop, it is easy to hydrate them to the right level, and I have less contamination. I mention this because I read that you are “waiting to receive some rye grain” - which sounds like you may have ordered it online! Consider that you can get similar or even better success with the grains that are readily available.
If you have any doubts about contamination you can post some photos and I might be able to help!
Really, popcorn? I’ve seen a couple mentions but hadn’t read anything definitive on it. What do you do to get the right hydration? From what I’ve been reading, the process for rye grain is to basically wash them, then soak for 12-24 hours, cook it for about 15 minutes, then let it dry out for a couple hours before tossing it into jars for the pressure cooker. I’m guessing the popcorn kernels are somewhat similar?
I only ordered the rye online because I was too lazy to check the local stores, and wasn’t in a huge hurry anyway. The package I got was $17 for four pounds but I figured there would be better deals if I had shopped around.
As for contamination, it doesn’t really look like mold, and certainly isn’t spreading as fast as mold does, so I’m holding out hope so far. I figure by the time it’s fully colonized I’ll be able to get some decent pictures. Or even if it’s mold. Right now I’m trying to keep it in the dark as much as possible.
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.
So this morning’s viewing of my cremini spawn… whatever is growing in there is definitely expanding.
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
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!
Looks like I’ll be prepping my grain jars tomorrow. The rye showed up in the mail yesterday and I picked up some popcorn kernels today. I have both rinsed and soaking in water tonight, the goal is to make three jars of each to I can try all three types of spawn in both types of grain. I also picked up a storage bin that I think is about the right size to make a still-air box. So the plan tomorrow afternoon is to get both grains cooked, loaded into jars, and sterilized in the canner, then let them cool overnight and I’ll get my spawn added to the jars Monday after work.
Oh, and the oyster spawn I got off ebay, they have both taken off like crazy sitting in the closet, so should be ready to go for the jars. The cremini spawn is still growing, but very slowly. I think that stuff is going to be a lot happier once it gets put in the grain jars, but at this rate it’ll probably be another week or two. Still, I’m excited that things are starting to progress!
Yeah apparently I WAY overestimated the size of the canner. It actually holds 20 pint jars, or 7 quart jars. Haha oh well. The popcorn expended more than expected so I ended up making four quarts and still tossed some out, but the squirrels will be happy. So I have another half hour under pressure and then I can shut it down for the night (and my back is killing me!)
Jesse, we need to grow mushrooms !
