Last post we gave props to a non-native oyster variety. This week I gotta shout out to a local oyster strain we’re lucky enough to have in our culture library. Our Philly Oyster strain started out on a fallen poplar in the fall of 2012 and is the same strain we’ve used for all our Philly Oyster Kits.
Here’s a snapshot of how we make kits. First, I take a benadryl. Then we set up our pasteurizer, which you can see behind me and my assistant. There are a number of ways to pasteurize. Right now our rig is simple- a slightly below-ground, propane-fed burner (the kind you’d use to steam a cauldron of crawfish) with a cinder block firmly set on either side supporting a 55 gallon food grade drum filled 2/3 with water. I use a grill cover and some pillows on top to help break the wind and hold in some of the heat, which really helps during the winter.
Once the burners on and the water’s on it’s way to 170F, we turn our attention to the substrate, first making sure the straw bale is mold-free inside before we shred it. We used to use a lawnmower, but the yellow shredder pictured above does the job a little faster. It’s easier with two people, even if one of them is 3’6″. Oh this is also when the benadryl comes in handy- in addition to oyster spores, I’m allergic to fine particulates of their preferred substrate. Maybe I’m in the wrong business!
The reason we shred the straw is that shredded straw, when it’s ready to be loaded into grow bags, can be packed in much tighter than straw straight from the bale When using sawdust you usually want to avoid packing as it’s already quite dense, but with straw shredding will not only provide more base substrate for larger flushes, the mycelium runs faster when there are fewer leaps to be made between pieces of substrate. Optimally shredded straw averages 4″ in length and is split lengthwise a couple times. Sometimes this takes a second pass. Shredding also abrades the waxy surface of the straw so water can absorb more readily during pasteurization. Oyster mushrooms being over 90% water, this is pretty important.
The next step is loading burlap bags 2/3 of the way full with the shredded straw and tying them off with twine. Fill them up too much, and it’s hard to pull them out when they’re full of water. It’s also pretty dangerous considering you’re hoisting them out of 35 gallons of scalding liquid. At this point, the water should be nearing 170F which means it’s time to toss two bags in. Once in, they need to be pushed down and dunked a few times so they stay submerged. Then, lid goes on, pillow etc. and you set your alarm for 1 hour.
Before pasteurizing it’s important to understand the rational behind it. The point of pasteurizing is to kill off mold spores and bad bacteria while leaving a population of heat-loving bacteria that act as the substrate’s immune system during colonization. The mycelium readily chomps this bacteria up. Other contaminants can outrun mycelium early in the process and render the substrate useless. There is a time-temperature curve for pasteurization. Pasteurizing at 160 can be done in an hour. At 140 it might take 3 or more hours. Over 180 and you’ve over pasteurized at least part of your substrate. You don’t want to under or over-pasteurize. You also have to keep in mind that the further into the core of the bag you go, the longer it will take for that substrate to get to temperature, and the longer it will take to cool once removed from heat. It’s just like cooking a bird and letting it rest. This is much less a factor when using hot water than with steam.
If the straw goes in at 170, the temperature immediately drops a few degrees. The large volume of water holds so much heat that as long as it’s not freezing or windy outside, the water temperature after an hour only drops to around 155 even with the burner off. In the winter I leave the burner on just enough for it to follow the same cooling curve.
Two bags out to drain and cool. Two more in to the same water. You can do a lot of bags, probably 8 or so before the sugars etc. in the water begin to caramelize. Caramelized stuff is generally myco-phobic.
Once the bags cool, we mix with spawn, load bags, seal them and let them sit for a couple weeks. Here, Miss McAtamney’s students at Saul are helping out. By then they’re fully colonized, the mycelium is dense, and they’re ready for fruiting conditions.
Caring for your oyster kit at home is relatively simple but does require daily attention. Winter is the most challenging time to grow mushrooms at home due to dry conditions inside, so extra attention and/or a humidifier nearby help. In the spring and fall, you can basically keep kits outside- outdoor mushrooms are always tastier 🙂
We try to be as supportive of the folks who buy our oyster kits as possible, offering updates like “time to cut those holes!” or “it’s going to be 55 and rainy today, put your kit on the porch!” We’re also experimenting with some new features we hope will lead to more self-sustaining kits = more mushrooms, less work.
If you’re interested in kits, email firstname.lastname@example.org