Pasteurized Supplemented Hardwood Substrate
The general consensus in my reading so far, and what I have been basing my process on, is that subsidized substrates must be sterilized to avoid contamination. Some articles are stating that pasteurization is possible, in lieu of sterilization, when the substrate percentage is less than a certain threshold, somewhere between 10 and 30 percent.
I’m finding that the bottleneck in my process currently is definitely sterilization; I am using a single 23 Quart pressure cooker to sterilize substrate. I am considering the purchase of a second pressure cooker, however, I’d first like to be certain that all of this is necessary.
Obviously, there is some credible research out there and Master’s Mix (50/50) has been adopted by many different cultivators as the go-to substrate for Oyster and Lion’s Mane mushrooms.
So, to test this out, I am creating a bunch of substrate bags with different percentages of supplement (soy hulls) to hardwood. Also, I am using sterilized supplement in some and pasteurized supplement in some. Ideally, the result of this experiment would be that low supplement ratios are as good as better than high supplement ratios in terms of yield and that pasteurization does not compromise the substrate in terms of incidence of contamination.
The bags I have created are 16oz bags as follows:
For each subsidization ratio, I have created a bag that includes pasteurized soy hulls and a second bag that includes sterilized soy hulls. Every bag includes pasteurized hardwood pellets. Additionally, every bag was inoculated with Lion’s Mane grain spawn at a 1:8 spawn ratio (i.e. approximately 2oz of grain spawn in each bag).
One other thing to note is that, although I used gloves and 70% isopropyl alcohol and good sterile technique, I created these bags outside of a still air box and without the use of a flow hood. I have placed these bags into the dark room for colonization. I will update this article with results.
Update — April 13, 2023
After 4 days I am seeing mycelium growth in all 10 bags. I am seeing more growth in the bags with 30% and higher. So far, there are no signs of contamination.
Update — April 20
After 11 days I am still seeing mycelium growth in all bags. There is no contamination. Growth seems slow. Continuing to monitor.
Update — May 1
Today I moved all of these tiny grow bags into the grow room. Both the pasteurized and sterilized bags at 30% and higher are clearly colonizing faster than those at 20%. Interestingly, the only bag that seems to be showing signs of possible contamination is the 10% sterilized bag. I’m continuing to monitor.
Update — June 8
I took several photographs on different days. I stopped being so focused on the experiment, however, because mushrooms were growing on all bags. The only bag that had signs of contamination was the 40% pasteurized bag. I will leave interpretation of the following pictures to the reader:
