Pasteurization of bulk substrate using Sous Vide

[Genesis]

So I have seen some good teks regarding pasteurization of bulk substrate but they often just involve soaking bags in boiling water for an undisclosed period of time.

Long story short I have access to sous vide equipment and it struck me the other day that this would be the perfect method to pasteurize a large amount of bagged substrate but I am having difficulty finding times and temperatures.

Obviously the bag will need to reach an internal temperature of between 75 and 85 degrees C but is there a set time frame this temperature needs sustained? Or once the core reaches this temperature the bags are pasteurized?

Cheers in advance

[Sallubrious]

That sounds like a good idea.

A large birko style hot water urn would be a good way to do a batch of bags like that.

In theory it should be fine a few minutes after it reaches about 80 Deg, but normally you'd hold it at that temp for 20 mins to half an hour to be sure.

[Etho]

Slow cooker would be perfect....

[migraineur]

I saw someone make a writeup on another forum about using a sous vide to pasteurise substrate. It looked alright for a small amount but I'd rather use gas if I were pasteurising a large amount.

[mimzy]

1.5-2hrs is a normal length of time for pasteurisation of straw.

[Cue]

The true answer for time is 2 weeks.

Now there aren't any of us that are going to do it that long. But it does demonstrate why I like long pasteurization times of 12-24 hours.

The easiest way that I've found is to just put the substrate in large stock pots with tight fitting lids, throw it in the oven. set the oven to the desired temp and walk away. Come back the next day and turn the off, while leaving the substrate in the oven for a slow cool down. The following day its cooled and ready to use.

Pennsylvania, USA use to be big into coal mining. Now for years they have been using the abandoned coal mines to grow mushrooms in. So the university there is big into the study of mushroom cultivation and they have some great info on phase II pasteurization. It gives great info on the how and why. In my search of their link I came up with this one and it seems to have all of that information in it.

http://www.mushroominfo.com/growing-mushrooms/six-steps-to-mushroom-farming/

[Cue]

Here I found a better from the university

http://extension.psu.edu/plants/vegetable-fruit/mushrooms/mushroom-substrate/microbial-activity

Goals of Phase II

Phase II composting is the second step of compost substrate preparation. Regardless how the Phase I composting is done, Phase II must achieve its own important goals. The first objective is to pasteurize the compost substrate making it more selective to give the mushroom a head start growing through this substrate. The compost substrate is pasteurized to reduce or eliminate the bad microbes like insects, other fungi, and bacteria. This is not the complete sterilization but a selective killing of pests that will compete for food or directly attack the mushroom, yet minimize the loss of good microbes.

The second goal of Phase II is to complete the composting process. Since ammonia is toxic to the mushroom mycelium it must be converted to a food the mushroom can use. The good microbes in Phase II convert toxic ammonia in solution and amines (other readily available nitrogen compounds) substances into protein, the more specific food for the mushroom. Most of this conversion of ammonia and carbohydrates is accomplished by the growth of the microbes in the compost. These microbes are very efficient in using Phase I composting products, like ammonia, as one of their main sources of food. The ammonia is incorporated as mostly protein into their bodies or cells. Eventually these packets of nutrients are used as food by the mushroom.

Phase II objectives seem simple to accomplish, but anyone who has tried managing a Phase II may recognize it is one of the most difficult procedures in growing mushroom. Because of a composting or other cultural problem growers sometimes have adjust Phase II programs. Phase II may be managed more than one way, however when changes have to be made controlling the activity of the good microbes should remain constant.

Let us consider both Phase II objectives together since the requirements for one goal may affect the conditions for achieving the other goal. Even through pasteurization occurs over a relatively short time, when and how we conduct the pasteurization affects the growth of the good microbes who condition or convert the food. The mushroom grower manages the temperature and ventilation in the room and compost substrate to achieve Phase II goals.

And it goes on.

So you see we have to look at the substrate as an entire ecosystem.

[Sallubrious]

^ that sounds a lot like the methods commercial growers were using for a straw based compost in Stamets books.

If you use aged horse shit, it's already been through most of the pre-digestion/conversion stages, so it's not needed. Coir doesn't have many nutrients that need to be released but can benefit from pre-composting.

I used to do my pasteurisation in jars which I put in a stockpot on the stove and poked a meat thermometer into one of the jars. Once it got up to about 78 deg I held it there for about 25 mins and it always worked fine for me.

Edited January 27, 2016 by Sallubrious

[Cue]

If you use aged horse shit, it's already been through most of the pre-digestion/conversion stages, so it's not needed.

Even though it may not be needed aged poo is going to be better, because of the beneficial microbes that change the ammonia into organic nitrogen.

This process is called "nitrification through biological fixation".

https://en.wikipedia.org/wiki/Nitrogen_cycle#Nitrification

The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is nitrogen,^[1] making it the largest pool of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition

Organic nitrogen may be in the form of a living organism, humus or in the intermediate products of organic matter decomposition. The processes of the nitrogen cycle transform nitrogen from one form to another. Many of those processes are carried out by microbes,

Nitrogen fixation

Main article: Nitrogen fixation

Atmospheric nitrogen must be processed, or "fixed", in a usable form to be taken up by plants. Between 10x10¹² and 5x10¹² g are fixed by lightning strikes, but most fixation is done by free-living or symbiotic bacteria known as diazotrophs. These bacteria have the nitrogenase enzyme that combines gaseous nitrogen with hydrogen to produce ammonia, which is converted by the bacteria into other organic compounds. Most biological nitrogen fixation occurs by the activity of Mo-nitrogenase, found in a wide variety of bacteria and some Archaea. Mo-nitrogenase is a complex two component enzyme that has multiple metal-containing prosthetic groups.^[6] An example of the free-living bacteria is Azotobacter. Symbiotic nitrogen-fixing bacteria such as Rhizobium usually live in the root nodules of legumes (such as peas, alfalfa, and locust trees). Here they form a mutualistic relationship with the plant, producing ammonia in exchange for carbohydrates. Because of this relationship, legumes will often increase the nitrogen content of nitrogen-poor soils. A few non-legumes can also form such symbioses. Today, about 30% of the total fixed nitrogen is produced industrially using the Haber-Bosch process,^[7] which uses high temperatures and pressures to convert nitrogen gas and a hydrogen source (natural gas or petroleum) into ammonia.^[3]

Don't ya just love microbiology?