Sterile when it arrives

A sterile bag is a moment, not a permanent property: the filter breathes, time passes, and opening it does not help it breathe.

What the word means, on the day it arrives

Sterile, on a bag of grain or wood, does not mean the courier, the box and the landing are sterile. It means the contents went through a pressurised steam cycle, around 121 °C, and were closed with a filter before room air could get back in. At that moment, inside, there was nothing alive beyond whatever the cycle failed to kill — and a cycle done properly leaves that “beyond” very close to zero. The outside of the plastic never had this claim. You can set it on the table. You do not have to flame the surface. You do have to avoid puncturing it, peeling the filter, or turning condensation into a liquid bridge through the patch.

The phrase “sterile on arrival” is therefore a tense, not an eternal label. At the moment the cycle closed, the contents matched that word. Every day after, the filter does its job, which is to let gases through and hold particles back. Holding back is not a magic wall forever. A dry, intact filter is an excellent slowing. A wet filter can act as a wick. A filter that is creased, detached, or covered in damp dust for months is a slow door. The bag forgotten on top of a cupboard from March to October is no longer the object that left the autoclave, even if nobody opened it and even if the plastic looks the same.

That is why you inoculate near arrival, you keep cool whatever has to wait, and you learn to recognise a bag that is already lost before you give it a syringe. A living syringe in a bag that is already occupied does not “win because it is good mycelium”. It finds the place taken, or at best it shares the food with someone who had weeks of a head start.

The filter is not a hole, and it does not need help

The filter on these bags is a patch, generally a fabric or a membrane with pores narrow enough to stop spores and bacteria when it is dry, and open enough to let carbon dioxide out and a little oxygen in. Mycelium respires. A volume closed with no exchange at all accumulates CO2 and, over time, slows down. The filter is the exchange. Opening a corner “so it can get some air” replaces that filtered exchange with kitchen air, which is full of mould spores and flour dust. You do it at the moment the grain is still bare, which is when the race is easiest for whoever arrives from outside.

A bag that looks tight is not suffocating for lack of a hole. It is tight because the seeds are swollen, or because a little gas has not left yet, or because the temperature rose and the internal air expanded. You move the seeds that are pressed against the filter, from the outside, so the patch is clear again. You do not puncture it with a needle “to vent”. That hole does not close the way an injection port does, and it does not filter. It is a hole. If the swelling increases day by day and the smell through the patch is sweet, sharp, of solvent or of a cellar, the gas is not the clean respiration of mycelium. It is fermentation. The bag is already lost. You do not open it to confirm the smell: the smell has already arrived. You bag it and discard it.

You do not wet the filter to clean it. Seventy percent alcohol belongs on the port, on the bench, on your hands. On the patch, a liquid can cross pores that stopped particles when dry, and drag in whatever was sitting on the outside dust. A patch that is damp after a journey in the rain, or after the parcel sweated in a van, is a reason for suspicion, not a reason to dry it with a tea towel. You let it equilibrate indoors, you look to see whether the inside has a puddle, and you decide.

The injection port is the other opening, and it is made to close again after the needle. It does not exchange air. It does not replace the filter. Wiping it before inoculation makes sense. Peeling it off “to let the bag breathe” does not. If the port is already punctured, dirty with soil, or the seal around it is lifted, treat the bag as compromised: this is not the moment to discover whether today’s needle still goes in neatly.

Cold, not freezing, and not the sun in a van

Cold slows things. It does not sterilise and it does not resurrect. A bag of grain not yet inoculated, held between 2 and 8 °C, keeps still the few organisms an imperfect cycle might have left behind, and it keeps the water more stable. Condensation makes fewer trips from the plastic to the seed. Mycelium, if it were already there, would grow slowly. The same window applies to liquid cultures: the fridge, never the freezer. Freezing crystallises the water inside hyphae and ruptures them. A bag of raw rye alone, frozen, does not become “more sterile”. It becomes a seed whose hydration is damaged, and on thawing the water comes out where it should not.

Heat does the opposite. A bag in a car in the sun, or set on a radiator so it “warms up before the syringe”, pushes any survivor to grow and moves vapour around. The right warming is room temperature, for a few hours, before you inoculate, so you are not shooting living liquid into a frozen block. It is not a cooking. A substrate that arrives still hot from your own autoclave, if you sterilise yourself, has to come back to temperature for another reason: residual heat kills the inoculum. The bag that arrives already sterile and already cold does not have that problem. It has the opposite problem if you leave it for weeks in the warmth.

Wood blocks take more space than a kitchen fridge. A cool, stable place, in the dark, under twenty degrees, is already better than a summer cupboard. It is not the cold of the milk. It is the absence of swings. Swings are what rain condensation onto the filter and the grain. If you can fit the grain in the fridge, do that. If the wood sits in a dry cellar, keep it off the floor, not against a wall that sweats. Outside humidity wetting the filter is the same wick story.

How long that bag still is

There is no single honest number that holds for every attic and every July. There is a line of reasoning. A bag used within a couple of weeks, kept cool, is the object the sterilisation cycle was describing. After a couple of months, especially if it has seen heat, you are asking the filter and the seal for a hold that was not an eternal contract. If there is a date on the packaging, that date outranks your wish to “try it anyway”. If there is no date, do not invent a comfortable expiry. Look at the signs. A good bag at three weeks gets inoculated. A doubtful bag at four months gets discarded closed, and that is less waste than a straw substrate contaminated afterwards.

Liquid culture ages by another route. Mycelium in broth is not a powder. It consumes, it fragments, and if a bacterium entered on the needle it grows even in the fridge, only more slowly. A six-month syringe is not the same syringe as last month’s, even if the liquid is still clear. Clear does not prove vitality. It only proves there is no obvious cloud. A cloudy broth, filamentous in a way that differs from the mycelium you knew, or with a sour smell at the cap, is not injected “to see”. You see it in the grain, a week later, when it is late.

The signs of a bag already lost

You look before you wipe the port. Against the light, you shake gently. The seeds should move. Clear condensation, appearing after the move from cold to warm, is often physics: vapour has settled on the plastic. On its own it is not a conviction. A milky puddle, seeds glued into a jelly, a pink, orange, black or green colour, a white you did not sow: the bag is occupied. Someone grew in the time the bag was waiting. Inoculating it is handing fresh food to that tenant, or at best dividing the volume into an unreadable map.

The smell, near the filter, without opening: there cannot be a fresh-mushroom smell if you have not inoculated. A neutral smell, of cooked grain, is what you expect. Sweet, sharp, of cheese, of rubbish, of solvent: lost. A filter that is detached, punctured, or sodden and dark is lost even if the seeds look all right, because the guarantee was the filter. A bag swollen like a balloon, that swells back after you have pressed it gently from the outside, is producing gas. Healthy, uninoculated grain does not ferment.

Wood is harder to read. A sterilised block can have condensation and an even sawdust colour. Spots, a rotten filter, a sour smell, mould on the patch: lost. A dry, shrunken block, with no spots, is not “lost” to contamination. It is bad food. Mycelium enters it with difficulty and does not consolidate. You do not wet it by opening and spraying. You recognise it and you do not build a week of waiting on top of it.

What you do not do, faced with a lost bag, is the rescue. You do not reboil it in an ordinary pot, which will not sterilise a kilo that is already contaminated and will wet the filter. You do not open it on the balcony “so as not to dirty the kitchen” and shake it: the spores come out anyway, and the balcony is not a void. You put it in another bag, you close it, you discard it with the rubbish. Open compost, for a green that is sporulating, is a way of sowing Trichoderma into the garden you then walk back from.

Three arrivals, one reason

The biological calendar is awkward to keep in mind, and bags take up room. The temptation is to buy a stock and forget it. A stock is the opposite of “sterile on arrival”. An arrival close to the moment of use is the same idea, repeated.

The Rye Club is one kilo of sterilised rye a month. The point, here, is not having a subscription. It is not piling up ten kilos that age while you colonise the first. You inoculate the bag that has just arrived, when the filter has had a few days of the world and not a season. If you skip a month, the bag waiting in the fridge is still worth a few weeks. It is not worth “it is already paid for, I will use it at Christmas”.

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The Hardwood Club is a sterilised beech block, two kilos, every month. Supplemented wood, or even wood that was only sterilised, does not stay a blank page for a year. The edges dry, the filter lives, a rare survivor has time. A block that arrives and is spawned that month is aligned with the cycle. A stack of blocks “for when I have time” is a stack of sterility going quiet as it lapses. The spawning gesture does not change: already colonised grain spawn, mixed in cleanly, or the path of the bag that already holds grain and wood together. What changes is the age of the wood.

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The Culture Club is two liquid cultures of ten millilitres a month, one classic species and one in rotation. A culture is alive. It ages in the broth even well capped. Having a syringe when you need to inoculate, instead of a syringe that has spent the summer in the fridge door, is the same logistics as the bag: vitality is a time, not an object to collect. The rare species that arrives and sits three months in the dark is a species you inoculate tired, or that you do not inoculate. The cold holds it. It does not freeze it at the age it had on arrival day.

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None of these arrivals corrects crooked hygiene. A fresh bag, opened on the chopping board, is lost in a minute. An old bag, kept closed and inoculated well, sometimes still works. The difference is probability, not a moral. You play on the side where the filter has worked little and the hyphae in the syringe are still the ones you could see against the light, white filaments, not a fog.

How the inoculation day is handled

You wipe the bench. You move away plants, fruit, the flour board. Hands washed, 70% alcohol on your hands and on the port, a new needle or one passed through a flame and cooled in the air, without setting it down. Two or three millilitres, several points, cap back on the syringe, fridge for the rest. A label. Then the bag is not opened for any “check” until it is time, much later, to join the spawn to a substrate — and even then you open the minimum, with spawn that is already white, not out of curiosity.

If the bag that has just arrived has a visible defect, a torn filter, an open seal, seeds in a slime, you do not inoculate “since it is here now”. You set it aside closed and you treat it as lost. Inoculating so as not to waste the syringe wastes the syringe and, if you then use that grain, wastes the straw too. The syringe can wait in the fridge for a few weeks. A doubtful bag does not improve by waiting.

What this guide is not

It is not a printed expiry date and it is not an invitation to keep stocks. It is why “sterile” is conjugated in the recent past: it was, when the steam stopped, and since then the filter, the heat and the calendar decide whether it still is. Opening it does not renew the cycle. It ends it.