Wort pH and Risk of Botulism

[marc1]

I found this reputable source regarding sterilization with a microwave

https://www.cdc.gov/infectioncontrol/guidelines/disinfection/sterilization/other-methods.html
As you see, the maximum which is considered is 5 minutes for a home-type microwave oven. Other sources indicate 1 minute sterilizes all but the most "robust" microbes.

For what is of interest to homebrewers, whose goal is normally sanitization rather than sterilization, microwave ovens are absolutely useful.

I won't bet about unicorns, though

PS This source indicates heat as the real sterilizing agent, and maybe radiation itself. For what I have read though (where? I don't know) it's really the explosion of the microbe from inside which is deadly. That should certainly include the spores of botulinum, if that mechanism is actually in place. Regardless, microwave ovens as a means of sterilization is a reality.

That's not what that says.

" Of concern is that home-type microwave ovens may not have even distribution of microwave energy over the entire dry device (there may be hot and cold spots on solid medical devices); hence there may be areas that are not sterilized or disinfected."

Then also:
"The use of microwave ovens to disinfect intermittent-use catheters also has been suggested. Researchers found that test bacteria (e.g., E. coli, Klebsiella pneumoniae, Candida albicans) were eliminated from red rubber catheters within 5 minutes. Microwaves used for sterilization of medical devices have not been FDA cleared. "

Botulism spores are a lot more hardy than yeast and regular bacteria, so this also doesn't indicate safety.

If you want to kill germs on your dish sponge, home microwaves are great. They shouldn't be used to "sterilize" perishable food for room temperature storage.

 

[bu_gee]

I found this reputable source regarding sterilization with a microwave

https://www.cdc.gov/infectioncontrol/guidelines/disinfection/sterilization/other-methods.html
As you see, the maximum which is considered is 5 minutes for a home-type microwave oven. Other sources indicate 1 minute sterilizes all but the most "robust" microbes.

For what is of interest to homebrewers, whose goal is normally sanitization rather than sterilization, microwave ovens are absolutely useful.

I won't bet about unicorns, though

PS This source indicates heat as the real sterilizing agent, and maybe radiation itself. For what I have read though (where? I don't know) it's really the explosion of the microbe from inside which is deadly. That should certainly include the spores of botulinum, if that mechanism is actually in place. Regardless, microwave ovens as a means of sterilization is a reality.

From the article, and salient to my point about unicorns:

Of concern is that home-type microwave ovens may not have even distribution of microwave energy over the entire dry device (there may be hot and cold spots on solid medical devices); hence there may be areas that are not sterilized or disinfected.

While it is true that for most brewing sanitization is sufficent, for the case of C. botulinum (I always thought it was botulini, live and learn) sterilization is a minimum standard. Also, I may have missed it, but I didn't see where they were taking about C. botulinum in particular or even the Clostridium family in general. The only mention of it is in a process called "vapor-phase hydrogen peroxide" which I can make guesses on, but it is well outside the scope here.

The radiation source for sterilization they talk about is gamma rays from a Co-60 source. Microwaves have less energy than visible light, which has less energy than UV, which has less energy than x-rays which has less energy than gamma rays. You're talking several orders of magnitude of energy here.

 

[Birrofilo]

While it is true that for most brewing sanitization is sufficent, for the case of C. botulinum (I always thought it was botulini, live and learn) sterilization is a minimum standard. Also, I may have missed it, but I didn't see where they were taking about C. botulinum in particular or even the Clostridium family in general. The only mention of it is in a process called "vapor-phase hydrogen peroxide" which I can make guesses on, but it is well outside the scope here.

Well, they talk about "sterilization" which, when reached, implies that also all bacteria of the Clostridium genus will be killed, otherwise it's not sterilization in medical terms.

It's a sufficiently good unicorn for our purposes and, if we exclude spores, it's also sufficiently good for the vast majority of laboratory works. I do presume that it is good for spores as well but that's not the central part of the message, which is "your microwave oven can be very useful for your homebrewing actitivity".

Just as another example, if for some unexpected problem I need to sanitize a bottle or two during a bottling session, I do that with the microwave: just put a glass full of water in the oven and a bottle (or two 50cl bottles) with a little water in them. 40 seconds and that's it. Don't do that with bottles which have labels which contain metallic parts (labels can use metals).

 

[bu_gee]

Many homebrewers use dried yeast from opened and re-sealed packs which is completely sealed from oxygen, self-sealed from oxygen (with one of those home machines to make vacuum) therefore not commercially canned, and won't be cooked before eating.

As a side note, industrial beers are not sterilized (only pasteurized) and many "craft beers" are not even pasteurized, yet they pose no risk of botulinum, even though their acidity is less than what appears to be considered safe by some.

Let me be clear, there are several things that keep C. botulinum at bay. The methods that we keep them from growing, from (what I believe to be) most common to least common are: oxygen exposure, dehydration, high-acidity environment, and high-ethanol environment.

Failing that, we use heat treatment to feature the toxin.

There are probably more, but many of the products that haven't sterilized the C. botulinum listed here use one of more of those methods before they use cold.

Many products that require no refrigeration are sold in a refrigerated case because of people's perception of the product. For example, Velveeta requires no refrigeration until you open it, yet because people perceive it as cheese, they sell far less of it if they put it elsewhere in the store. Refrigerated canned ham may be the same way. That is, because it is sold refrigerated doesn't mean it requires refrigeration. Best example of this, however, is beer.

 

[bu_gee]

Well, they talk about "sterilization" which, when reached, implies that also all bacteria of the Clostridium genus will be killed, otherwise it's not sterilization in medical terms.

It's a sufficiently good unicorn for our purposes and, if we exclude spores, it's also sufficiently good for the vast majority of laboratory works. I do presume that it is good for spores as well but that's not the central part of the message, which is "your microwave oven can be very useful for your homebrewing actitivity".

Just as another example, if for some unexpected problem I need to sanitize a bottle or two during a bottling session, I do that with the microwave: just put a glass full of water in the oven and a bottle (or two 50cl bottles) with a little water in them. 40 seconds and that's it. Don't do that with bottles which have labels which contain metallic parts (labels can use metals).

Please look at the OP. This is about canning wort. This is explicitly about not excluding spores.

Sanitization and sterilization is usually defined in terms of target species. Sterilization from, say, salmonella, an acidophile, is a very different beast from a thermophile. Assuming they are the same is asking for a trip to the hospital.

 

[Birrofilo]

That's not what that says.

I quote a large stretch:

" The initial reports showed microwaves to be an effective microbicide. The microwaves produced by a “home-type” microwave oven (2.45 GHz) completely inactivate bacterial cultures, mycobacteria, viruses, and G. stearothermophilus spores within 60 seconds to 5 minutes depending on the challenge organism933, 935-937. Another study confirmed these resuIts but also found that higher power microwaves in the presence of water may be needed for sterilization932. Complete destruction of Mycobacterium bovis was obtained with 4 minutes of microwave exposure (600W, 2450 MHz)937. The effectiveness of microwave ovens for different sterilization and disinfection purposes should be tested and demonstrated as test conditions affect the results (e.g., presence of water, microwave power). Sterilization of metal instruments can be accomplished but requires certain precautions.926. Of concern is that home-type microwave ovens may not have even distribution of microwave energy over the entire dry device (there may be hot and cold spots on solid medical devices); hence there may be areas that are not sterilized or disinfected. The use of microwave ovens to disinfect intermittent-use catheters also has been suggested. Researchers found that test bacteria (e.g., E. coli, Klebsiella pneumoniae, Candida albicans) were eliminated from red rubber catheters within 5 minutes 931. Microwaves used for sterilization of medical devices have not been FDA cleared. "

This note quotes some different studies, which arrived largely at the same results, that is that a home-type microwave oven completely inactivates not just bacteria, but also spores (although only one genus is cited) and viruses ("initial report"). That's a lot. That's within 5 minutes. The other study confirms that but suggests water and higher energy (W) is needed than in the previous study (we don't know the wattage of the initial report.
Sterilization of metal instrument can be achieved, which is very important for laboratory work and for homebrewing.
Yes, there is a caveat with "cold spots". This requires some excess sterilization. It says "of concern" it doesn't deny the validity of the procedure.

Again, this is a tool in our toolbox. Other sterilization procedures (by alcohol, chemical substances, boiling, vapour etc.) will have their own set of pros and cons.

The message is that a microwave oven definitely provides a way to sterilize things and food, with some asterisks.

Actually in my ignorance of the subject I can hardly find another sterilization means which is so broad in scope. Chemical substances generally are effective against one subset of microbes, and the same for acids. Boiling requires a lot of effort to be sure to destroy spores, from tenths of minutes to hours depending whom you ask to. Autoclave costs, etc.
A simple and humble microwave oven, which is in every house, is reported by some scientific experiment to kill everything including spores in 5 minutes. That's what I bring home.

 

[bu_gee]

Please look at the OP. This is about canning wort. This is explicitly about not excluding spores.

Sanitization and sterilization is usually defined in terms of target species. Sterilization from, say, salmonella, an acidophile, is a very different beast from a thermophile. Assuming they are the same is asking for a trip to the hospital.

I should add that there is no universal form of sterilization. The medical definition of sterile probably has a very specific definition in terms of how many of a particular type of organism can exist.

 

[Birrofilo]

Please look at the OP. This is about canning wort. This is explicitly about not excluding spores.

Sanitization and sterilization is usually defined in terms of target species. Sterilization from, say, salmonella, an acidophile, is a very different beast from a thermophile. Assuming they are the same is asking for a trip to the hospital.

Until today I thought that the broad definition applied, as in here:
https://en.wikipedia.org/wiki/Sterilization_(microbiology)
I understand that sterilization from salmonella requires different sterilizing agents than a sterilization against a thermophile etc. But for what I know, if something is "sterile" this means there is nothing in it that can reproduce itself, whatever it is.

I understand the OP wants to can wort, but I dont' understand whether he wants to use it "as is" after opening the can or he wants to boil it.

I agree with you that using the canned wort "as is" would be a Russian roulette. But as we saw a few minutes of boiling will clear the risk of botulinum. That might make the goal of the OP feasible.

 

[bu_gee]

I quote a large stretch:

" The initial reports showed microwaves to be an effective microbicide. The microwaves produced by a “home-type” microwave oven (2.45 GHz) completely inactivate bacterial cultures, mycobacteria, viruses, and G. stearothermophilus spores within 60 seconds to 5 minutes depending on the challenge organism933, 935-937. Another study confirmed these resuIts but also found that higher power microwaves in the presence of water may be needed for sterilization932. Complete destruction of Mycobacterium bovis was obtained with 4 minutes of microwave exposure (600W, 2450 MHz)937.

snip

A simple and humble microwave oven, which is in every house, is reported by some scientific experiment to kill everything including spores in 5 minutes. That's what I bring home.

That is very much not what this article is saying, especially since it talks about Clostridium species elsewhere in the article. If you're worried about G. stearothermophilus spores, then you're good, but this is about C. botulinum.

 

[bu_gee]

I understand the OP wants to can wort, but I dont' understand whether he wants to use it "as is" after opening the can or he wants to boil it.

I agree with you that using the canned wort "as is" would be a Russian roulette. But as we saw a few minutes of boiling will clear the risk of botulinum. That might make the goal of the OP feasible.

This was my proposal in #46.

 

[bu_gee]

This was my proposal in #46.

But to be 100% clear, it is botulinum toxin, not C. botulini itself that boiling fixes.

 

[Birrofilo]

That is very much not what this article is saying, especially since it talks about Clostridium species elsewhere in the article. If you're worried about G. stearothermophilus spores, then you're good, but this is about C. botulinum.

For what I understand (not being a specialist in the field, that is) the reason why G. stearothermophilus is quoted in the text is simply because it is an indicator of the quality of the sterilization process.
What I presum from this is that, if a sterilization process kills that, it kills all other forms of life.

https://en.wikipedia.org/wiki/Geobacillus_stearothermophilus
That's what I get from: " It is commonly used as a challenge organism for sterilization validation studies and periodic check of sterilization cycles. "

It's the iodine test of the sterilization procedure, that's what I get

That means the "initial study" indicated a very broad efficacity of the microwave oven against "everything", bacteria, viruses, and the spore used as the usual test for effective sterilization, again in my understanding.

I assume this spore is more resistant than other spores and that's why it is used as a challenge organism.

I would also like to stress that if 5 minutes are not enough, why not 10. Other means require much longer times and are much less certain in their results.

 

[bu_gee]

For what I understand (not being a specialist in the field, that is) the reason why G. stearothermophilus is quoted in the text is simply because it is an indicator of the quality of the sterilization process.
What I presum from this is that, if a sterilization process kills that, it kills all other forms of life.

https://en.wikipedia.org/wiki/Geobacillus_stearothermophilus
That's what I get from: " It is commonly used as a challenge organism for sterilization validation studies and periodic check of sterilization cycles. "

It's the iodine test of the sterilization procedure, that's what I get

That means the "initial study" indicated a very broad efficacity of the microwave oven against "everything", bacteria, viruses, and the spore used as the usual test for effective sterilization, again in my understanding.

I assume this spore is more resistant than other spores and that's why it is used as a challenge organism.

I would also like to stress that if 5 minutes are not enough, why not 10. Other means require much longer times and are much less certain in their results.

I took a brief look and I did find one article talking about G. stearothermophilus possibly being 20 times more heat resistant than C. botulini, but the article also indicates that there are two other analogs that are industrially used for this testing. The article itself specifically uses hyperbaric, heat sterilization in fats, so I don't know how that translates to home microwave ovens, but I, personally, would consider it precarious.

 

[Birrofilo]

I would like to make a broader reflection about C. botulinum.

Let's say that our kettle or our wort is contaminated with C. botulinum. Boiling the wort will kill the toxin if present, but might not kill the spore itself. That would mean, in principle, that our tap, kettle, pipes etc. are contaminated with C. botulinum.

That, again, should not worry us, because C. botulinum is dangerous only in a very narrow set of conditions (which is basically imperfectly canned food). I have never heard of a C. botulinum contamination through lack of hygiene in the kitchen, e.g. imperfectly cleaned knifes. It's not one of those nasty microbes which we can take in a sloppy restaurant or in our sloppy kitchen procedures.

We don't really need to know C. botulinum exists unless we want to make canned food that we want to eat "as is". And in that case, and only in that case, we should be extremely wary.

 

[bu_gee]

I would like to make a broader reflection about C. botulinum.

Let's say that our kettle or our wort is contaminated with C. botulinum. Boiling the wort will kill the toxin if present, but might not kill the spore itself. That would mean, in principle, that our tap, kettle, pipes etc. are contaminated with C. botulinum.

That, again, should not worry us, because C. botulinum is dangerous only in a very narrow set of conditions (which is basically imperfectly canned food). I have never heard of a C. botulinum contamination through lack of hygiene in the kitchen, e.g. imperfectly cleaned knifes. It's not one of those nasty microbes which we can take in a sloppy restaurant or in our sloppy kitchen procedures.

We don't really need to know C. botulinum exists unless we want to make canned food that we want to eat "as is". And in that case, and only in that case, we should be extremely wary.

Yes, and that has been my point all along. Oxygen is suffient to stop C. boltulinum spores from becoming active. Same for dehydration, acid, and ethanol. Note: I didn't add microwave to this list.

 

[Birrofilo]

I read the first part of the PDF you posted: very interesting!

What I get is along the same lines as before:

"
Since G. stearothermophilus is more heat resistant than any known
bacterial pathogen, thermal destruction of this non-pathogen surrogate should yield
validation data for rendering processing as a method of destroying pathogenic organisms
that may be inherent in raw animal tissues. The second part of this study is to determine
the suitability for using G. stearothermophilus as a general microbial surrogate for a
variety of uses in the rendering industry.
"

I did not read the second part, where the writer analyzes the suitability of this surrogate for this industrial purpose (the entire paper made me a little worried in any case, considering the possible migration of bacteria from dead animals to animal by-products used as animal feed, then to the fed animal, and later to the human feeding on that animal).

What I get is that, when G. stearothermophilus was quoted in the "initial study", it was quoted as an indicator of an effective sterilization procedure (however we define "sterilization", as in "good for Government work") and that it was inactivated by an ordinary microwave oven that we all can have at home.

This is quite extraordinary if we consider how impervious to sterilization is this particular microbe, 20 times more robust (heat resistant) than C. botulinum which is, itself, quite a champion of heat resistance.

As a side note, I point out that fats, in microwave ovens, reach a much higher temperature than water (which is limited by its boiling temperature of 100°C). Not that it be interesting to us homebrewers, but when we cook sausages, let's say, in a microwave oven that's not just a very fast way of cooking them, but also I suppose a "safer way", because the microwave heats the fat in the sausage much above 100°C and - but I have no way to "prove" it - probably higher than what would happen in the pan or on the barbecue (4-5 minutes completely cook 3 or 4 sausages in a MW oven, which means that a single sausage is cooked in 1-2 minutes).

I live it here as I think we have debated the point very much, it was very interesting and instructive, we don't have to agree on everything

 

[madscientist451]

Instead of canning the wort, why not freeze it?

 

[z-bob]

Instead of canning the wort, why not freeze it?

Oh, sure. Do it the easy way.

 

[Vale71]

Instead of canning the wort, why not freeze it?

Where are you going to put the steaks once your freezer is full of frozen wort? Properly canned preserves (in general, not just wort) have the advantage of room temperature storage.

 

[twd000]

if you drop the notion of bulk-processing, freezing wort makes sense. I don't need a full year's supply of starter wort; I only need enough starter for my next brew day. Just runoff a liter of wort from your kettle prior to the first hops addition, and store it in the freezer until the night before your next brew day. Take it out of the freezer and let it thaw at room temperature, then pitch yeast and your starter is off and running.

 

[marc1]

Instead of canning the wort, why not freeze it?

There's no room in the freezer because of all the hops

 

[bu_gee]

if you drop the notion of bulk-processing, freezing wort makes sense. I don't need a full year's supply of starter wort; I only need enough starter for my next brew day. Just runoff a liter of wort from your kettle prior to the first hops addition, and store it in the freezer until the night before your next brew day. Take it out of the freezer and let it thaw at room temperature, then pitch yeast and your starter is off and running.

A surprising amount of stuff can grow in the freezer, albeit at a very slow rate. Once everything is back at room temperature, they'll be the first ones to colonize.

 

[twd000]

A surprising amount of stuff can grow in the freezer, albeit at a very slow rate. Once everything is back at room temperature, they'll be the first ones to colonize.

where would those microorganisms come from in the first place? Runoff boiling wort into a container, Aussie no-chill style. Straight into the freezer with the cap on. Are you telling me an army of spoilage organisms would somehow breach the cap and invade and colonize my frozen block of wort? No chance .

 

[bu_gee]

where would those microorganisms come from in the first place? Runoff boiling wort into a container, Aussie no-chill style. Straight into the freezer with the cap on. Are you telling me an army of spoilage organisms would somehow breach the cap and invade and colonize my frozen block of wort? No chance .

Remember that what we're doing is steriliziation, which is defined as > 7 log10 reduction in microorganisms. We will never kill everything in the pot, only reduce it to the point where they can't overwhelm our preferred organism, presumably S. cerevisiae. You will be transferring it through the air to a santized container (which I believe is only 5 log10 reduction). It is still an appreciable opportunity of colonization. Also, breaching the cap is probably unnecessary as it will likely harbor the 5 log10 level of organisms as well.

You can't stop the organisms, only slow them down and knock back their progress. If you use it in a few weeks, you probably won't have a problem, depending on how careful you are. After 6 months, who knows?

The other option is to innoculate the wort with yeast and let them create an inhospitable environment for other organisms (acid+ethanol) before you freeze it. Then you just thaw and pitch.

 

[twd000]

but as soon as the wort thaws back to room temperature, I'm pitching yeast for my starter, which drops the pH to make it safe again

I'm comfortable storing frozen wort for months or even years if I forget about it in the freezer. There is simply nothing happening at those temperatures to make microorganisms multiply. Room temperature storage is a very different situation.

 

[Vale71]

where would those microorganisms come from in the first place? Runoff boiling wort into a container, Aussie no-chill style. Straight into the freezer with the cap on. Are you telling me an army of spoilage organisms would somehow breach the cap and invade and colonize my frozen block of wort? No chance .

Spores. They don't have to come from anywhere as they're already in the wort, 100% guaranteed. It's what we've been discussing in this thread all the time by the way.

Food in a freezer spoils, just very slowly. If you think you can store stuff there for years you might eventually find yourself going through the unpleasant experience of having your stomach pumped.

 

[bu_gee]

but as soon as the wort thaws back to room temperature, I'm pitching yeast for my starter, which drops the pH to make it safe again

I'm comfortable storing frozen wort for months or even years if I forget about it in the freezer. There is simply nothing happening at those temperatures to make microorganisms multiply. Room temperature storage is a very different situation.

Safe from what? If those organisms overwhelm your yeast before they can do their thing, they won't be able to create the "safe again" conditions. You can't go back in time to ungrow those organisms.

Here is a somewhat dumbed down (not because I think you're dumb, but because scholarly articles are hidden behind paywalls) and, honestly, mostly useless link to an article talking about Listeria growing at freezer temperatures.

 

[bracconiere]

Where are you going to put the steaks once your freezer is full of frozen wort?

aren't people supposed to have a dedicated freezer just for wort? supposed to have one for kegs of beer, one for fermenters, one for food, why not another for wort? doesn't seem like a stretch.....like if you feel like brewing but you don't have any empty kegs? you could just freeze the fermenter, then thaw it out for the yeast pitch?

 

[Vale71]

That kind of reasoning can get one lost deep into divorce territory...

 

[bu_gee]

[deleted]

Thought better of my comment.

 

[twd000]

Spores. They don't have to come from anywhere as they're already in the wort, 100% guaranteed. It's what we've been discussing in this thread all the time by the way.

Food in a freezer spoils, just very slowly. If you think you can store stuff there for years you might eventually find yourself going through the unpleasant experience of having your stomach pumped.

OK, "years" was a deliberate exaggeration on my part.

So I'll accept your premise that there are dormant botulism spores in my wort. I freeze the wort, so they never germinate and grow. I thaw the wort to room temperature and pitch yeast which rapidly drops pH into the safe zone. It's safe for the same reason making beer is safe. The freezer just hits the pause button between wort collection day, and yeast pitch day. There's nothing appreciably happening at -18C in the freezer.

 

[twd000]

Safe from what? If those organisms overwhelm your yeast before they can do their thing, they won't be able to create the "safe again" conditions. You can't go back in time to ungrow those organisms.

Here is a somewhat dumbed down (not because I think you're dumb, but because scholarly articles are hidden behind paywalls) and, honestly, mostly useless link to an article talking about Listeria growing at freezer temperatures.

you're right - that article is mostly useless

How about this link from the USDA? https://www.fsis.usda.gov/wps/wcm/c...rolling_LM_RTE_guideline_0912.pdf?MOD=AJPERES

PDF page 6 shows a table of conditions where listeria will not grow (though it may survive). Below 31.3 F there is no growth of listeria. So the amount of listeria prior to freezing is the same as the amount after thawing. I pitch my yeast and make my starter wort food-safe, for the same reasons every healthy fermentation of homebrew is safe.

 

[bu_gee]

I'm willing to accept that I don't trust my freezer to the level it deserves trust. That being said, my freezer routinely suffers both from user error as well as power company error, so I can't really make the case to trust it either. That is another discussion for another day.

 

[cmac62]

I like the idea of freezing a quart of my current wort for the starter for the next beer. Also, when coming to RT it will be oxygenated to some degree, and if I follow this will keep the spores at bay until I can pitch my yeast. Am I missing something, cause I REALLY am not a scientist.

 

[bu_gee]

I like the idea of freezing a quart of my current wort for the starter for the next beer. Also, when coming to RT it will be oxygenated to some degree, and if I follow this will keep the spores at bay until I can pitch my yeast. Am I missing something, cause I REALLY am not a scientist.

I'm sure we're all missing something. I only play a scientist on beer forums.

 

[z-bob]

I like the idea of freezing a quart of my current wort for the starter for the next beer. Also, when coming to RT it will be oxygenated to some degree, and if I follow this will keep the spores at bay until I can pitch my yeast. Am I missing something, cause I REALLY am not a scientist.

Your missing that you /can/ boil the frozen wort before pitching your yeast if you are really paranoid (there's not necessarily anything wrong with that) or are a belt-and-suspenders kind of guy. Although, that will deoxygenate it.

What kind of containers are you going to use in the freezer? Be careful with glass jars, they should be wide-mouth and tapered, and don't fill them all the way. I bought a bunch of polyethylene quart and pint togo cartons from a restaurant supply store and use them for freezer containers. They work great (although I haven't tried them for wort yet), and if I drop one out of the freezer it usually cracks but doesn't shatter, and they were cheap enough it's not a tragedy that I ruined one. The contents are still fine.

 

[cmac62]

Your missing that you /can/ boil the frozen wort before pitching your yeast if you are really paranoid (there's not necessarily anything wrong with that) or are a belt-and-suspenders kind of guy. Although, that will deoxygenate it.

What kind of containers are you going to use in the freezer? Be careful with glass jars, they should be wide-mouth and tapered, and don't fill them all the way. I bought a bunch of polyethylene quart and pint togo cartons from a restaurant supply store and use them for freezer containers. They work great (although I haven't tried them for wort yet), and if I drop one out of the freezer it usually cracks but doesn't shatter, and they were cheap enough it's not a tragedy that I ruined one. The contents are still fine.

Thanks for the reminder, I'll find something appropriate and safe.

 

[cmac62]

I'm sure we're all missing something. I only play a scientist on beer forums.

A few aces short of a deck LOL

 

[twd000]

Your missing that you /can/ boil the frozen wort before pitching your yeast if you are really paranoid (there's not necessarily anything wrong with that) or are a belt-and-suspenders kind of guy. Although, that will deoxygenate it.

What kind of containers are you going to use in the freezer? Be careful with glass jars, they should be wide-mouth and tapered, and don't fill them all the way. I bought a bunch of polyethylene quart and pint togo cartons from a restaurant supply store and use them for freezer containers. They work great (although I haven't tried them for wort yet), and if I drop one out of the freezer it usually cracks but doesn't shatter, and they were cheap enough it's not a tragedy that I ruined one. The contents are still fine.

I have a stainless steel growler that I received as a free gift from Williams Brewing

 

[Birrofilo]

Here is a somewhat dumbed down (not because I think you're dumb, but because scholarly articles are hidden behind paywalls) and, honestly, mostly useless link to an article talking about Listeria growing at freezer temperatures.

I find the asseveration in this article " Avoid drinking raw milk (milk that has not been pasteurized) or consuming foods that have unpasteurized milk in them. " quite daring.

Food which has unpasteurised milk in it is cheese. If cheese is allowed to season for a certain amount of time, use of unpasteurised milk is perfectly safe.

EU food norms are quite "anal" and they do allow unpasteurised milk in seasoned cheese. For certain "protected denomination of origin" cheeses, the use of raw milk (unpasteurised and "unthermized", proper raw milk as it comes out from the nipple of the cow) is for what I know mandatory, e.g.

Parmigiano Reggiano Dop
Grana Padano Dop
Fiore Sardo Dop
Fontina Dop
Caciocavallo Silano Dop
Strachitunt Dop (this is made "a munta calda", while the milk is still warm from the cow body temperature)
Castelmagno d'Alpeggio Dop

Emmentaler Dop (Switzerland)

And certainly many others.

There is no risk of foetus damage from eating superior quality cheese!

PS Consumers should be aware that imitations such as "Parmesan" sold in certain countries outside the EU is very distant in quality from properly made EU DOP cheeses, which are prepared according to a strict "production disciplinary".

PPS For what I know, seasoned cheese is the only case in the EU of admission of raw milk. In all other cases, raw milk must be heated during the transformation process.