End of reason, failure over failure

[arnaud]

Dear people, it is a time ago when i asked the same questions, but now i'm at the end of reason. More info is more doubt..
Summary;
About a decade ago i started with mead making; 10L water and 3kg Honey, added thea for tannine (pickwick claims this is not prsent in tea) but don't knwo where it was for, also lemon juice was mentioned)
So most of the time, honey and water, boiled it and scooped off the foam, let it cool and added yeast and covered it with a sheet(not sanitised or anything)and let it 'ópen fermentation' for 3 days.(this was to get it started)
after that in a 15L basket-bottle and in bottels after the fermentation is almost over, so it can produce bubbles in the bottle.
This went okay for a long time,(even when my 2 ferrets took a swim in the fresh must, it was an succes) and suddenly no more.

Some claimed it was to blame the open fermentation stage, the oxygen makes the yeast go sour. Others say it needs this stage, because LACK of oxygen makes the fermentation go sour.

So no one knows for a fact, and i tried a while without open fermentation, some of the batches turned out okay.

In advance of your questions, i used chloride solution(the supermarket stuff) for cleaning the bottels and pan.
i used sulphite once, some say it desinfects very well, others contradict.. again uncertainty about something what cannot be a question in today's science..

Despite very thoroughly rinsing out, nothing would yeast in that bottle again, so i threw that one out.
To today i do not understand why/how sulphite is used for cleaning.

I did NOT hydrate the yeast or make a starter; The first recipe i got, didn't mention it, and this worked many times(so not the cause of failure)
Also, to hydrate the yeast or make a starter, you need additional containers and things, which will additional risks of contamination..
Also, i do not understand the purpose of hydration in advance, there's plenty of (sterile!)water in the must?

The more thorougly i clean, the fouler the stuff gets.
at first i did not sanitize anything! and in the middle ages there were many brewerys!

So, chloride does obviously not do the trick, after using sulphite you can throw everything away.
What doen one use for cleaning???

As last, i live in a clean house.
my wife hast dust-allergy and i clean a lot!

 

[Medsen Fey]

Arnaud, I'm sorry to hear you are experiencing frustration. There are many variables that can affect the outcome of a fermentation. Obvious the yeast strain, and the nature of the honey, as well as temperature, pH, and other factors. Of course, anytime you deal with yeast, unexpected things can happen, but you can improve the odds for consistent outcomes if you follow the the same basic steps and develop a good routine. Keeping ferrets out also helps.

It might help us to know exactly what has gone wrong with your batches. You say they soured. Do you mean they developed vinegar odor? Are you having trouble getting them to finish fermentation, of just having trouble getting them to carbonate in the bottle? Which yeast strain are you using? Are you priming prior to bottling?

In general, the contamination risk is low. I still recommend good hygiene and sanitation practice, but with proper treatment, having containers for starters and rehydration do no pose an increased risk for spoilage. I have never seen a container that would not allow yeast to ferment in it so I cannot account for the bottle you disposed of. Cleaning does not cause things to go bad

There are many choices of sanitizer and I have used many of them. Bleach works but I don't want to use it in my area (a tropical swamp) because mold is too prevalent and Chlorine and mold make TCA which can spoil wine even if not in contact with it. I have used sulfite as a sanitizer many times without problems. I prefer using Iodophor or Star San as they do not require rinsing if used in proper strength, and that saves time.

Rehydration of the yeast does make a difference (see HERE for explanation). If rehydrated properly (preferably with GoFerm), the yeast take off faster, and ferment to completion more reliably. If you just sprinkle them in, most of the time they will work, but every so often you may find problems. By preparing the yeast properly, you will have improved consistency.

Providing aeration to the yeast is important to help them complete fermentation. Again, you can get away with not doing it sometimes, but doing it during the first 1/3 of fermentation will improve your chances to have complete fermentations.

Avoiding adding acid at the beginning is also a wise idea as that can impair the yeast by dropping the pH too low. You can add the acid once the yeast are done according to taste (you may find you don't need any - perhaps the sourness is too much acid being added in some cases).

Control the temperature. Cooler is usually better.

If you want carbonation, don't try to bottle at the end of fermentation. That can cause bottle bombs. You will be better off to let fermentation complete, then add a precise amount of honey or sugar to get the level of carbonation you want before bottling.

If you can tell us in more detail what has gone wrong with you batches, along with the specifics of what you did in each case, perhaps we can help to identify some alternatives to help.

Medsen (being very long winded again)

 

[YogiBearMead726]

First off, when you say that "this went ok for a long time...and suddenly no more", do you mean that you stopped being able to bottle carbonate, or that there is no fermentation happening whatsoever?

Most people here use one of two products for sanitizing; Iodophor or StarSans. These two products do not require any rinsing after application, just air drying. Bleach works ok for cleaning, but like you said, requires a lot of rinsing to get that smell out. And as to using sulfite to clean, I've never done/heard about that. Typically, people use sulfite to sterilize the must itself (more so when there are berries and other things in the primary that may have wild bacteria/yeast on them), not equipment.

As to your question about rehydration, it is an important step to ensuring that you get a strong, healthy colony of yeast that is well suited to survival in your must. And you don't really need a starter unless the yeast your using is known for being problematic or your starting gravity is way higher than most yeast could handle. Basically, you just need to rehydrate in something with some hot water. I use a coffee mug, since it's small (easy to sterilize) and heat insulating.

Your step about boiling the honey and scooping off the foam probably isn't the culprit for your lack of success, but this is a pretty dated step. Not only does it degrade the flavors and aromas of your honey (the stuff you scoop off/vaporize), but it's actually not a necessary step in sterilization. The must is pretty sterile on its own (as you saw first hand when your ferrets took a swim with no ill effects). Again, some people add some sulfite, but most have stopped boiling the honey.

Your open fermentation should be fine during the first day or so of fermentation. At the 1/3 sugar break, however, you'll want to put an airlock on your fermenter. This is the point where the yeast stop needing O2 to reproduce, and it starts to becoming a spoiler.

Also, what are you using to monitor the status of your batches? You really need a hydrometer to take measurements as the "appearance" of fermentation is a very poor indicator of what's actually going on.

For more answers/tips/advice to making this hobby a success, check out the "NewBee Guide" up on the left side of the page. It is worth reading all the way through, as it will go into more detail about things than we could here. It'll explain, as well, why to do certain things (like hydrating your yeast before pitching).

Good luck!

Edit: Medsen beat me to posting, so basically, ditto.

 

[mmclean]

People often use Sodium Metabisulphite as a steralizer.

2 oz of Sodium Metabisulphite to a gallon of water makes a solution a bit stronger than 1% and is more than enough to use as a no-rinse sanitizer.

 

[AToE]

Some of this just doesn't make sense to me, O2 doesn't make yeast go sour, neither does a lack of O2. Yeast need O2 at the beginning of fermentation in order to reproduce, this is just a fact. After fermentation is done, O2 can oxidize mead and damage the taste. I don't really see how there could be any debate with any of that, it's all science fact.

We really need a clearer explanation of what is going wrong with your meads, are they not fermenting at all, or tasting bad, or what?

From what you said above I don't see anything that should have killed your yeast entirely, unless the yeast was dead from the beginning. Rehydrating them properly would really be a good idea though, even if just tossing them in does work, it definitely kills a lot of them, so why not try to make more of them survive and rehydrate properly them first?

 

[AToE]

Ok, reading again (carefully, sorry the English is a little wonky to get used to! no worries though) it sounds like you are just getting terrible mead, possibly vinegar?

As to why to rehydrate the yeast, the full explanation is long, the short explanation is that when they're first absorbing liquid their cell walls are weak, and osmotic pressure from the sugar can make them explode. That's my not very good layman's explanation!

Secondly, there's really almost no way those santiizers you're using are causing your problem, unless you're not rinsing. Those santizers will not ruin your equipment, end of story - something else is going on.

Definitely please explain exactly what is wrong with your meads, if they are turning into vinegar, or what. Then we should be able to help you out.

(And yes, obviously you don't always need to santize things, it's a good idea, and if done properly won't do anything negative, but often you can be fine without it).

 

[fatbloke]

Also, where are you arnaud? as someone might be able to direct you to appropriate local supplies.

For sanitising, I use either 5 crushed campden tablets (NaCl) and 1 teaspoon of citric acid in 500ml of water. That is used in a spray bottle, and doesn't need rinsing. Or if you have powdered NaCl or KCl, then 10% solution is 100gm in 1litre of water.

regards

fatbloke

 

[arnaud]

Arnaud, I'm sorry to hear you are experiencing frustration. There are many variables that can affect the outcome of a fermentation. Obvious the yeast strain, and the nature of the honey, as well as temperature, pH, and other factors. Of course, anytime you deal with yeast, unexpected things can happen, but you can improve the odds for consistent outcomes if you follow the the same basic steps and develop a good routine. Keeping ferrets out also helps.

It might help us to know exactly what has gone wrong with your batches. You say they soured.yes, or moldly tasting. Do you mean they developed vinegar odor?yes! Are you having trouble getting them to finish fermentation, of just having trouble getting them to carbonate in the bottle? Which yeast strain are you using? Are you priming prior to bottling?Most of the time i use what is called here'superyeast'or champagne yeast

In general, the contamination risk is low. Then i wonder why this is happening..
I still recommend good hygiene and sanitation practice, but with proper treatment, having containers for starters and rehydration do no pose an increased risk for spoilage. I have never seen a container that would not allow yeast to ferment in it so I cannot account for the bottle you disposed of. Cleaning does not cause things to go bad
Maybe with sulphite it does.. i do not use platic cans, because debris will get stuck in the corners, only glass basket-bottels
There are many choices of sanitizer and I have used many of them. Bleach works but I don't want to use it in my area (a tropical swamp) because mold is too prevalent and Chlorine and mold make TCA which can spoil wine even if not in contact with it. I have used sulfite as a sanitizer many times without problems.Then, how many times do you have to rinse it before you can pour in the must??
I prefer using Iodophor or Star San as they do not require rinsing if used in proper strength, and that saves time.
Never heard of the stuff..

Rehydration of the yeast does make a difference (see HERE for explanation). If rehydrated properly (preferably with GoFerm), the yeast take off faster, and ferment to completion more reliably. If you just sprinkle them in, most of the time they will work, but every so often you may find problems. Like what, fouling of the must?By preparing the yeast properly, you will have improved consistency.

Providing aeration to the yeast is important to help them complete fermentation. Again, you can get away with not doing it sometimes, but doing it during the first 1/3 of fermentation will improve your chances to have complete fermentations.
Do you mean the necesaty to leave it ope to the air and risk even more contamination, (can the yeast 'get the oxygen out of the air??or add cold (contaminated??) tap water where oxygen is still in??

Avoiding adding acid at the beginning is also a wise idea as that can impair the yeast by dropping the pH too low. You can add the acid once the yeast are done according to taste (you may find you don't need any - perhaps the sourness is too much acid being added in some cases).
The lemon acid was for a sanitising or protection purpose.. no good expalnation of it.Control the temperature. Cooler is usually better.
Cool? yeast needs warm temperatures?? when cold nothing is happening because the yeast will die!!

If you want carbonation, don't try to bottle at the end of fermentation. That can cause bottle bombs. Never had that problem.. platsic soda bottles are very strong..You will be better off to let fermentation complete, then add a precise amount of honey or sugar to get the level of carbonation you want before bottling. And risk contamination again?? i do not understan how you manage to get good results?
If you can tell us in more detail what has gone wrong with you batches, along with the specifics of what you did in each case, perhaps we can help to identify some alternatives to help.

Medsen (being very long winded again)

I keep the process simple so there are less factors to contaminate.
if i did something different with the batches that went wrong, i would not do so the next time..

At the moment it is cold and the temperature in the living room is alternating very much(cold night) not very good for the yeast.
Our batroom is more temperature consisten, but is with the shower etc. a damp place, which may include bacteria.
is this not a good idea to keep the fermentation containers there??
I think contamination through the water lock is more at risk in this area??

 

[arnaud]

Also, where are you arnaud? as someone might be able to direct you to appropriate local supplies.

For sanitising, I use either 5 crushed campden tablets (NaCl) and 1 teaspoon of citric acid in 500ml of water. That is used in a spray bottle, and doesn't need rinsing. Or if you have powdered NaCl or KCl, then 10% solution is 100gm in 1litre of water.

regards

fatbloke

Hi, i'm living in the Netherlands..
the sulphite and citric acid, i read that it is to be used with hot water?? no one told me and i think it will go wrong with the glass bottles..

 

[arnaud]

Hi, also yoy thanks for responding!

Some of this just doesn't make sense to me, O2 doesn't make yeast go sour, neither does a lack of O2. Yeast need O2 at the beginning of fermentation in order to reproduce, this is just a fact. I don't understand any more, why do people say it and then why went very much batches with only boiled must(so no oxygen) directly under waterlock succeed?After fermentation is done, O2 can oxidize mead and damage the taste. You mean like sour wine the day after?I don't really see how there could be any debate with any of that, it's all science fact.

We really need a clearer explanation of what is going wrong with your meads, are they not fermenting at all, or tasting bad, or what?
The glass container i was stupid enough to clean with sulhite, was no longer able to let any fermentation happen, For the rest, fermentation started within 2-3 days, but the result is often verysour, or tasting like old socks might taste..

From what you said above I don't see anything that should have killed your yeast entirely, unless the yeast was dead from the beginning. How can you tell? it looks dry and stuff..Rehydrating them properly would really be a good idea though, even if just tossing them in does work, it definitely kills a lot of them, so why not try to make more of them survive and rehydrate properly them first?

Because, like i mentioned, rehydating needs additional containers and other things which are-drectly or indirectly- getting in to contact with the must. I cannot imagine that this is a good idea, since the way i use already goes wrong..

So, another stupid question; IF the yeast indeed needs oxygen(when does it and when doesn't??) can it get this from the added cold water or only from air?
i think air will give a bigger contamination risk??
Thanks everybody..

 

[akueck]

Yeast use oxygen to build their cell walls. The oxygen is needed to synthesize fatty chains that make up the bulk of the wall. It has been found that small amounts of oil (which are fatty chains) can be used instead of oxygen, though for homebrew scale operations the amount of oil is immeasurably small. [there are several threads where people tried oil, you can search for "olive" and probably find them.] Fermentations lacking oxygen can still be successful, though they will probably be slower and are more likely to stick (stop fermenting early). Adding more yeast can overcome this since they won't have to reproduce as much. Oxygen/no oxygen should not be directly related to a sour flavor.

Whipping in air is a pretty common practice. The risk of contamination is small: a healthy mead with a large yeast population and a generous alcohol content is enough to kill most organisms.

The sour flavor you're describing, can you tell us if it is like vinegar or perhaps a different kind of sour? Many people describe new mead as "sour". However, vinegar (acetic) smells and flavors do point to contamination. Other volatile acids can also be due to contamination, but are less common. Yeast do produce their own acids, which might be what you're tasting. Typically it takes at least a few months for a new mead to "pull itself together". If it makes you feel any better, I had a mead that tasted like socks for about 18 months, but now it is awesome--it just took some time to mellow out.

Contamination through your airlock is unlikely. The whole point of the airlock is to keep things out. Bacteria don't have feet, they can't crawl up the center tube, down the tube, into the container, and then into your mead. If you are still worried, use some cheap vodka in the airlock. That kills everything!

 

[Medsen Fey]

Arnaud, the point Akueck made is a good one. How old are the batches that you're having problems with? Many times, it takes 12-18 months for meads to work themselves out.

If you are having a problem with vinegar odor, that usually comes from having too much air in contact with the mead after fermentation is finished, which allows acetic acid bacteria and spoilage yeast to thrive. However, in your case it sounds like you are going straight into PET plastic bottles before fermentation is complete, yes? If so, then air exposure is not the problem. Akueck point out the reason oxygen exposure is needed during the early part of fermentation - typically during the first 1/3 of fermentation as measured by the hydrometer. After that point, keeping air away from the mead is a good idea. The best way to add air is not by adding water, but simply to open the fermenter and stir it around (gently so you don't get an eruption).

One thing that can cause many off odors is high temperature fermentation. Fermenting at cooler temperature (<21 C) is generally better. At higher temperatures, the fermentation goes faster, but it tends to produce sulfur odors (that may smell moldy) or fusel alcohols that may smell like Band-Aids and which taste very harsh. Champange yeast in particular are good at fermenting even down at 10 C. What you will find is that if you rehydrate the yeast properly, and pitch a large number of healthy yeast, the fermentation gets started faster even ithough the temperature is cool (though it still may take more than a day to see action).

One of the surest ways to prevent spoilage organisms from establishing a foothold in your mead is to pitch a large number of healthy yeast. They will then out-compete and supress the other organisms. This is another reason for proper rehydration. You will find that most of the folks on GotMead use rehydration, and many with a product like GoFerm that helps the yeast get started faster.

Another thing that may be causing problems for you is bottling with too much sediment. That can cause off odors and flavors. You may find that allowing your batches to finish and clear and racking off the sediment, then priming with more sugar and bottling may give you better results because there will be less yeast sediment in the bottles. And yes, bottle bombs aren't a concern if you use PET bottles.

Sulphite sanitizer is not a problem for wine yeast. I use the others because they are more powerful and faster, but sulphite works, and when I use sulphite, I don't rinse. I just pour it all out. A few drops of sulfite solution left in a 20 liter batch are irrelevant. They will not stop wine yeast.

It is also possible that the yeast strain you are using may cause odors, especially if not nourished properly. Are you using nutrients? If not, that can be a factor is stressed batches that cause odors.

You might want to visit the folks over at Brouwland, and try picking up another yeast such as Bioferm Champ or Kitzinger Champagne yeast to see it you get better results with one of them. They also carry iodorphor sanitizer, and some that are equivalent to Star San. If you aren't using a hydrometer, I'd get one of those as well. And nutrients if you haven't been using them (like nutrivit vinoferm).

If you sanitize, rehydrate the yeast properly, use nutrients, aerate during the first 1/3 of fermentation, keep the temperature below 21C, and rack it off the lees before priming and bottling, I expect you'll find your batches will turn out well on a consistent basis.

While you may be skeptical of this approach, and may be very concerned about contamination, I encourage you to suspend your disbelief long enough to try it out and see for yourself.

Medsen

 

[fatbloke]

Hi, i'm living in the Netherlands..
the sulphite and citric acid, i read that it is to be used with hot water?? no one told me and i think it will go wrong with the glass bottles..

Ah ha! Well it looks like Medsen Fey has directed you to a good place already, Brouwland is just "down the road" in Belgium (Beverlo, though how much of a drive it might be, I don't know, still, easier for you than me to get there ).

With sanitisation of glass, I just use soap and hot water (brushes, cloths, etc) until clean, then make sure that all soap residue is rinsed off with water, then just spray all surfaces that will come into contact with the mead/must/wine etc, with the sulphite/citric acid/water mix. I allow at least 3 minutes contact time, then any that has drained down is poured away and the glass container is ready for use.

Implements, like spoons, stirrers, hydrometers, test jars etc etc, are treated in the same way.

I always fit the airlock into the bung and then give the bottom of the bung that goes into the jar a spray as well. Plus I just put some of the sulphite/citric mixture into the airlock for the seal rather than plain water, and it doesn't evaporate as quickly as vodka can......

I can't see why it might be a problem putting the batches in the bathroom if it's likely to retain a more consistent temperature - other than family members complaining that they can't get into the bathroom for carboys/demi-john jars........

regards

fatbloke

p.s. Oh and when making the sanitiser liquid, crushed campden tablets and citric acid both dissolve easily in cold water. It doesn't need to be heated. I just put the correct amount of water into my spray bottle, then add the campden and acid, then give it a good shake up.

 

[arnaud]

everyone thanks for responding.
I will answer some of your questions and post some new questions which are raised within me.
First, yes all mead and other products (as strawberry wine made from lemonade) goes from the container, heved with a plastic hose(cleand with chloride AND boiling water) straight into bottles.
Most of the meades a made were good to drink a few weeks after botteling(time to get bubbly)
I like to get my mead semi-dry.. anything better but sweet
As for the process, i have a question.
After some failed batches, i eliminated the process where i hieved the must from one container to an other halfway(or by 3/4th) of the fermentation process, leaving the most of the residue behind.

As contamination was the reason i stopped this(in order to eliminate the chance of contamination, because of contact with;
1 plastic hose
2 other container
3 air which is in the container, and will take a long time to be pushed through the waterlock while the fermentation process is quite slow.

But i cannot help to think.. The must staying all of the fermentation process in the same container; can the residue (old/dead yeast?) be a cause?

And yes, i use yeast nutrients and the last 2 batches i added vitamine B1 tablet.

As for the hydratation of the yeast, last weel i tried it. The process started really going at the beginning of the 3rd day, that is With hydrated yeast (left for 2 days in a can) AND open yeasting.
So this does not seem to give an advantage, since adding dry yeast directly in the must under waterlock gives the same result in the same time.. so i don't have the expreience that hydrating gives a better start

okay, yeast needs oxygen, but how could it grasp it out of the air?
Last batch, now under waterlock i added cold water so oxygen is present when adding the boiled down must.

Also, i read an answer that some are making mead without boiling??
1 how do you sterilize the must?
2 since boiling breaks the sugars, can not-boiled must become a semi-dry mead?
3 how do you sterilize cold tap water??when you boil it all the oxygen will be gone!
Y.S
Arnaud

 

[Medsen Fey]

After some failed batches, i eliminated the process where i hieved the must from one container to an other halfway(or by 3/4th) of the fermentation process, leaving the most of the residue behind...

But i cannot help to think.. The must staying all of the fermentation process in the same container; can the residue (old/dead yeast?) be a cause?

If mead sits on a large amount of lees for a long period, it can sometimes pick up off odors/flavors and sulfur odors.

As for the hydratation of the yeast, last weel i tried it. The process started really going at the beginning of the 3rd day, that is With hydrated yeast (left for 2 days in a can) AND open yeasting.
So this does not seem to give an advantage, since adding dry yeast directly in the must under waterlock gives the same result in the same time.. so i don't have the expreience that hydrating gives a better start

I (and others) have found that rehydrating properly, especially using a product like GoFerm shortens the time until activity is noted. This has been shown in scientific wine studies and my experience certainly is consistent with this.

Perhaps you can describe your rehydration process in more detail?

okay, yeast needs oxygen, but how could it grasp it out of the air?

If you open the container, air (with oxygen) will go into the space in the container. Since there is no oxygen in the solution, the oxygen will be rapidly absorbed by the must. If you stir or swirl it around, the oxygen pick up will occur quickly.

Also, i read an answer that some are making mead without boiling??
1 how do you sterilize the must?
2 since boiling breaks the sugars, can not-boiled must become a semi-dry mead?
3 how do you sterilize cold tap water??when you boil it all the oxygen will be gone!

Yes I do not boil my musts. That would chase off many aromatic compounds.
1. A must does not need to be sterilized. In properly cured honey, nothing will grow and the only thing you will find are some spores. When you dilute the honey and pitch in active wine yeast, they will dominate the fermentation. Unless you are adding a lot of fruit that may have yeast/bacteria, there is little concern. In the case where I do want to treat the fruit, I will add potassium metabisulfite ( about 1 Campden tablet - roughly 440 mg - to each gallon )
2. The sugars in honey are virtually all simple (glucose and fructose). Boiling does nothing but cause caramelization which you may not want.
3. I don't sterilize it. I typically use bottled spring water, or filtered water.

 

[Chevette Girl]

For sanitising, I use either 5 crushed campden tablets (NaCl) and 1 teaspoon of citric acid in 500ml of water. That is used in a spray bottle, and doesn't need rinsing. Or if you have powdered NaCl or KCl, then 10% solution is 100gm in 1litre of water.

Just a clarification, campden tablets are not NaCl, that would be table salt... they are generally either potassium or sodium metabisulphite.

It's OK to use potassium metabisulphite on your equipment without rinsing because the amount that ends up in the must will be so dilute it won't bother the yeast, and it also loses its effectiveness in a must after 24 hours even at the strength you use campden tablets to sterilize your must (1 tablet per gallon).

Your concerns about contamination by introducing other vessels and equipment during rehydration and racking from one carboy to another are unfounded if you get into the habit of sanitizing everything that touches your must.

If you are concerned about the water you are using, you can either treat it with 1 campden tablet per gallon 24 hours before you add the yeast (you can use campden tabs before or after you add the honey, if you're concerned about contaminated honey this might be the way to go for you) or boil just the water and cool it before adding the honey.

And yes, yeast can get oxygen out of the air during your open fermentation but it's more effective to add oxygen for the first couple of days by splashing it around with a spoon or whisking it to make bubbles, again, if you've sanitized the spoon or the whisk, you won't be contaminating your must.

Hope this helps!

 

[arnaud]

hi, update, tried to sterilize the (new, don't want re-contamination)glass containers (15 litre) with a blow torch, didn't work out good.
Wonder how to do it effectively an other way.

 

[AToE]

I still seriously doubt that contamination is your problem with these, something else has to be going on - but the language barrier is sadly making this very difficult to diagnose, and it's a very tricky one to diagnose because from your description of the problem plus everything you've tried that hasn't work does indeed sound like contamination to me - but it just doesn't seem possible considering the lengths you've gone through to sanitize everything.

Sanitation simply does not have to be this thorough, the risk of contamination is extremely small. I routinely mess up my sanitation and have never had a problem, I've stuck my whole arm in the mead and had no problem, I've had meads sit open for hours at a time with no problem, heck, you even had a ferritt take a bath in your old batch and it was fine!

I really wish that we could help you more with this, it's driving me nuts not being able to help you better.