Removing most of the yeast, and adding some priming sugar is when the flavours go bad for me.
This is what really stands out for me...Just WTF are you talking about????
What do you mean by removing most of the yeast? How are you doing it? and more importantly
Why are you doing it?
Unless this is your phraseology for racking to your bottling bucket, then you are doing something that is not common for us homebrewers to do...And however you are doing it, may be the problem.
I'm going to post what I wrote in the other thread here, in case you didn't see it.
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Have you ever actually taken your beer to another homebrewer or homebrew shop to confirm your "infection?" A lot of brewers misdiagnose green beers as infection...A lot of new brewers misdiagnose their beers as just about every pathology/problem they read about...DMS, Diactyl, etc, when in reality it is simply a young beer...
Because honestly....it is a very difficult thing to do...infections are really not that common if you follow basic sanitization practices. And if you do get an infection then it is a good idea to flush everything with bleach water, replace any hoses, and make sure there are no scratches in buckets, etc.
Let's start with some basic science to show you what I mean.
First no known pathogen can grow in wort/beer...It may get moldy but it wouldn't make you ill.
Besides even the smallest amount of viable yeast cells would start some fermentation which would be helping to prevent anything from growing. Don't forget, that
hops are a preservative to begin with...
Googling "pathogens in wort/beer" netted me this info from a food microbiologist/homebrewer on another forum...
Can you get a PATHOGEN from beer. No. NO *NO* Did I make that clear? You have a ZERO chance of pathogens in beer, wine, distilled beverages. PERIOD!
Pathogens are described as organisms that are harmful and potentially life threatening to humans. These are some 1400+ known species overall encompasing viruses, bacteria, fungi, protozoa, and helminths. Of that group, we are only interested in those that can be foodborne. Quite simply, if it can't survive in food, it isn't in beer. That knocks out all but bacteria and fungi. Viruses need very specific circumstances to be passed around... like on the lip of a glass or bottle, not the beer in it. **Ahhh...CHOOO!**
Pathogens as a rule are very fastidious beasts. Meaning that they want very specific temperatures, acidity, nutrients and other conditions to thrive.
Bacteria that *could* live in wort, cannot survive even a little bit of fermentation. There are several reasons for this. One is in the 'magic' of hops. It is the isomerized alpha acids that provide a preservative effect to the beer, which happens to inhibit pathogens! Good deal for fresh wort!
Another reason is the drop in pH from fermentation. Next, yeast emit their own enzymes and byproducts, all in an effort to make the environment hostile to other creatures. The major one is alcohol, of course, but their enzymes will break down less vigorous organisms and they become sources of trace nutrition. Now the latter is very minor compared to the effect of alcohol, but it exists! Most of the time these enzymes work on the wort, not organisms until late in the process. Good deal for beer! ...uh, wine too.
Oh, Botulism specifically... did you know that this is an anaerobic pathogen? It's toxin is one of the few that is broken down by boiling. Did you know tht it is strongly inhibited by isomerized alpha acids, even in water? Since fresh wort has a healthy amount of oxygen in it, the beastie cannot even get started, then once the O2 is used up, it doesn't have a chance against the hops or the yeast.
All that is left are a handful of acid producing bacteria that'll ruin a batch of beer. Overall, there are less than 200 organisms that can survive in beer and lend flavor effects. None of these for very long, or very often. Lambic being the sole exception, and if pathogens *could* survive, that'd be the style where you find 'em.
So, you might make a beer that'll kill your ego, but not your friends, family, co-workers or enemies.
Repeat after me
Hops Are Our Friends!!!
Now let's talk boiling...If you've boiled your wort, then you have effectively steralized it...If you've cooled quickly when you put you wort into a
sanitized you've reduced the number of infection producing entities greatly.
Fermentation as mentioned above will further kill off more nasties...
CO2...the cushion of co2 produced during fermentaion, does just that cushions the surface of the beer from most airborn particulate matter that could infect the beer...and the slight up/out draft of the co2 pushing away the O2 narrows the odds of it happenning.
Next let's talk sanitizers...If you are using a FDA approved sanitizer (Iodaphor, or Starsan). In order to get FDA approval to use the name sanitizer it must meet the following standard.
The official definition (Association of Official Analytical Chemists) of sanitizing for food product contact surfaces is a process which reduces the contamination level by 99.999% (5 logs) in 30 sec.
These sanitizers
must be active against bacteria, viruses, yeasts, molds, fungi, and protozoans.
(there's some good info on using sanitizers here...including the link to the basic breweing podcasts about iodophor/starsan and bleach (the same episode as starsan.)
https://www.homebrewtalk.com/showthread.php?t=54932
This doesn't even take into consideration the mere antibacterial action of soap and hot water during our cleaning.
So what I am saying is...Each step in the chain of cleanliness/sanitization
greatly reduces the possibility of infections...add to that the very chemical/ph composition of the beer and it's inability for Pathogens, greatly reduces just what could grow in it....
So if there's 200 types of entities that could possibly survive in beer...and a
Sanitizer is more than likely killing 99.999% of them in a mere 30 seconds of contact....Can you see how the odds are in our favor???
If your beer is infected then you should be able to easily wipe it out with what I mentioned in the top of this long post....If you truly got it once, you could pretty easily nip it in the bud by running bleach water in most things, replacing anything scratched, replacing your hoses, and make sure you are using a strong
no-rinse sanitizer.
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So I'm really wondering about this "removing yeast" business....
Or like you seem to have said, you need to boil, boil boil....which isn't a bad thing to do.
What does your infected beers taste/smell like? Vinegar? If we can isolate the nature of it we may be able to figure more out.
You may find this article useful as well..."Basic Elements of Equipment Cleaning and Sanitizing in Food Processing and Handling Operations"
http://edis.ifas.ufl.edu/FS077 It's got some good stuff in it.
(Sorry for the length and the repitition some of this is not in here so much for you paul, but for the nervous lurkers who think the mere looking at their beer will infect it. If paul did get infected then it is a rarity, and we are working diligently to problem solve it
)