Contamination Problems?

[BrewmanBeing]

Everyone seems really intense about contamination issues, but how huge of a deal is it really? When and how can beer become contaminated and what effect does it have? How can you tell if it is contaminated or not?

To clarify: It seems like if you make a yeast starter and get a quick, vigorous fermentation going, then the yeast are going to dominate and destroy any competing organisms that made it in. Once it has alcohol in it, it would seem like the alcohol itself would prevent any contamination from taking hold at that point.

 

[Brewsmith]

Well if you did this: https://www.homebrewtalk.com/showthread.php?t=14423 then you might have a problem. The problem is probably more than just your beer...

 

[Brewsmith]

Kidding aside, infection is most likely to happen before the wort is fermented. At that point there are tons of sugar that the bacteria is waiting to munch on. That is why it's so important that anything that touches the cooled wort be sanitized. Once fermentation gets going, the yeast out compete the bacteria and the hops and alcohol also prevent bacterial growth.

 

[BrewmanBeing]

Well if you did this: https://www.homebrewtalk.com/showthread.php?t=14423 then you might have a problem. The problem is probably more than just your beer...

Dude... That gives a whole new meaning to I"P"A.

 

[BrewmanBeing]

Kidding aside, infection is most likely to happen before the wort is fermented. At that point there are tons of sugar that the bacteria is waiting to munch on. That is why it's so important that anything that touches the cooled wort be sanitized. Once fermentation gets going, the yeast out compete the bacteria and the hops and alcohol also prevent bacterial growth.

So, basically it's mainly in the cooling phase before yeast has been pitched that one should be careful? How careful? Obviously, the fermentation vessel should be sanitized. Should the air within it be replaced somehow before filling it? Should I invest in a sterile aeration system? What difference in flavor would I get vs. just agitating the cool wort with whatever air happens to be in the carboy before/after pitching the yeast?

 

[Brewsmith]

You shouldn't need to go that far, unless you're brewing near a manure pile. There's no way to get all the bacteria out. That requires sterilization. We're just looking for sanitized, reducing the bacteria count to negligible levels.

 

[Truble]

that post is getting a lot of airtime!

As far as "conventional" sanitation, I have come to the conclusion that if you have not been affected by an infection, you wonder what the big deal is, and if you get bitten, you become very militant. I don't treat my brew day as a shift in the clean room, but I don't go that nuts. I sanitze with star san where needed, and keep it handy in a spray bottle for the brew process. I have a friend that was getting off flavors in batch after batch, and was near quitting, when he finally narrowed down the problem to his sanitation procedures-and he was WAAY more militant than me before and after.

I do treat prepared wort Very carefully, though, as that is the most vulnerable time.

Point is, you can be a maniac about it, laid back, whatever. Bleach, idophor, star san, whatever. Everyone has their favorite. Follow common sense.

 

[Dr Malt]

The other posts here point out that the most vulnerable time for contamination is at the cool wort stage before the yeast get going in fermentation. The outcome of contamination is generally an impact on flavor. Most contaminating bacteria cause an off flavor in the beer and, depending on the bacteria, the flavor varies. The most common flavor impact is a sour taste in the beer due to lactic acid produced by bacteria that metabolize sugars to lactic acid versus alcohol. Other off flavors that can come from bacteria are buttery (diacetyl, but this can also come from an incomplete fermentation), a phenolic or clove character when you didn't want it, or various off aromas. Often contaminated beer has a silky sheen or an oily surface appearance.

The alcohol production of yeast is not sufficient to halt the growth of all bacteria. Commercial breweries are haunted by a select group of bacterial species that are common contaminates in beer. As luck would have it, none of these bacteria are pathogenic (cause disease) but they can mess up the flavor of a good brew. That is, unless you are making a belgian beer, btu that's another story.

I hope this helps.

Dr Malt

 

[debtman7]

I've been wondering about all the sanitization paranoia too I mean, reading up on the history of beer, people made beer for thousands of years without even knowing that yeast was involved. I can't imagine that if ancient brewers had no knowledge of yeast or bacteria, that they really went out of the way to sanitize equipment. But then again I have no idea how often ancient brewers ended up with a skunked batch of beer...

So far all my batches have been good. But my wife's first attempt at wine turned into vinegar after we left it in the house while out of town for a weekend, with the A/C turned off..