off flavors and sanitizing/scratched plastic

I've read through the various posts here and the common wisdom is that off flavors are because of poor sanitizing or using scratched plastic carboys/buckets. I'd like to read from some of the "master brewers" here and get their take on this commonly held notion.

Here is the basis for my question:

  1. Palmer's reference has very few off flavors that he mentions as a function of cleaning and none from using scratched fermenters. So, if you know that you are using proper sanitizing technique, have you still produced off flavors? If so, were you able to track down the source as something different than Palmer's observations?
  2. Another commonly held notion is that glass is better than plastic because plastic scratches and these become sources of infection and off flavors. Have you ever had this happen with scratched plastic carboys when you knew that you sanitized properly at the beginning?

Topic plastic glass off-flavor sanitation homebrew

Category Mac

1
answered at

Off flavors come from process issues and sanitation issues. An example of a process issue would be over-pitching or under-pitching yeast, or over oxygenating or splashing while transferring and oxidizing finished beer. Sanitation issues are off flavors from microbial infection. I would say that most of the time off flavors are generated through process issues, not sanitation issues. That is to say, its not hard to have good sanitation practices.

Knowing how to distinguish where an off flavor came from is very important. I think this is why you don't outright see Palmer's book talking about scratched fermentors. He talks about where the flavors come from. (You can get microbial infections without scratches)

That said, scratches don't guarantee microbial contamination. I understand the theories behind it, but I can't say know of too many failed batches that can be tracked to a scratched fermentor. I think the scratch thing is a bit overplayed. A deep gouge that you just can't clean out effective would give you problems. Scratches only become sources of infection if you had an infection in the last batch.

1
answered at

I can't comment on Palmer's observations, I haven't had a plastics-related infection.

Generally, from a scratch standpoint glass is better than plastic, when it comes to using carboys as fermenters. But only from that standpoint. Plastic carboys are superior in a lot of ways, but hard to clean because you can't just go at them with a bottle brush.

Personally, I think a carboy is sub-optimal to ferment in. Age? Sure. Ferment something that doesn't krausen? Sure. But regular old beer? No.

I find plastic buckets are superior. Easier to clean, easier to handle and not slippery and dangerous like glass carboys. Soft cloth and mild soapy water to clean. Never store anything but beer in them, no matter how handy it would be to just slip your bottle capper into the bucket.

Small scratches can harbor bacteria. I'm not saying that Palmer is wrong, but I think there is anecdotal evidence to support the idea.

Here are a couple of related links to plastics on this site.

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