When are you most susceptible to infection??

Hey all,
Brand new member posting here. I was spurred to join bc I lurk on these forums all the time and finally have an issue coupled with a broader question that I'm losing sleep over so please placate a brother here.
First of all, I just did my 2nd all grain batch - a citrusy saison. Brew day went great and I put her in the carboy, put that in my swamp cooler and attached my blow off tube. Then, bc the room is pretty bright, I draped a blanket over the whole thing just to keep it dark. Well, true to saison yeast, the fermentation got pretty wild and blew off the blow off tube overnight, so the blanket was just resting on top of the open carboy. When I checked it in the morning, there was a small circle of krausen crud where the blanket rest on it and some more crud leaked over the side. I resanitized the tube and put it back on, but I fear that a blanket is just a harborer of bacteria and I may end up with an infection. How susceptible am I at this point?
The larger question I have is when is a brew most susceptible to infection? Is it during the cool down, during fermentation, post fermentation, bottling? Or is there pretty much an equal chance throughout the brew?

Your beer's most vulnerable period is, for the most part, from when it has been cooled in the kettle to when it was had its yeast pitched and airlock/blowoff attached. From that point on, the the chance of infection decreases more each day; initially, an appropriately sized pitch of yeast should outcompete most other organisms, and once fermentation has begun, the ethanol produced during fermentation will make the beer a very hostile environment for bugs and nasties.

When it comes to your situation, I wouldn't stress to much; positive pressure created inside the carboy by the CO2 will do an admirable job of keeping most of the crap out, and the crap that does get in will be received by an army of yeast and a toxic environment. No stress -- RDWHAHB!

I wouldn't worry about it but in general the further along fermentation is the less vulnerable it becomes.

Thanks for the responses. Good info guys. I have always wondered why infection is at its most vulnerable point where the yeast can be near it and will be reproducing the most. Is this just due to the yeast coming into contact with bacteria, mutating (or whatever would happen), and then reproducing as this mutated strain? What exactly is going - on the microbiology end - in an infection?

I find myself most vulnerable to an infection when my immune system is depressed. This can happen for a number of reasons, such as stress, depression, HIV, marriage/childbearing, cold weather, and possibly death.



As far as the microbiological mechanics of it, yeast usually grow fast enough to outcompete most other microorganisms, especially when you pitch a lot of them into your wort. If you have a "large enough" population of a spoiling yeast or bacteria, it will compete with the yeast. Since these bugs aren't really optimized for brewing tasty beer, you get off flavors and aromas (but nothing that'll get you sick). In addition, yeast doesn't ferment everything in the wort, so there is the possibility that something else can "take over" where the yeast left off. You won't be getting any mad scientist yeast/bacteria hybrids, though.

Yeast and other organisms (bugs) are all competing for the same resources. If the yeast gets a head start there is less resources for the other bugs to multiply. Also in the case of beer the further along fermentation gets the higher the more alchohol and many bugs are not tolerant to alchohol further limiting growth.

Also keep in mind that there was a reason the blow off tube...well...blew off! There is an vast amount of C02 produced in the beginning states of fermentation. That positive pressure in your carboy will push away anything that even gets close to your beer!

RDWHAHB...any nasties that were on the blanket don't run back to the fermenting beer...they don't move like ants AFAIK.