I'm going to add some fruits (oranges) during secondary fermentation and worried about the risk of contaminating the beer. What can I do to prevent contamination?
For my fruited sours I have done (kettle sours), I have simply just pasteurized my fruit. When I used a bunch of fresh mangos in my last one, once pureed and ready to be added into the keg, I raised the temp to around 150F and held that temp for around 5 minutes. That time/temp is considered a 7D level pasteurization, or only 1 cell in 10,000,000 might survive. You could use lower temps for longer periods of time, say 145F for 14 minutes, 140F for 35 minutes… I then dumped right into the keg and racked the beer on all the fruit puree. Great results with my fruited beers this way and the held bright fruit flavors, while eliminating any contamination risk (even though it’s fairly low due to the pH and such of the finished beer). But still, better safe than sorry! If using whole fruit like that, I would probably just drop them in some star-san whole to 'clean' the outside of the fruit. Then cut open and add into the fermenter. At least you can clean/sterilize the dirty portion of the fruit (outside).
I find heating fruits tends to take away flavors so you have to use more fruit. My personal preference is to buy frozen fruits, puree, and toss them in without worrying about it. Never had a problem doing that but there is some contamination risk. If I'm using fresh fruit I tend to be a little more cautious so I add a campden tablet while pureeing them and let it sit for 24 hours. I will also freeze and thaw them first to get maximum flavor out of the fruit. This way also takes a lot less effort so that's the biggest reason I go this route of pasteurizing. Lots of ways to go about this and you'll have to find what works for you. For oranges I would zest the orange and soak it in some vodka.
I've used blue berries, mangos and raspberries, all fresh and all get mashed then brought to a boil then dumped into the secondary. I seem to get good flavor. Never used oranges.
Thank you for your answer! Just curious though, if you pasteurize the fresh fruit puree with heat, wouldn't it taste cooked and kinda off? Or does it yield just about the same flavor after the fermentation process?
No worries adding the fruit as is. Gently scrub clean the rind with a brush. Process in a clean and sanitary manner ... and it's all good. That and beer is acidic ... so there's minimal risk.
Invertalon pretty much gave an exact answer. But just to be clear, you can contaminate your beer in other ways too. I actually wrote a post about this on my blog if you want some tips to avoid contamination of your beer in general Good luck brewing
