Cider Started Fermenting Again after 2 Months

[LoudounBrew]

Have an apfelwein in a secondary. Just noticed to tonight that it has started fermenting again. Initial fermentation stopped in mid-December. I transferred to a secondary around the new year, so it's been in the secondary for a month and a half.

There's practically no head space, and I cleaned and sanitized the carboy about as well as you can.

Any thoughts beside it being an infection.

Thanks.

 

[oljimmy]

Loudoun, could it not be malo-lactic fermentation? That fits your description perfectly, timing and everything. One way to tell is that MLF bubbles are often (not always) larger and slower-moving than the smaller bubbles thrown up by primary fermentation. What does it look like?

 

[schwiz]

Do malo-lactic fermentations create more alcohol?

 

[oljimmy]

Hey schwitz: no, they primarily convert malic acid into lactic acid. Lactic acid is softer and has a more "buttery" taste, so the overall effect is to reduce the acidic taste and 'round' out the cider. Much depends, though, on just which strain of bacteria is doing the conversion... and unless you introduce a strain yourself, it's impossible to know what's happened until you taste it!

 

[LoudounBrew]

oljimmy,

Thanks. I never thought about malolactic fermentation. The juice that I used was store-bought and pasteurized, but it was pure pressed apple juice with no other additive. Also, I did add malic acid to the juice to give the finished product a bit more tartness, so there was definitely something for the LAB to chew on. I guess that I thought that you had to add LAB to the cider to get MAF.

While I'm not a bubble expert, they do look a bit bigger than what I remember.

I know that MAF tends to smooth out the flavor of the acid, converting it from malic to lactic. But does natural LAB lead to off flavors?

 

[oljimmy]

Yeah, it's a bit odd that pasteurized juice would undergo MLF, though as I understand it some of those strains are super-hardy, and cider is very friendly to MLF, so even if pasteurization killed 99.99% of them they might still start up again eventually. Maybe?

Another thing is that MLF bacteria are very common features of a home environment. Lots of the cultures are in ordinary dairy products, for example. So, even just exposing the juice to the air during the initial stages could (possibly) result in the introduction of cultures.

This is all total speculation, though. You very well could have some residual sugars which are being eaten by zombie yeast, ha ha. But that would be very strange, given that fermentation had stopped 2 weeks before you racked.

 

[LoudounBrew]

Well, I've certainly spilled my share of apple juice on the floor of my brew room in my basement. I try to clean it up, but I wouldn't be surprised if I missed some. I suppose that LAB could have latched onto that and become more prevalent in the room. Don't know.

To avoid this issue in the future, is it good procedure to either add some sulfites to cider after fermentation (probably when I rack to secondary) to make sure everything is dead? Or I suppose, I could add some LAB to get MAL from the right bacteria. Again, I like to add malic acid to the juice, so I'll always have a fair amount of food for LAB - domesticated or wild.

Thanks.

 

[LoudounBrew]

Beginning to wonder if this is malolactic fermentation. The juice/cider is cloudy. From my little bit of reading, it doesn't sound like MLF causes the cider to turn cloudy, but I could be wrong.

If it's not MLF, I can't imagine what's going on. The cider/apfelwein fermented to point where there wasn't any sugar left, so what would a yeast be eating.

 

[EpicCider]

Malo-lactic fermentation is a good thing for a better taste. I feel like I should be saying congrats.