to shake or not to shake

[TipsyDragon]

i know this is normal so I'm not even remotely worried. i am making a blueberry melomel and this past Saturday i racked my 5 gallons of mead onto 6lb. of blueberry puree with a teaspoon of pectic enzyme. there was evidence of renewed fermentation within minutes of racking and placing of airlock. when i was racking i simultaneously poured dry ice fog into the secondary effectively filling it with CO2. this coupled with the CO2 put out by the now fermenting yeast has filled my headspace with plenty of CO2 gas. now, this morning i checked on things and there was a fairly thick layer of blueberries floating at the top of the carboy. i know this is normal because the yeast are eating the sugar and producing CO2 and making the blueberries float.

my question is, should i shake the carboy and make the mat of blueberries sink back down to the bottom or just let it be? i can't see why shaking would be a bad thing. what do you guys think?

 

[Yooper]

I wouldn't shake it, unless the floating "cap" of berries is drying out on top.

You don't want the fruit to dry out.

 

[fatbloke]

I wouldn't shake it, unless the floating "cap" of berries is drying out on top.

You don't want the fruit to dry out.

Ah! whereas I'd be gently swirling it as you want to keep the fruit in contact with the yeast cells as much as possible. I find that way, the pulp/cap eventually sinks with the rest of the lees......

S'up to you.....

 

[gratus fermentatio]

+ 1 on the gentle swirl, too rough & it could cause it to foam up considerably.

 

[malkore]

or use a spoon to punch the fruit back down in.
otherwise be REAL gentle on swirling the carboy

 

[TipsyDragon]

or use a spoon to punch the fruit back down in.
otherwise be REAL gentle on swirling the carboy

problem with that is that it runs the risk of contamination from opening the carboy then jabbing it with a spoon. besides i don't have a spoon small enough to fit through the neck of the carboy or with a long enough handle to reach the fruit.

as far as being gentle when swirling i don't see why. the head space is totally full of CO2 so its not like i'm going to oxidize it.

 

[Androshen]

If you are using a Better Bottle carboy, I saw a video online about the best way to swirl one ....
You place a ball in the recess under the carboy and then simply "roll" the carboy in a rotating fashion on the ball.
It was all pretty slick .......

"Swirling the contents of a Better-Bottle carboy vigorously requires almost no effort, if a tennis ball is placed in the punt space under the carboy. Do not tilt the carboy by so much that the edge of the carboy's base touches the surface (see Important Note). And perform the swirling on a smooth or soft surface for good measure. Leave extra head space during initial mixing and aeration to maximize agitation. Tune your swirling motion for the desired effect; very hard swirling may result in less efficient mixing than more gentle swirling.

Important Note: Never rock or swirl Better-Bottle carboys without using a tennis ball. Doing so will cause the edges of the bottom of the carboy to flex under great stress repeatedly and eventually cause cracks, like bending a paper clip back and forth. "

 

[TipsyDragon]

thanks for the info but i don't use BBs, don't like the idea of an acidic mead sitting in plastic for several months. i'm using a 6.5 gallon glass carboy.

 

[fatbloke]

problem with that is that it runs the risk of contamination from opening the carboy then jabbing it with a spoon. besides i don't have a spoon small enough to fit through the neck of the carboy or with a long enough handle to reach the fruit.

Well the handle of a plastic stirring paddle would do the job just as easily. If you've sanitised it, it's possible, though unlikely, that you'll introduce spoilage organisms (see below)

as far as being gentle when swirling i don't see why. the head space is totally full of CO2 so its not like i'm going to oxidize it.

Ok, so on the face of it, that'd make sense, but it's about meads (and other alcoholic brews for that matter) and the way that CO2 which is currently in solution in the ferment, is released.

Imagine you've shaken the hell out of a bottle of coke or something carbonated like that, but then put it back in the fridge for a couple of hours.

When you come to open it, it starts to fizz/foam, but there's a slight delay before it goes batsh1t and erupts out of the top.

It can be (not necessarily) similar with a ferment, you can give it a gentle swirl and the movement is enough to re-incorporate the fruit into the liquid part, without causing mead fountains. While you could easily be just a little bit less gentle and it's enough to cause the CO2 to come out of solution and foam like hell, coming out the top or through the airlock etc.

You've already shown that you're thinking on the right lines by questioning the use of a spoon/paddle/whatever and the potential for introducing spoilage organisms, which it a good way to be thinking (though you'd still be in the same position when racking/syphoning/bottling etc.... see where I'm going ???), so why not just be gentle with the ferment and swirl it enough just to mix the fruit back in. The idea of the tennis ball trick from BB is just as valid with glass, not that you're likely to get stress cracks but the weight on the tennis ball will allow enough clearance for you to be able to swirl the carboy in a circular motion enough to get the fruit pulp moving back into the liquid, as it should disturb enough of the CO2 in the fermenting part of the fruit to allow it to sink again - the CO2 coming out, as usual through the airlock.

Don't forget, CO2 is (apparently) a "heavier than air" gas, so unless you're racking from one container to another (enclosed containers that is), either the active fermenting part or the natural de-gas of a finished ferment, is going to continue to produce CO2 just on top of the liquid providing a CO2 rich blanket of gas. It's the same reason why you'd normally reduce the airspaces in secondary or finished ferments. We don't have a chemical laboratory in our back pocket, so there's practically no way of measuring the CO2 content of the gas layer. It's just to be on the safe side.

Besides, meads and honey based ferments seem to be more resistant to oxidation than "normal" wines..... I think it's something to do with the properties of the honey........

good luck with the brew....

regards

fatbloke

 

[TipsyDragon]

while i do appreciate your advice there are a few flaws in your logic.

the reason the soda bottle gushes after shaking is because there is more than 1 atmosphere of CO2 dissolved in solution and the shaking releases it. during fermentation any CO2 above 1 atmosphere is released into the headspace of the carboy and pushes out the airlock equalizing the pressure.

i know the head space is completely full of CO2 because when i was racking i filled the headspace with dry ice fog which is almost totally CO2 then applied an airlock. so the CO2 can get out but no outside air can get back in. Also when i added the fruit the yeast that was in suspension in the mead began eating the sugars from the blueberries and began fermentation again, producing more CO2. the airlock is bubbling ever so often releasing pressure.

the rather inventive and cool BB/tennis ball idea works because of the indentation in the bottom of the BB. it prevents the ball from rolling/sliding out from under the bottle while swirling. a glass carboy has a flat or almost flat bottom. i would be to afraid the ball would just slide or roll out from under the bottle.

 

[Yooper]

The co2 might be there during fermentation, but it does disapate with time- that's why it's so important to top off your mead during secondary. Sure, it's heavier than air but the laws of diffusion apply. The co2 will work its way out, and that's why you don't generally have to degas meads that have been aged for a bit.

Think about it. Trees produce co2. But there isn't a "blanket of co2" around them indefinitely. The co2 diffuses into air around it, due to the laws of physics. It will search for equilibrium.

In a short period of time, it'll be ok. But it's a fallacy to say that there will be a thick blanket over the fermented liquid long term. Shaking it will force it out sooner, rather than later.

If you fog the mead with co2, that will help prevent oxidation. But it won't last indefinitely.

When I make wines, I stir the cap down to keep the fruit from drying out on top. I don't see any other benefit to stirring/shaking though. The yeast know where the sugar is.

 

[TipsyDragon]

first, trees produce O2 not CO2..

second, if the head space is totally filled with CO2 and no air can get back in from the outside how is it going to diffuse?

but i do agree, once the fruit cap is knocked back down there isn't much point in shaking.

 

[wayneb]

Couple of points of clarification are needed here.

First, trees produce both CO2 and O2. They generally produce a lot more O2 than CO2, though.

Next, once fermentation has completed (say while bulk aging) the headspace in your carboy cannot contain 100% CO2 unless you are in the habit of back-purging that space after you have installed an airlock. Although CO2 is heavier than O2, the laws of gas diffusion do still apply, and in a very short time (measurable in seconds at most) a layer of CO2 over the liquid will be substantially mixed with atmospheric gases once the stopper and lock are removed.

Finally, there can be an advantage to stirring/shaking, especially in initially high gravity musts. The yeast will eventually slow down their rate of CO2 production, as the ethanol concentration rises, and eventually most, if not all, the active cells will no longer excrete enough gas to provide them with the "lift" that they get from riding the microbubbles through the liquid column. Since they don't swim on their own, they eventually all settle out in the lees layer. Active cells at the surface of the lees do continue to metabolize sugars in the must but those below that thin surface layer of the lees are eventually starved out, and they die. If you keep the lees layer from settling for too long by stirring you keep more active cells in suspension in the liquid and your fermentation will complete more quickly, and more cleanly, than if you allow everything to be static. This usually only makes a noticeable difference in high gravity musts but believe me that difference is very noticeable (from personal experience).

 

[blackwaterbrewer]

i make blueberry mead every year. the berries will float for a while, then drop out like a krausen. just leave it.