Perfect temperature profile for fermentation

[Fergal Connon]

Hi all, I've been thinking of posting this topic for a while but I figure now is a good time with recent topics involving multiple racking and arduino boards.

I have built myself a pretty neat setup (if I do say so myself) of a fermentation chamber consisting of a commercial sized fridge and a 100l conical tank. The fridge has been modified to be run by a brewpi ( http://www.brewpi.com/ ) complete with heater inside. I have built this specifically with cider in mind. For those who do not follow the link, basically the brewpi will take control of the fridges compressor and heater and switch on whichever is required for the temperature the end user dictates. The temperature is logged and the exact same temperature profile can be ran again. On a side note it could potentially remove one of the variables when doing yeast trials but that was a heated debate!

My aim in putting together this equipment is to produce an off dry to medium (sg 1004 - 1012) cider naturally using the technique of multiple rackings. In theory I will be able to open the valve on the bottom of my tank to discard the yeast lees with the added bonus of being able to do it on a really cold day (cold crashing the tank to 2 degrees for example) and at a time that suits me.

Now to my questions:
If you were to define the optimum temperature profile for a wild yeast fermentation what would it look like?
Will I get any benefit from running cultured yeasts at temperatures other than what is specified on the pack?
Have I wasted my time?

Thanks to all who contribute to this gem of a forum, where would we all be without it!

Fergal.

[Fergal Connon]

I should add, I have two very different sources of fruit / juice. One is from my orchard and nearby orchards that contain very old unfertilized trees. It is suspected that the pear trees are at least 60 years old given my inlaws grandparents remember the trees as children, they are also massive and unidentified. I might post a picture of the pear when the time comes to see if anyone recognises it.
My other source is from a huge company that produces apple juice year round. They also supply juice by the tanker full to local cideries in it for the quick buck.

I suspect I will have very different results with both juices!

[Fergal Connon]

Anyone?

Apologies for pushing my own topic.

[Andrew Lea]

On 21/01/2015 09:02, Fergal Connon wrote:
> Anyone?
>
> Apologies for pushing my own topic.
>

I don't think you'll get much response because most people here just
have to make do with whatever nature provides. Very large cidermakers do
run thermostatted fermentations at 20+C but mostly so they can get the
quickest throughput without the danger of overheating. Time is money for
them.

> If you were to define the optimum temperature profile for a wild yeast fermentation what would it look like?

I would suggest as low a temp as possible, maybe around 8 - 10C? That
mimics UK winter conditions and will probably give you a 3 - 4 month
fermentation. Temperature will probably have a large influence on a wild
fermentation because it is a mixture of different organisms and so there
will likely be a lot of 'natural selection' at different temperatures.

> Will I get any benefit from running cultured yeasts at temperatures other than what is specified on the pack?

Probably not. I would go for the lowest temp in the specified range just
to conserve as many fermentation esters as possible. The volatile
profile may vary with temperature in any case - AFAIR with most wine
yeasts higher temperatures tend to generate more fusel alcohols.

I think you are also right to suggest that the nature of the original
juice and especially its inherent nutrient level will have a very marked
effect on fermentation behaviour.

Andrew

--
near Oxford, UK
Wittenham Hill Cider Portal
www.cider.org.uk

[Fergal Connon]

Thanks for your response Andrew, much appreciated.

I suppose some background would have helped. I live in Melbourne (originally from Northern Ireland) and generally the temperatures when I am ready to start fermenting can still be quite high, on average about 20 degrees. When I have a lot of early varieties it can be 30 degrees. I often have fermentations completing in a week at these temperatures which is not ideal for me - I often get the sulphur notes which can be difficult to shake. Last year I took the route of freezing about 80 litres worth of apples just so I could let them ferment in the middle of winter. It made a huge difference to the nose of the cider which smells delicious but from advice I got on here I was told that wild yeasts and frozen apples probably wouldn't work out too well. So here I am!

I was hoping this post might encourage some anecdotal conversation about the effects of temperature on the end product - i.e. I remember the winter of 98 was really cold and I had a great cider etc etc!

Andrew picking up on your reply about the 'natural selection' at different temperatures and trying in vain to recall the specifics of wild fermentation I have often read you describing how it is a succession of yeasts that provide an ideal wild fermentation. Do you have any thoughts on how these may be effected by temperature and what I might be able to do to swing the balance in my favour? Or am I thinking too much?

On another note, assuming I have successfully arrived at a stable cider with s.g 1010 do you foresee me having any difficulties in raising the temperature to promote some mlf? If not, what would be the ideal temperature for this to take place?

Cheers,

Fergal.

[Andrew Lea]

On 21/01/2015 22:27, Fergal Connon wrote:

> I have often read you describing how it is a
> succession of yeasts that provide an ideal wild fermentation. Do you
> have any thoughts on how these may be effected by temperature and what I
> might be able to do to swing the balance in my favour?

This paper which you can download for free may be of interest
http://onlinelibrary.wiley.com/doi/10.1046/j.1472-765X.1997.00340.x/pdf

>
> On another note, assuming I have successfully arrived at a stable cider
> with s.g 1010 do you foresee me having any difficulties in raising the
> temperature to promote some mlf? If not, what would be the ideal
> temperature for this to take place?

I am concerned that you are placing a lot of reliance on 'cold crashing'
to stabilise a fermentation with residual sugar. As has often been
discussed here, that is only likely to be successful in amateur hands if
you start with low nutrient and / or keeved juice where the yeasts are
already struggling.

It is true that the technique is used commercially in Australia on
regular apples but 'cold crashing' is only a part of what needs to be
done to ensure stability. After the cider has been chilled to inhibit
fermentation and to part flocculate the yeast, it is then cross-flow
ultrafiltered to remove virtually all yeast cells. The metastable sweet
cider is then bottled and pasteurised, or is sterile filtered and
bottled using DMDC (Velcorin) as a back-up to kill any stray yeasts.
This is done using a pressure tank (the Moscato process) if a naturally
carbonated cider is required. This kind of technology is not available
to the amateur.

The sort of thing you are talking about does take place in low nutrient
keeved ciders which are bottled sweet and which undergo a slight
continued yeast fermentation in bottle. Often a wild MLF will also take
place in these ciders during the summer after bottling. But if your
cider is not stable with respect to further yeast fermentation because
the nutrients are too high, then you have far more to worry about than
MLF or not!

[Fergal Connon]

Thanks for your response Andrew and for the link provided. That's an interesting read for me and what I have taken from it is that the Kloeckera apiculata is more likely to thrive at lower temperatures. From reading your website you have said that this is the yeast strain that produces the more interesting flavours but is much less tolerant to S02. I'll give it a go and see what happens. One benefit I will have from my system is I will be able to keep the temperatures a bit higher to get the fermentation going and then drop it down to the 8-10 degree range. Perhaps then I wont run into as many problems with mould as it gets going?

I am concerned that you are placing a lot of reliance on 'cold crashing'
to stabilise a fermentation with residual sugar. As has often been
discussed here, that is only likely to be successful in amateur hands if
you start with low nutrient and / or keeved juice where the yeasts are
already struggling.

I remember the discussion well, I think I may have been one of the chief protagonists, although in my defence I have always been dubious of the 'cold crashing is the answer to all my problems' philosophy! My aim with the technique I am suggesting is more to do with multiple rackings of the cider. The benefit of my temperature control being that I can 'cold crash' the cider every time I rack it. I should say though I am quite relaxed about the outcome. If I cannot achieve a natural cider with some residual sugar then so be it, it is certainly not the end of the world for me. To be honest I am just excited to be in a position to try out these techniques.
I have always wanted to give keeving a go but never believed my current apples to be suitable as they are mostly dessert / cooking apples (I have planted 10 or so different true cider apples and am waiting patiently for them to start bearing some fruit). As mentioned though I do have a good supply of pears which will bring the PH up into a better range. I'll certainly be giving it a go although it may be on a 50/50 apple / pear split!

Thanks again for taking the time to give me some thoughtful and measured responses. You must have the patience of a Saint!

[William Grote]

Could you post a link with pictures of the Fridge and conical, I want to make a similar set up this summer using the BrewPi-Spark

[Fergal Connon]

https://onedrive.live.com/redir?resid=22498B648CDE0147!10640&authkey=!AKDvWNCPQfMyaWw&ithint=folder%2cPDF

I'll add a few more in there soon. The fridge is now complete and working, unfortunately the tank isnt quite there yet but one good saturday morning and it should be finished. There is a pdf in there of what it will look like finished. The brewpi works really well - the spark should be even better.