Sulfite at bottling

[Claude Jolicoeur]

I did a few tests on my 2014 ciders, adding sulfite at different dosages at bottling time, to see if I could taste it at drinking time.
I did the test on 2 ciders. Both were bottled once stabilized at SG 1.012 and 1.013, in April and June 2015, i.e. 9 and 7 months ago respectively.
Micro dosage of DAP was added to provide a bit of in-bottle conditioning to give some carbonation, as described page 274 of The New Cider Maker's Handbook.
At the same time, sulfite was added at 2 different dosages, a lower level (30 - 40 ppm of SO2) and a higher level (70 - 80 ppm). I also kept unsulfited bottles for control.

I tasted and tested the bottles these last days, and obtained somewhat unexpected results...

1- All of the sulfite vanished! I couldn't taste the sulfite in any of the bottles. Testing for SO2 indicated there was no free SO2 left. Testing for total SO2 did indicate levels in accordance with what was added. Hence all of this sulfite has been bound with the product of the in-bottle fermentation. This was quite unexpected - I really thought that after a dosage of 75 ppm, enough sulfite would have remained free so I could have measured and percieved it.

2- Effect on acidity: sulfited bottles had higher acidity than unsulfited ones, indicating probable MLF in unsulfited bottles. The sulfite addition would then have inhibited the lactic acid bacteria, which makes sense. Actually, the TA of bottles sulfited at the higher dosage didn't change, the unsulfited ones had a reduction of 1 to 1.5 g/L malic, and the medium dosage ones were somewhat intermediate.

3- Effect on carbonation and final SG: sulfited bottles had more carbonation, and were dryer (SG 2 to 3 points lower) than unsulfited bottles. For the cider that was bottled at SG 1.013, the unsulfited bottle was at 1.010, the bottle with lower sulfite was at 1.008, and the bottle with higher sulfite dosage was at 1.007. Similar results were obtained for the other cider. This is a side effect which really surprised me. The only reasonable explanation I can think of is that, in the unsulfited bottles, part of the DAP nutrients were used by the LAB to perform MLF, and in consequence there was less nutrients available for the yeast, hence less alcoholic fermentation and less CO2 produced. Would this make sense?

All of this tells me I'll have to make other tests with my 2015 ciders... some with increased dosages of sulfite - maybe up to 150 ppm?
Also some with no nutrients and sorbate to inhibit the in-bottle refermentation.

I'll be pleased to read your comments...
Claude

[Andrew Lea]

On 16/01/2016 22:02, Claude Jolicoeur wrote:

>
> 1- All of the sulfite vanished ....This was quite unexpected - I really thought

> that after a dosage of 75 ppm, enough sulfite would have remained free
> so I could have measured and percieved it.

This is normal! It is (almost) impossible for free SO2 and an active
yeast fermentation to co-exist. The acetaldeyde produced by the yeast
binds up the SO2 and if there isn't enough acetaldehyde, then the yeast
produces more until it is all bound. It's the fermenting yeast's way of
detoxifying the SO2.

>
> 3- Effect on carbonation and final SG: sulfited bottles had more
> carbonation, and were dryer (SG 2 to 3 points lower) than unsulfited

> bottles...... This is a side effect which really
> surprised me.

Actually the stimulation of yeast growth by low level SO2 is quite well
known and referred to in the older wine literature (eg Ribereau Gayon
Traité d'Oenologie) though not so much nowadays. After the lag phase, a
sulphited fermentation will overtake a non-sulphited one in speed and
ultimate sugar utilisation. The reasons are not too clear - Ribereau
Gayon suggests it may be due to binding up of natural yeast inhibitors
by the SO2 or by preventing the loss of oxygen (oxygen being important
for strong yeast cell walls and completion of fermentation). I don't
recall seeing any academic discussions of this in recent years (but I
haven't searched too hard!). It is mostly described in the context of
wild fermentations so of course it may be due to interactions between
microorganisms. I'm not sure if it has been demonstrated with cultured
yeasts.

I would add that anecdotally I observed the same effect when bottling
keeved ciders one year with and without SO2 (the ones with added SO2
became dryer than those without). It's odd and quite counter-intuitive!

Andrew

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

[Claude Jolicoeur]

Andrew Lea a écrit :

This is normal! It is (almost) impossible for free SO2 and an active
yeast fermentation to co-exist. The acetaldeyde produced by the yeast
binds up the SO2 and if there isn't enough acetaldehyde, then the yeast
produces more until it is all bound. It's the fermenting yeast's way of
detoxifying the SO2.

Interesting... This would mean it is virtually impossible to have some free SO2 with bottle conditioning. Either the sulfite dosage would be high enough to inhibit the fermentation and in that case the free SO2 would be very high at drinking time, either all the sulfite will be bound if the yeast can survive and ferment the sugar.
The only way then to have some free sulfite would be if the cider is disgorged and the sulfite is added with the liqueur de dosage.

 

Actually the stimulation of yeast growth by low level SO2 is quite well

known and referred to in the older wine literature [...]  It is mostly described in the context of

wild fermentations so of course it may be due to interactions between
microorganisms.

Do you think the hypothesis of a share of the available nutrients between LAB and yeast makes sense?
 

I would add that anecdotally I observed the same effect when bottling
keeved ciders one year with and without SO2 (the ones with added SO2
became dryer than those without). It's odd and quite counter-intuitive!

Have you checked the TA of the sulfited cider vs the non sulfited one?

Claude

[Andrew Lea]

On 17/01/2016 15:48, Claude Jolicoeur wrote:


> Interesting... This would mean it is virtually impossible to have some
> free SO2 with bottle conditioning.

I believe that to be the case. You might also ask why you would want or
need any persistent free SO2 in that situation? The reducing environment
of the yeast itself should take care of oxidation issues. You might be
worried about lactic acid bacteria, but LAB (unlike yeasts) are
susceptible to the presence of bound SO2 (Ribereau Gayon again!).

> Actually the stimulation of yeast growth by low level SO2 is quite well
> known and referred to in the older wine literature [...] It is
> mostly described in the context of
> wild fermentations so of course it may be due to interactions between
> microorganisms.
>
>
> Do you think the hypothesis of a share of the available nutrients
> between LAB and yeast makes sense?

Probably. I'm not saying your hypothesis or mine is correct! I was just
saying that the counter-intuitive stimulatory effect of SO2 on yeast
growth has been known for a long time.

>
> I would add that anecdotally I observed the same effect when bottling
> keeved ciders one year with and without SO2 (the ones with added SO2
> became dryer than those without). It's odd and quite counter-intuitive!
>
>
> Have you checked the TA of the sulfited cider vs the non sulfited one?

No I never did. Sorry, no data. And it's too late now ;-)

[Claude Jolicoeur]

 Andrew Lea wrote:

I believe that to be the case. You might also ask why you would want or
need any persistent free SO2 in that situation?

It is mostly that I want to understand what happened to a cider when I can taste the sulfite as I drink it...
For example, I recently drank a pear cider Methode Traditionelle from Napoleone in Yarra Valley that I brought back. It had a quite perceptible sulfite taste. Upon testing, it was at a little over 30 ppm free SO2.
This is a Methode traditionnelle and this means the sulfite was added with the liqueur de dosage. If the sulfite would have been added at bottling, it wouldn't have been possible to taste it.

The other thing is that bottle-conditioned natural cider is a bit fragile, doesn't travel well - for example, in some festivals in North America, we often are offered some French natural farm ciders that are badly off. The first times, I was surprised by their taste. But now I know when they are off because I've had them at the farm and they were completely different there... I was thinking if these ciders were sulfited at bottling time, maybe they would travel better. But unfortunately this wouldn't work since all the sulfite vanishes with the bottle conditioning.

All this means that if a producer wants his cider to have some free SO2 for protection and better conservation of the bottles between the moment the cider leaves the cidery and the moment it is drank, he can't do it with a simple bottle-conditioned cider. He'll need to do a forced carbonation, or a process that permits him to add the sulfite after the prise de mousse is done, like a closed tank (Charmat) or a champenoise method.

Claude

[Dick Dunn]

On Sun, Jan 17, 2016 at 07:34:05PM -0800, Claude Jolicoeur wrote:
...snip...

> The other thing is that bottle-conditioned natural cider is a bit fragile,
> doesn't travel well - for example, in some festivals in North America, we

> often are offered some French natural farm ciders that are badly off...

Claude, I think this is due to a combination of somewhat weak attention to
the cidermaking and mishandling in distribution.

That is, first I think the cidermaker isn't really paying attention to the
fact that the cider is going to be shipped thousands of miles (or km:) and
also will be sitting around in various places--shipping container,
warehouse, store--for possibly months. It takes a different attitude to
cidermaking to produce a cider which stands up to this compared to holding
the cider in a cool, dark cellar at the cidery. If a keeve just barely
succeeded, it may be that the cider really isn't stable for the longer
term.

That said, there is also plenty of bad practice in the import/distribution
chain particularly in the US. Some are much more attentive than others.
Keeping cider in a warehouse with poor temperature control will kill it
if it hasn't been processed to survive that. Also I say "particularly in
the US" because our laws require two intermediaries between the producer
and the shop--namely the importer and a distributor. Shops certainly can't
import on their own, but in fact also they cannot buy directly from the
importer. So, too many places for things to go wrong...the importer may be
as careful and kind to the cider as you'd like, but then a distributor can
pick it up and put it in an un-refrigerated truck for a two-day trip in the
summertime.
--
Dick Dunn rc...@talisman.com Hygiene, Colorado USA

[jo...@chapeldown.com]

Interesting findings in your trial Claude, particularly with the effect on carbonation. I think its unlikely that the LAB would utilise DAP as amino acids required by LAB cannot be produced from inorganic nitrogen. It would be interesting to see glucose/fructose levels in the resulting ciders. The only theory I can think of for this (assuming you didn't introduce yeast for secondary ferment) is that the dose of SO2 pre-bottling knocked out some of the non-sacc yeasts (which could have been competitive), leaving only yeast strain/s which were more able to dominate and ferment in stressful conditions of high ABV/low O2/high pressure/high SO2. This is a long-shot theory, but it was all i could think of

[Claude Jolicoeur]

Le lundi 18 janvier 2016 15:31:02 UTC-5, jo...@chapeldown.com a écrit :

Interesting findings in your trial Claude, particularly with the effect on carbonation. I think its unlikely that the LAB would utilise DAP as amino acids required by LAB cannot be produced from inorganic nitrogen.

Thanks for this information, I wasn't aware of that.
Do you have an idea of the quantity of nutrients that LAB require to do its work, compared to what yeast needs.
For yeast, we have a pretty good idea, and the maths is simple: yeast biomass contains 9 to 10% N, and DAP contains 21% N. One gram of DAP will permit building a bit over 2 grams of yeast biomass. And one gram of yeast biomass is about 15 to 20 billion cells. And we know we need between a quarter and half a million yeast cells per mL to make a good bottle-conditioning. So, from 10 ppm DAP, we have 2 ppm N, which can permit building a population of about 20 ppm of yeast biomass, or 350000 cells per mL, which is a good number for a bottle conditioning.

 

It would be interesting to see glucose/fructose levels in the resulting ciders.

What would this tell you? Can the ratio of glucose on fructose give indication on what is happening?

 

The only theory I can think of for this (assuming you didn't introduce yeast for secondary ferment) is that the dose of SO2 pre-bottling knocked out some of the non-sacc yeasts (which could have been competitive), leaving only yeast strain/s which were more able to dominate and ferment in stressful conditions of high ABV/low O2/high pressure/high SO2. This is a long-shot theory, but it was all i could think of

No I didn't introduce yeast. But the non-sacc yeasts, if not knocked in the unsulfited cider, would also consume sugar and produce CO2... Only maybe slightly less efficiently. Could this account for the quite large difference observed?

Claude

P.S., to Dick, thanks for the clarifications on US distribution...

[Miguel Pereda]

 Claude. Do your calculations are valid for an environment of sulfites and SG 1013?

[Claude Jolicoeur]

Hola Miguel,
I don't see how the SG or the sulfite would change the calculation.
It is just a question of how much N is required to build a population of yeast, and to evaluate the amount of N that may be available and used for this.
As of the number of yeast cells required for bottle conditioning, this comes from French cider makers, who count the yeast cells with a microscope prior to bottling. This is the number they look for for insuring a proper bottle conditioning. When there is too much, they would filter to reduce the number, and when there isn't enough, they would add some yeast.
For my part, instead of adding yeast, I add a controlled amount of DAP that will just permit the yeast to build the population wanted, and no more.
Equivalent result could be achieved by adding yeast. Assuming a perfectly stable cider at SG 1.013. If it is stable, we may assume there is no more nutrients, and that the yeast population is very small. Adding then about 350000 cells per mL would just insure the proper bottle conditioning. This is about 20 ppm of yeast biomass, or 2 grams of dry yeast per hL. (compare this to standard yeast inoculation rate which is 25 grams per hL)
Claude

[Miguel Pereda]

Claude.
My focus, is another.
I think that the simple calculation you do would be closer to reality in the exponential growth phase of the yeast which is when the number of them, if nutritientes are adequate, increase.
In other phases of fermentation perhaps DAP's contribution is not as effective in generating growth in the number of yeasts. In these other phases, perhaps nitrogen is used only to generate or regener transport proteins that act facilitating the exchange of products through the celular wall,  increasing the speed of existing fermentation yeasts, without increasing their number significantly. It is my opinion.

[Claude Jolicoeur]

Le mardi 19 janvier 2016 12:08:12 UTC-5, Miguel Pereda a écrit :

Claude.
My focus, is another.
I think that the simple calculation you do would be closer to reality in the exponential growth phase of the yeast which is when the number of them, if nutritientes are adequate, increase.

Yes, I agree.
 

In other phases of fermentation perhaps DAP's contribution is not as effective in generating growth in the number of yeasts. In these other phases, perhaps nitrogen is used only to generate or regener transport proteins that act facilitating the exchange of products through the celular wall,  increasing the speed of existing fermentation yeasts, without increasing their number significantly. It is my opinion.

Well this is really very empirical. It comes from observations of how much fermentation and carbonation we get when there is a certain yeast population present at bottling time, or potentially present from the amount of N.
There is no tentative to model what happens in reality as exchanges or biochemical transformations.
All I can tell you is that it works! I can predict quite accurately how much carbonation I will get with this approach.
And even ciders that have been bottled for 2 years or more don't show overcarbonation.
However I do keep my bottled cider in optimal conditions - what would happen if it had to travel and stay in overheated storage, I don't know...
This is one of the reasons I wanted to make tests with sulfite at bottling time...
Claude

[jo...@chapeldown.com]

On Monday, January 18, 2016 at 11:30:46 PM UTC, Claude Jolicoeur wrote:

Le lundi 18 janvier 2016 15:31:02 UTC-5, jo...@chapeldown.com a écrit :

Interesting findings in your trial Claude, particularly with the effect on carbonation. I think its unlikely that the LAB would utilise DAP as amino acids required by LAB cannot be produced from inorganic nitrogen.

Thanks for this information, I wasn't aware of that.
Do you have an idea of the quantity of nutrients that LAB require to do its work, compared to what yeast needs.
For yeast, we have a pretty good idea, and the maths is simple: yeast biomass contains 9 to 10% N, and DAP contains 21% N. One gram of DAP will permit building a bit over 2 grams of yeast biomass. And one gram of yeast biomass is about 15 to 20 billion cells. And we know we need between a quarter and half a million yeast cells per mL to make a good bottle-conditioning. So, from 10 ppm DAP, we have 2 ppm N, which can permit building a population of about 20 ppm of yeast biomass, or 350000 cells per mL, which is a good number for a bottle conditioning.

Nutrition for LAB is quite complex, their main energy source is from hexoses, but can utilise other sugars. The decarboxylation of L-malic to L-lactic will also yield some ATP as a byproduct really of the main goal of pH adjusting the medium, after they've finished malic they usually move on to citric which would also yield some energy. Regarding a nitrogen source, the specific amino acid requirement is strain dependent and although quite a lot of work has been done on this there are conflicting results, a broad spread of amino acids would be the best answer i'd guess, but even if they're not present or all used, LAB can break down peptides and proteins as well, so they're really not that fussy!!

 

It would be interesting to see glucose/fructose levels in the resulting ciders.

What would this tell you? Can the ratio of glucose on fructose give indication on what is happening?

This would just confirm the amount of unfermented sugar remaining which would be more precise than making an assumption from the SG.

 

The only theory I can think of for this (assuming you didn't introduce yeast for secondary ferment) is that the dose of SO2 pre-bottling knocked out some of the non-sacc yeasts (which could have been competitive), leaving only yeast strain/s which were more able to dominate and ferment in stressful conditions of high ABV/low O2/high pressure/high SO2. This is a long-shot theory, but it was all i could think of

No I didn't introduce yeast. But the non-sacc yeasts, if not knocked in the unsulfited cider, would also consume sugar and produce CO2... Only maybe slightly less efficiently. Could this account for the quite large difference observed?

 

Possibly/probably not, but it was the only thing I could think of that may have had some effect, as you've said, the results are counter-intuitive which is what piqued my interest in the first place. 

[Nathan Shackelford]

If previous applications of S02 have cleared up all the spoilage bacteria, what will cause the cider to degrade if the S02 is gone after bottle conditioning? I know temperature and remaining yeast may make some changes, but it seems like it should be pretty stable. I guess if that were true the cider being imported would always taste as good as when it left the cidery?

If you force carbonate and add S02, wouldn't the threshhold for tasting it be met?

[Claude Jolicoeur]

Le lundi 25 janvier 2016 22:29:40 UTC-5, Nathan Shackelford a écrit :

If previous applications of S02 have cleared up all the spoilage bacteria, what will cause the cider to degrade if the S02 is gone after bottle conditioning? I know temperature and remaining yeast may make some changes, but it seems like it should be pretty stable. I guess if that were true the cider being imported would always taste as good as when it left the cidery?

Well, I don't think the previous applications of SO2 would have cleared all bacteria - sulfite will I think keep these bacteria under control and prevent them from growing a population while there is some free or molecular SO2 present. And once all the SO2 is bound, the protection effect is lost. This is my understanding anyway. There is also the question of oxydation which is another story...

If you force carbonate and add S02, wouldn't the threshhold for tasting it be met?

I think so. Probably that most of the ciders where the sulfite may be tasted at drinking would have been treated by sterile filtration and sulfite+sorbate addition, and carbonated.
But as I said in a previous post, I have also tasted some that were from a traditional method, and in that case, the sulfite would have been added at disgorging time.
Claude