BOTTLE CONDITIONING WITH FRUCTOSE AS A PRIMER AND 71B AS THE YEAST

[Tom Bell]

After 120 days, some of my batches are flat-lining at 1.008-1.009.  All have undergone spontaneous (wild) fermentation.  All had between two and four stabilization rackings to remove as much nitrogen as possible. I'm pleased with the results and the final SG.  This is exactly what I wanted to achieve. My end game is to bottle condition for 60 days, disgorge, and age for another 60-90 days before drinking.  I am assuming that the bulk of the residual sugar is fructose.

In the past, I have primed my finished cider with sufficient dextrose to bring the SG back up to 1.011 and added EC-1118 at bottling.  I disgorged when the internal pressure hit 4 atmospheres.  This year, I am considering the use of fructose instead of dextrose for bottle conditioning.  My goal is to produce a slightly sweeter cider and given that the perception of sweetness is 1.2-1.7 times higher than sucrose, and nearly twice as sweet as dextrose, it seemed reasonable to substitute fructose for dextrose as a priming sugar to bump the final sweetness up.  According to Scott Labs, Lalvin 71B is at the bottom of the range of 20 commercial yeasts in Its ability to metabolize fructose.  This characteristic is independent of YAN concentration and fermentation temperature.  I expect the combination of fructose and 71B to preserve more residual sugar after bottle conditioning and shave off some acidity.

So, what could go wrong?  My greatest worry is that this secondary fermentation will stall before dropping the SG back down to 1.004-5.

Before committing to this, I would appreciate any comments based on your collective experiences and suggestions for modifying my approach. 

Cheers

Tom Bell

[Claude Jolicoeur]

Tom,
Yes, you seem to have your cider well stabilised at 1.008. From this you can estimate there is currently 16.5 g/L of residual sugar.
From there on, you have a couple of options.
If you aim for 4 Atm of internal pressure at 20C, you need for that a drop of SG of about 6.5 points in the bottle, or ferment about 14 g/L of sugar.

Option 1, if you don't add any sugar, you'd end up at a SG of 1.002 - probably a bit too low for what you want to do.

Option 2 would be to add some sugar, no yeast, and just the amount of DAP to ferment those 14 g/L of sugar - that would be about 15 ppm of DAP. For example, you could add 12 g/L of sugar, the 15 ppm of DAP, and would obtain a finished sparkling cider at SG 1.007.

Option 3, if you add some yeast, you need to add only minute amount - any normal dosage of yeast will ferment all the sugar there is. I would not count on 71B and fructose to insure you will keep this under control.
For example, you could add 25 ppm of dry yeast cells (i.e. 2.5 grams in 100 L), this would make a yeast population of approximately half a million cells per mL. In the absence of nutrients such a small population will not increase in number and will die after fermenting what you need for producing a good sparkle.

Claude

Le vendredi 16 mars 2018 13:32:44 UTC-4, Tom Bell a écrit :

After 120 days, some of my batches are flat-lining at 1.008-1.009.  All have undergone spontaneous (wild) fermentation.  All had between two and four stabilization rackings to remove as much nitrogen as possible. I'm pleased with the results and the final SG.  This is exactly what I wanted to achieve. My end game is to bottle condition for 60 days, disgorge, and age for another 60-90 days before drinking.  I am assuming that the bulk of the residual sugar is fructose.

[Wayne Bush]

Tom, I won't presume to offer advice but would put my money on Claude's option 2.  Even with racking, there's surely yeast in the cider that will reactivate and carbonate the cider with the right amount of added nutrient so seems unlikely the bottle fermentation would stall.  But curious what the temperature of the cider has been where you are since the cider reached 1.008 as I don't see a temperature line on your chart.  Are you planning to filter the cider before you bottle it?  Also, after you disgorge will you do anything else to stabilize the cider (i.e., pasteurize), or in your experience is the riddling/disgorging sufficient to ensure the cider remains stable in the bottle?  Wayne

[Tom Bell]

Hi Claude,

Thanks for laying out some options.  

Last year, I used option 2 on one of my wild ferments and added 10 ppm DAP and enough dextrose to bring the SG up to 1.011.  As expected, the wild yeast woke up and fermented some but not all of the residual sugar.  However, it only got to 38 psi, on the low side to disgorge and still retain sufficient carbonation for a good sparkling cider so I didn't risk disgorging  The flocculation of the wild yeast did not produce a compacted sediment.  Ninety days after bottling, a very gentle twist of the bottle puts a cloud of lees halfway to the top of the bottle.  It tastes fine but is less aesthetically pleasing to my eye.  I guess I should have bumped the DAP up to 15 ppm to get enough pop to disgorge these bottles.  I will probably try this again this year.

With respect to option 3, I wondered how or even if the initial pitch rate has an impact on the final SG. Two papers seemed to suggest an answer but the experimental procedures optimize everything except the pitch rate. Based on a paper that measures biomass rather than final SG, the initial pitch rate retards the rate of growth if it is low enough.  However, the ultimate yeast concentration reaches the same level as higher pitch rates.  Low initial cell counts have a growth curve with longer lag and log phases but the yeast cell concentration is nearly identical at the end of 27 hrs.  The four fermentation curves below represent pitch rates of 5, 10, 15, and 20 ml of a standard 100 ml yeast concentrate. The yeast is Kluyveromyces fragilis not S. cerevisiae.

This paper gives a clearer picture of the impact of pitch rate on residual sugar and they used S. cerevisiae.  Like the graph above, fermentation at the lowest pitch rate is slower but reaches the same residual sugar concentration as all the other pitch rates.

Based on these two papers, the pitch rate does have an impact on fermentation, most notably the rate of yeast growth and in the last case, the taste of the final product.  It does not seem to have any impact on the residual sugar, at least under ideal nutrient conditions. I guess we should not be too surprised by this since there are so many of us that don't pitch any yeast at all after pressing and we do it because we think the flavor of spontaneously fermented cider is superior to cider fermented with commercial yeast.  Even if you disagree about which is better they taste different.

In conclusion, this still does not address how different pitch rates work in a nitrogen depleted cider.  I suppose it is possible that controlling the pitch rate in a nutrient deprived environment could preserve more residual sugar but finding evidence for or against that in the literature might be more work than just trying it.

[Tom Bell]

Hi Wayne,

Here is the temperature history for this cider.  I am a garage fermenter and have limited control over the temperature.  Between day 30 and day 68, the fermentation got down into the high 30s for at least a week but I was doing other things and didn't record it.

This cider is clear enough to read the headlines on the newspaper through a five gallon carboy and make out the lines in the articles so there is no need to filter it.  There are still scattered bubbles and a quarter inch of lees so I know I can rev up the yeast with some DAP and agitation.  Or, I can start a secondary fermentation at bottling time with a commercial yeast.  I'm still interested in the composition of the residual sugar.  My son could run this through HPLC where he works and I could get a quantitative measurement of any or all of the compounds in solution or in the lees if I wanted.  I may do that or leave it a mystery and wing it with either my original plan, jump on Claude's option 2, or do half one way and half the other way.  I kind of like the ambiguity at the boundary between art and science.

Upon disgorging, I will add about 50 ppm sulfite to make sure it does not go through MLF in the bottle.  In the past, disgorging and the depleted nitrogen content has prevented a re-start of fermentation.  Could be luck but so far no problems of that sort.  My oldest disgorged bottles are three years old.  The older they get the better they taste.  I have a problem with demand so it is hard to squirrel away very many bottles year to year even though I bottle 20-30 cases a year.

My real problem is consistently balancing acid and sweetness.  Every year I try something new and the results have generally been good but it is an itch I can't stop scratching.  When I have it wired, I will probably get bored and move on to something else.  I have been looking into fermenting sake.  Now that looks like a real challenge.

[Claude Jolicoeur]

Le samedi 17 mars 2018 18:40:39 UTC-4, Tom Bell a écrit :

With respect to option 3, I wondered how or even if the initial pitch rate has an impact on the final SG. Two papers seemed to suggest an answer but the experimental procedures optimize everything except the pitch rate. Based on a paper that measures biomass rather than final SG, the initial pitch rate retards the rate of growth if it is low enough.  However, the ultimate yeast concentration reaches the same level as higher pitch rates.  Low initial cell counts have a growth curve with longer lag and log phases but the yeast cell concentration is nearly identical at the end of 27 hrs.

Tom, these studies assume there is yeast population growth - and for this there has to be some nutrients in the must. In your case, there is no more nutrients left, hence the yeast population will not increase after inoculation. All you will have is the number of cells you put in there and these have a finite lifespan. Hence they will ferment only part of the sugar.
I am not aware of scientific studies on this, but I know many cider makers in France work successfully this way. The rule of thumb is that when the nutrients are exhausted, a population of about half a million cells per mL is what you need for a good prise de mousse. I have also tested it and it worked for me.
Claude

[Tom Bell]

Thanks again Claude,

I'll have a shot at this with half of this batch.  I will also see how my fructose and 71B idea works with the other half.

Does the pitch rate you recommended hold true for all yeast varieties?  Can you recommend a specific yeast that will be most likely to succeed?

Tom

[Claude Jolicoeur]

Le dimanche 18 mars 2018 10:50:37 UTC-4, Tom Bell a écrit :

Can you recommend a specific yeast that will be most likely to succeed?

No, unfortunately. You'll have to make some tests... I would think it should work fine with the 71B.
Ideally, you should have a microscope and count the existing population, and add only if the population is too low...
However, as yous cider is perfectly clarified and stable, you can probably safely assume this existing population is very low.

If you like numbers, note also the equivalence in the weight of N: DAP contains 20% N while yeast biomass contains roughly 10% N. Hence 10 ppm DAP permits to grow a maximum of 20 ppm of yeast biomass... So, theoretically, it would be equivalent to add 10 ppm DAP or 20 ppm dry yeast.
Claude

[Tom Bell]

I've been thinking about a microscope.  I had one but donated it to a school in Niger when I stopped working there.  Is 41b a killer strain like EC 1118?  If so, I probably don't need to worry about my wild yeast making a comeback if I pitch a limited dose of 41b.  I wouldn't think it would be a good idea to use EC-1118 since it is so robust.

All scientists like numbers.  Engineers too!  Nice to see a quantitative approach to fine tuning my end game.

[Claude Jolicoeur]

Le dimanche 18 mars 2018 12:03:35 UTC-4, Tom Bell a écrit :

I've been thinking about a microscope.  I had one but donated it to a school in Niger when I stopped working there.  Is 41b a killer strain like EC 1118?  If so, I probably don't need to worry about my wild yeast making a comeback if I pitch a limited dose of 41b.  I wouldn't think it would be a good idea to use EC-1118 since it is so robust.

You mean 71B? (never heard of 41b) - if 71B, it is killer sensitive. But anyway there will be no comeback as there is no nutrients in the cider - yeast cannot multiply. They can only survive for some time and die...

All scientists like numbers.  Engineers too!  Nice to see a quantitative approach to fine tuning my end game.

But numbers are only one side of it. Let's not forget these are living organisms, and with life, there can always be some unpredictable side effects.
Working with inert material (which is what engineers do) is much easier!

Claude

[Wayne Bush]

Thanks for the temperature data Tom.  FYI, I followed a similar approach to yours this year taking my cues from Claude's book and with some helpful advice from the author along the way, and just managed to stabilize my fermentation at 1.004.  But I used 71B for the primary fermentation rather than wild yeast in order to take advantage of 71B's reported ability to reduce acid from my dessert apples, and thereby increase the perception of sweetness.  I was lucky, but the result taste-wise is pretty much what I was looking for.  TA did reduce from 7.2 in the must to 6.8 in the final product.  I'll also do an in-bottle carbonation and disgorging--I've been wondering whether it would be possible at a future very small commercial level of production to achieve a product that was stable after the disgorging.  From your experience it sounds like it might be.  Only problem is that the cider, which is usually crystal clear, is slightly cloudy, which I think I'll live with rather than try to insert filtration before the bottling.  I'm going for Claude's option 2.  Good luck with yours!  Best, Wayne

[Tom Bell]

Thanks Wayne and best of luck with yours as well. 

[Tom Bell]

Wayne

I was thinking of your cloudy cider.  Have you tried any riddling aids?  They are commonly used in secondary fermentation of champagne.  Their purpose is to form more compact lees and some aids are also helpful in removing protein hazes.  This might help with your cloudy cider.  I have a particularly difficult batch which wants to rain pectin so I will probably use Ca Bentonite at 0.75 g/5 gal when I bottle it.  Last year this variety dropped a mix of dead yeast and flocculated pectin gel that reached up to 3 inches into the neck.  Disgorging got most but not all of it.  My losses during disgorging were really annoying.  There are more sophisticated formulations of bentonite and other compounds that are used in sparkling wine production.

Here are a few links:

Look at page 15 and ignore the dosage in imperial units.  The metric dosage is correct.

Scott Labs

Enartis USA

[Wayne Bush]

Tom, thanks for the suggestion and the links.  I haven't tried riddling aids before--I guess I've been lucky never to need them.  But this is probably a good year to try them out.  Given the small metric dosage found on page 15 (6 grams per hectalitre), I imagine this is something I mix into the entire batch to be bottled as I would the yeast or yeast nutrient, and not directly in the bottle with the sugar dose--correct?  Regards, Wayne

[Tom Bell]

Right.