Commercial yeast (71B) temperature resistance and pitching rates

[Francis Bonenfant]

Hello,

I've been making cider and mead for a few years now on an homebrewing scale, using mostly unfiltered juice bought at farmer's markets. I have experimented with many of the most well known yeasts before settling on Lalvin 71B for most of my batches. The malic acid metabolism is nice, I find that it simply produces better tasting brews than champagne yeast, and it stops at 14% alcohol even in a nutrient-rich must, which is nice for sweet dessert ciders and meads.

Before reading Claude's excellent book and finding this group, I was mostly on the nutrient addition, fast fermentation bandwagon. Sadly, most online homebrewing ressources and forums are centered around beer and wine, and some are chock full of dubious hearsay instead of science. Unfortunately, the few sources with serious information are often the additive manufacturers themselves. They understandably want to sell their products, so it's hard to get a truly unbiased opinion from them. Hence, there are a few questions I'd like to ask you guys. 

My first question is about the low temperature behavior of 71B (and other commercial yeasts)

According to the product specifications:
''The 71B strain is a rapid starter with a constant and complete fermentation between 15° and 30°C (59° and 86°F)''

I assume this means that 71B will ferment must to dryness in a ''commercially normal'' amount of time at 15°C, while 14°C or lower would produce a very long or incomplete fermentation (that is, probably according to fast, nutrient rich, industrial standards.)


Basically, this is my current understanding of the temperature-dependent behavior of this yeast:
Near 0°C-4°C: Will slow down to negligible fermentation rate and settle out of solution. (Cold crash)
4°C-14°C: No information
15C-20°C: Complete fermentation.
21°C+: Fast complete fermentation, possible off-tastes, stripping of flavors by vigorous CO2 bubbling and other mechanisms.

According to Claude's, it's possible to let the secondary fermentation happen slowly at 10°C or so, so it shouldn't completely stop its activities outside of the quoted temperature range.. but what would happen exactly if you started a fermentation at such temperatures? 
Has any of you ever tried a cold ferment at 5, 10, or 15°C with 71B or a similar yeast? If so, how slow was it, and did it end up with any taste differences compared to a 15-20°C ferment?
Currently, I don't have the temperature control capability to go under 18°C for my fermentations so testing it myself is unfortunately impossible.

My second question is about pitching rate.

Lallemand suggest the following for 71B:
''Pitching rate: 25 to 40 g/hl''
25g/100L seems to be in line with the 5 g packet / 5-6 gallon batch standard for homebrewing.

Now, has any of you experimented with lower pitching rates? Say, 5g/100L, or even lower.
The reason I'm asking this is that adding this rehydrated yeast biomass to the must fundamentally adds nutrients and nitrogenous substances, so in theory lowering the pitching rate in a low nutrient must should cap the yeast population at a lower number and slow down the initial vigorous fermentation phase.

My understanding is that freshly pressed apple juice will undergo natural fermentation anyways, without adding any yeasts or nutrients, so what's the lowest pitching rate that will out-compete the natural yeasts and produce a viable population of the pitched yeast?

As an extreme example, could you chuck a rehydrated 5g packet in a 10 hL tank of must and end up with a viable, but slow, 71B fermentation anyways?

Thanks,

Francis B.

[Mike Rose]

I don't have much to add on the temperature — I'm curious too actually.

As far as pitching rate, I always go with 1/2 of the recommended dose (usually ~1g per gallon). I did a 16 gallons batch just recently of 71b and I only pitched 8g. The primary fermentation temp was around 65F. It went from 1.060 -> 1.029 in two weeks (~250 FSU). Signs of fermentation started within 24 hours.

My thinking with pitching 1/2 is to force the yeast to use more nutrients to get the population built up (and add less like you mentioned). I'm not sure how accurate that is as I'm still testing.

With that said though, I always had my fermentations stick close to where I wanted them (sometimes above). However that was using Cote des Blancs. This is my first year using 71b and it seems to be a little more aggressive (Cote des Blancs primary is <150 FSU).

My apples are from wild trees — very low nutrients. 

— Mike  

[Mike Rose]

I might add that you probably want to start in the 50–60F range to get the fermentation started — even just for a few days — before placing it somewhere very cold. I would have placed my initial fermentation ideally in the 55F range, instead of 65F, to keep my FSU below 200. However, this year I had huge 16 gallon buckets I couldn't move alone after pitching the yeast.

Personally I like to get the cider to 4% ABV (1.060 > 1.030) then do my first racking and bring it somewhere much colder to ferment slowly after that. This allows the pitched yeast to dominate the fermentation and produce enough alcohol to start protecting the cider. After that I'm trying to slow things down as much as I can. 6 gallon carboys are much easier to carry out to the garage where it's well below 50F on average this time of year.

[Andrew Lea]

I'll just pitch in on the specifics of pitching rate. The key thing is to think in terms of cells per ml. 

Most commercial cider makers use a yeast pitching rate for cider which gives around 10^6 cells per ml in the juice, maybe a little more. 

Consider that an unsulphited juice off the press may easily contain 10^5  cells per ml of wild non-Saccharomyces yeast and 10^2 cells per ml of wild Saccharomyces. (Obviously these figures are very very approximate. YMMV). 

If you sulphite at the correct level, you will effectively knock out the non Saccharomyces so you only have 10^2 of Saccharomyces to worry about. You are adding a ten thousand fold excess of cultured yeast so the native Saccharomyces won't get a look in. 

If, however, you don't sulphite, you may be pitting 10^5 cells of wild non Saccharomyces  (apiculate) yeasts against only 10^6 cells of your desired culture. That's an excess of only 10 fold and since the wild non Saccharomyces are pretty vigorous in the oxidative phase, you run the risk of your added yeast being swamped in the early stages and more so if you underpitch. 

If you drop the temperature, this also favours wild yeasts over cultured yeasts, because wild yeasts (especially apiculates) may go on working down to 4C where cultured strains shut up shop. 

Neither of you guys mentioned if you add the correct levels of sulphite for pH or not. If you do, all well and good. If you don't, you run a serious risk of wild yeasts dominating your fermentation in the early stages if you underpitch, as the figures demonstrate. Later on, of course the apiculates die out as the alcohol level rises, but they may still have left their mark. 

Hope this all provides some context. As I said the figures can only be approximate but I trust they make the point. 

Andrew 

Wittenham Hill Cider Portal
www.cider.org.uk

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[Mike Rose]

Good point. For my 71b batch I added 50ppm (~6 grams) of potassium metabisulfite.  pH was 3.45 pH. Closer to a half dose.

[Francis Bonenfant]

I think temperatures starting temperatures above 15°C are simply necessary for most wine cerevisiae yeast to bud and reproduce at a reasonable rate.

A year ago I had an introduction to brewing engineering class, which while centered on beer, had a component where we modeled yeast reproduction kinetics. Unfortunately, the specifics are a bit fuzzy and I don't believe it can be directly applicable to a specific commercial strain without a ton of parameters derived from curve-fitting, so doing the experiment is necessary anyways...
Nevertheless I remember that actual cerevisiae yeast reproduction is optimal at what would be for us very high temperatures (30-35 degrees C). This temperature is way too high if we want to produce delicious alcoholic beverages and not cell biomass, but the takeaway is that while fermentation (as in the actual conversion of sugars into alcohol) can happen at sub 15C temperatures, significant growth of yeast is extremely slow under 15C.  This article from 1984 seems to point to exactly that: http://onlinelibrary.wiley.com/doi/10.1002/cyto.990050515/pdf
Between 20C and 15C, reproduction time is raised by a factor of almost four and the trend seems exponential, so under 15C you'd get very little reproduction going on. Hence why we pitch and let the reproduction phase happen at higher temperatures until the population is established.

[Mike Rose]

Thank you for that information.

Another question for you since you have used 71b a few times before...

At what point does it start to metabolize the malic acid? I ask because when I racked yesterday the acidity only dropped 0.1 g/l (8.5 > 8.4) and that could have just been user/machine error. I didn't expect for it to drop much this year, but it made me think...

I plan on trying to make this cider stick around 1.015 by racking to remove the nutrients. But does the yeast start to metabolize the malic acid as nutrients run low, or is it in parallel? I ask because I'm not sure 1) if I'm able to get this to stick if the yeast can continue to live off the acid after I remove most of the nutrients and 2) will making it stick by removing the nutrients significantly lower the amount of malic acid that metabolized?

I've also found that with Cote des Blancs and stuck fermentations that I get no MLF. I read this is because Cote des Blancs is a very "hungry" yeast and doesn't leave much for the bacteria to do their work — this makes sense as it's very easy to stick. If I did get 71b to stick, I'm wondering if that would be the same issue with MLF not happening.

Basically my plan was to make a cider with some residual sugar left and also lower my TA from 8.5 g/l to around 6.5 g/l. I'm not wondering if that is not possible with 71b. I'm thinking it will go completely dry and lower the acidity or it will stick and keep the acidity about the same. I really have no idea though.

[Francis Bonenfant]

Unfortunately, I cannot test for TA at home and my rickety pH pen is barely accurate within +- 1. I can only ''measure'' acidity through a sensory test and have qualitatively compared the same juice fermented with say, EC-1118 and 71B. The result is noticeably less acidic, at least when fermenting to dryness.   The only batches I have fermented with residual sugar are my 14% alc. dessert ciders. It is much harder to judge if the malic acid has been metabolized, because of the residual sweetness and the impossibility of direct side-by-side comparison (since EC-1118 or other wine yeasts won't suffer an alcohol kill at that same exact %). A titration kit is definitely on my to-buy list for this year... It would be great if you could finish the experiment you have already started and make us a nice total acidity as a function of gravity drop!

[Claude Jolicoeur]

Hello Francis,
Thanks for the appreciation on the book and for starting this interesting thread...

Le mardi 8 décembre 2015 17:47:20 UTC-5, Francis Bonenfant a écrit :

I've been making cider and mead for a few years now on an homebrewing scale, using mostly unfiltered juice bought at farmer's markets. I have experimented with many of the most well known yeasts before settling on Lalvin 71B for most of my batches. The malic acid metabolism is nice, I find that it simply produces better tasting brews than champagne yeast, and it stops at 14% alcohol even in a nutrient-rich must, which is nice for sweet dessert ciders and meads.

About the 71B yeast, note that it is a killer factor sensitive strain. This means it will have more difficulty to establish itself as the dominant strain. In an article by Tredoux et al (http://www.sasev.org/journal-sajev/sajev-articles/volume-7-2/), it is said that if there is 2.5% of the yeast population that has the killer factor while the rest of the population is sensitive, the strain that has the killer factor will become dominant.

So, in practice, if you want to make sure the 71B does dominate a fermentation, it is quite essential to sulfite the must prior to yeast inoculation.

 

My first question is about the low temperature behavior of 71B (and other commercial yeasts)

According to Rémi Bauduin (Guide pratique de la fabrication du cidre), between 7 and 15C, the fermentation speed is approximately proportional to the temperature, meaning that at 7.5C, the FSU would drop to half of the value it had at 15C. Now, this can't be exact for all yeast strains, but is probably good enough for a first approximation.
What I don't know is if this applies also to the growth rate, or just to the metabolization of the sugars once the population is established...
 
For my part, I use the 71B relatively often (at least one batch a year), and my fermentation room is at the moment at 10C, it is usually around 13 or 14 in October as I start my fermentations, and may go down to 7 or 8 during the coldest months. Never had an issue at these temperatures. But yes often slow ferments...

My second question is about pitching rate.

I do pitch at less than 25 g/hL when I want a cider to stick.
You have to keep this in perspective...
Biomass contains approximately 10% of nitrogen. If you pitch 25 g/hL, this is 250 mg/L or 250 ppm of biomass - of this there is 10% or 25 ppm of nitrogen. You may compare this figure to typical YAN (yeast assimilable nitrogen) content of juices, that may run between 50 and 150 ppm. Hence, if you have a low nutrient juice, yes adding a full dosage of yeast will increase noticeably the nitrogen content of your must.

If you look at this from another perspective, assuming your must contains 100 ppm of YAN, this is 100 mg of N per L, and this will permit growing a maximum of 1 g of biomass per L. Add to this the pitched yeast, you get 1.25 g/L of biomass. And you may assume the speed of fermentation is proportional to the biomass when all other things are equal - so an increase of 25% of the biomass would cause the same increase in speed of fermentation...

But you also need to keep in mind the other factors that Andrew mentioned earlier...

Claude

[Nathan Shackelford]

Just another personal experience... I fermented only 5 gallons with 71B this year with a must that was somewhat tart at 3.2-3.4. I found that fermentation proceeded very slowly at 55 degrees F. In fact, other wild fermentations and wine/champagne yeasts were progressing much more quickly. Mid-ferment I tasted the cider and it came across as slightly less acidic when it was in it's slowest phase of ferment. I worried that it would stick at a high gravity unless I warmed it up. I looked up the ideal temps for the yeast. When I closed the cellar window and got the temp to 60 degrees F., it sped things up and it went all the way to dry by 30 days. Upon tasting, I felt the cider was more tart than before and possibly more tart than some of the other batches fermented with wild or other wine yeasts. I'm aging it on the lees right now, knowing that it may encourage MLF. It's not really the best time to be making a final comparison, since there are still so many changes taking place, but that's my experience so far with 71B and low temp.

I did not sulfite this juice, so it is also very possible that this ferment has been taken over by native yeast, and fermenting at a lower temp without sulfite may have helped that to happen. I will test pH when I rack and it might reveal more info. 

[Richard Anderson]

Interested in the killer factor sensitive concept. I have over the years used several yeasts in a single batch , including 71 B without thinking much about it. I have thought about one yeast overtaking another but somewhere along the line but was assured that it was no problem. I looked at the reference given by Claude and could not quite a get my head around it.

[Llanblethian Orchards - Alex]

Hi, just to say I agree with Andrew on the lower pitch rates, you are risking allowing wild yeasts to do their thang.

Personally I add sulphite at the wild yeast kill ratio, wait 48hrs then pitch wine yeast and I will use 1 sacket per 6 - 25 gallons. If I add one to 25 gallons im using a 1/4 of the desired amount, but personally im not too worried about some wild yeasts in there as long as there is some form of fermentation. If I need to do any more I will just tip a cider that is already going into the new barrel as a starter.

Alex

[Christina S]

Hello. I am a new cider maker but experienced brewer. This discussion reminded me of the British/Fuller's beer fermentation schedule, which seeks to preserve esters. I am not sure this is helpful, but here it is:

1.) pitch at 17C (62.6F)

2.) let free rise to 20C (68F) over first 8-12hr

3.) hold @ 20C (68F) until half way to FG

4.) decrease to 18C (64.4F) until 1/4 or 1/5 is left (that is 3/4 or 4/5 of the way to expected FG), then chill to 6C.*

*Yeast don't work at 6C, and that is the point. You want the yeast to stop working just as fermentation is complete, and not a moment longer, so the yeast don't start cleaning up the esters (the Fuller's ale yeast will complete fermentation as is cools from 18C to around 16C, beyond which it goes to sleep and drops out of suspension). That is why you have to force carbonate. The method is not compatible with carbonating in bottles.

Anyway, this method could perhaps be adapted to the temperature range of whatever yeast you are using, I suppose? Cheers! -Christina.

[William Grote]

Christina...

Very interesting point about preserving esters rather than letting the yeast clean them up, having starting in brewing as well, we follow fermentation procedures to discourage flavor faults in beer that might actually be desirable in ciders. 

Francis...

There are some excellent wine yeasts that you will not find in any homebrew supply store that are specifically selected for colder temperature fermentation, think of these as fruit specific lager yeasts, and kudos on pointing out the misinformation new cider maker often face by seeking advice in the brewing community, I learned the hard way for my first 2 years of cider making, following the same bad advice in the 'cider' sections of beer forums, (don't even get me started on the abomination they call Apfelwein, having live in Frankfurt am Main for 10 years I can attest that Goethe is rolling in his grave)

Back to yeast, Scott Labs has great information on their website, and recommends a few strains for cider, notably R2, DV10, BA11.  I have been using R2 which lists 50F as well within its lower range, and pitch 1g/gallon, rehydrated for 15 min at 102F, at cellar temp, which is 62-65F then the next morning I move the fermentor into a keezer kept at exactly 50F.  I find that I get vigorous fermentation within 24 hours and no SO2 production with this yeast, temp combo, rather, an incredible vanilla / oak like aroma that fills the cellar.  I have experiment with lowering the temps to 40-45, and find this will stress the yeast and give off SO2, but will certainly still ferment.  Back at 50F,  it usually takes 3 weeks to hit 1.030 then another 4-6 weeks to get down to 1010, at which point I rack and move the carboy to my 'cooler' room, which is an IoT / WeMo / Inkbird controlled insulated corner of the cellar, and is a pretty steady 52-55F, depending on the outside temperature swings.  I find my ciders are very aromatic and flavorful following this procedure, even as they hit terminal gravity at 1000-999. 

[Christina S]

Very interesting William. So far I have only made a handful of one gallon batches, all with 71B fermented 66-68F, with nutrients. I want to give this cold fermenting thing a try. I looked at the low temperature tolerant yeasts in the 2015 Scott's Cider Handbook and the ones I can get locally are BA11, 1118, 1116 (I can also get 71B and D47, but they are not as tolerant of low temperatures). I am unsure how to choose between the three. It would seem desirable that the yeast be a low sulphur producer, is that right? That eliminates 1116. BA11 has high nitrogen needs, whereas 1118 has low. Which is better? I will be using apples from my own 150 year old, unfertilized trees. I would not mind if the yeast got stuck and stayed a little sweet, so would BA11 be better? Or would the low nutrients in my juice cause it to produce sulphur? In order to maximize ester production I was thinking of doing a modified Fuller's schedule: pitching at 63F, letting it rise to 68F, holding it there until halfway through fermentation, and then dropping the temp to 55F (my cellar temp) over several days and holding it there for the remainder of fermentation. How does that sound? Thank you in advance for your advice. Cheers! -Christina.

[Andrew Lea]

On 23/03/2016 00:09, Christina S wrote:
>
> I want to

> give this cold fermenting thing a try. .....I will be using

> apples from my own 150 year old, unfertilized trees. I would not mind if
> the yeast got stuck and stayed a little sweet,

In view of your professed objectives, might I suggest that you don't use
a cultured yeast at all? Try a (sulphite-directed) wild yeast
fermentation. That's what many or most of us do here in the UK and it
works just fine. No complicated temperature strategies required. Just
start things going in autumn and be ready for your first racking in
spring. Looks after itself and H2S production (despite what the
'experts' will tell you) is usually minimal. Wild yeast fermentations
keep going down to 4C. If you have a very cold winter climate you may
need some protection against prolonged sub-zero freezes but otherwise
it's pretty much 'fit and forget'! If you are lucky and your trees are
really low N and you are clever with your racking you may well get it to
stick slightly sweet.

Andrew

--
near Oxford, UK

[William Grote]

Morning Christina

If you are so lucky to have such trees, I would certainly try to do as Andrew suggests.  I admit to having arboreal envy, (living in the middle of Boston) the only old apple trees available to me were some fantastic crab apples in front of the Federal building, and I was 'denied' my request to harvest them last fall.

But back to your question, cider is very different from beer, first off, you can literally do what Andrew mentioned and 'set it and forget it' for 6 months ( with a few rackings, if you wish, to try to keep some of the sugars ) but the schedules that beer brewers follow are completely unnecessary for cider as the fermentation time frame is geologic in nature when compared to beer.

Let's take the 10 days of a typical beer fermentation and put it in a cider scale perspective ( with a nod to David Brower's 'Sermon' where he takes the history of Earth and replays it as the 6 days of Genesis, I wanted to do this in reverse order with Cider to Beer, but I'm not that creative, so hers is a blunt comparison 

Beer

Day 1 -2 pitch low temp and free rise, yeast growth, phenol production

Day 3-7 fermentation underway, temp control critical for esters and reducing fusel alcohols 

Day 8-10 bring the temp up for a diacetyl rest to clean things up and remove any acetaldehyde 

Bottle

Cider

Day 1 Dose with K-meta for a partial kill and wild yeast fermentation or pitch a cultured yeast

Day 2 - 120  Check occasionally that your airlocks don't dry out

Day 121 - 180  As temps rise naturally in the spring, you might get some MLF going to soften things up 

Bottle

Of course, you can bottle and drink cider earlier than 180 days, it just won't be quite as good.  

The point is, beer is on a very different schedule than cider.  Where a brewer is like a chef, and can control countless variables in the wort which can be further manipulated by a strictly controlled multi- temp fermentation schedule, resulting in even more variation as the yeast eat their dinner at different metabolic rates, the cider maker must make due with the juice that the apples provide and little else, but the trade off, then, is that they need not fret over day to day changes and let the natural swing of the seasons do the rest of the work.

By the way, MoreWine has a clean room, and they purchase the bulk yeast from Scott Labs and break it down into 8g and 80g packets, so you can pretty much order anything Scott makes, from them, without having to buy a 500 gram brick at a time.

[Christina S]

Thank you Andrew and William.....Some day I may take the plunge and do as Andrew suggests, but not this year. It will be my first time making a full 5-6 gallon batch, and I would prefer using a known yeast. I hope to use Mangrove Jack's Cider yeast M02, recommended by a friend. But I am fascinated by the idea of using wild yeast; I can see myself giving it a try in the future.

Cheers! -Christina.

[Andrew Lea]

On 26/03/2016 00:54, Christina S wrote:

>
> When dosing with Campden tablets for a partial kill, how many ppm are
> you targeting?


Conventional pre-fermentation wine or cider sulphiting aims for 0.8 to 1
ppm molecular SO2. The amount of SO2 you need to add to achieve this
depends on (a) the pH of the juice and (b) the amount of SO2 binding
components in the juice. The first you can measure, the second is an
assumption. However, there are reasonable practical estimates you can
make, see here http://www.cider.org.uk/sulphite.html or in my book.

For a part kill, and to preserve some wild yeast character, I would drop
the molecular SO2 to 0.5 or 0.25 ppm. That is, add one half or one
quarter of what the textbooks recommend. But be prepared for a long lag
phase (up to 3 weeks) as the yeast cells multiply to the required level.

[Adam]

I am using Lalvin 71b in some batches (1 200L and 4 60L) that I have left outside to ferment this year due to a lack of indoor space, the juice was pressed in mid October and got going well - I am not worried about a slow fermentation but the weather has taken a cold turn and is down to 4 degrees celsius in the day and due to drop to freezing tonight. What I am worried about is the possibility that the yeast might be killed by the cold - does anyone know if this is a possibility? At a push I can move some back indoors.

[CiderSupply.com]

No, it will be fine. They just hunker down and sleep through it.

Best regards
Chris Rylands

[Christina S]

I read the article Claude linked to and have a question. My understanding from the article is that kill factors in the strains tested are not all that effective below pH 4.2 (or pH 3.7), or at cooler temps (15C), in other words under "normal" fermentation conditions. If I want 71B to dominate, does it follow that there is no reason not to choose it to ferment a partially sulfited must?

The reason I ask is because I have started a little vinegar making business. Last year I used 1116, because it is kill factor positive, and because it can inhibit MLF. I understand that acetic bacteria are very sensitive to sulfites, so I did not use them prior to alcohol fermentation. I have no idea if sulfites added to the must can persist and still inhibit acetic bacteria further down the line, post fermentation. Does anyone know? In any case 1116 fermented out well but I don't think I let it age long enough before turning it into vinegar. I'd like a yeast that matures more quickly, and 71B fits the bill....

Oh, the reason I am thinking about using 25-50% of the normal dose of sulfite is to inhibit lacto bacteria (they say that is not good if you are making vinegar) and wild yeast (because I need predictability, speed, and a clean ferment).

Thanks in advance.

Cheers,

Christina.

[Denis France]

Hear hear Andrew and William.

 

I messed around with different yeasts when I was first experimenting and gave up once I realised other factors were more important, primarily variety and method of processing pre fermentation. 

Denis

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