The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Raisin Yeast Water

Debra Wink's picture
Debra Wink

Raisin Yeast Water

This post is in honor of the current community bake featuring Jeffrey Hamelman’s Swiss Farmhouse Bread. The process begins with soaking raisins in water for 5 to 6 days to create the natural leavening for this bread. Essentially, the long raisin soak is making wine, but from rehydrated dried grapes instead of fresh. Just the first stage of wine fermentation, though. Being higher in natural sugars than most other fruits, grapes are particularly suited to winemaking. But making wine is very different from making sourdough in both the species that are initially present in the raw materials – grapes versus grains – and how their cultures develop over time.

Grape skins, like the bran covering on grains, provide a natural biofilm of microorganisms, most of which have names quite foreign in the baking world. Two of them – Kloeckera and Hanseniaspora – together account for 50-70% of the yeast, with the balance made up of a variety of other genera – Candida, Metschnikowia, Cryptococcus, Pichia, Kluyveromyces, Hansenula... In wine lingo, these flora are collectively referred to as the non-Saccharomyces yeasts. Indigenous strains of our old friend Saccharomyces cerevisiae are also present, but in very low numbers by comparison. And yet, S. cerevisiae is by far the most important.

In the beginning of a typical wild fermentation, non-Saccharomyces yeasts take off. Their initial flush is short-lived, however, and after about the first two to four days of fermentation, they start dying. They require more vitamins than S. cerevisiae, and vitamins are in limited supply; they are less tolerant of alcohol than S. cerevisiae, and S. cerevisiae is a more prolific producer of alcohol; they have a slower growth rate at typical fermentation temperatures than S. cerevisiae, and so are less competitive. In other words, Saccharomyces cerevisiae is just all-around tougher and less demanding. It is a better contender over the long haul, and so it rises valiantly to the top.


Growth Pattern During Alcoholic Fermentation by Species Naturally Present on Grapes

 

 

Note the time line. At four to five days, the Saccharomyces population reaches its maximum, while other yeasts are dropping like flies. Temperature plays an important part in indigenous wine fermentations. Fastest yeast growth and fermentation occur at 77-86ºF (25-30ºC) with a general pattern following the one shown here. Below 68ºF (20ºC), the non-Saccharomyces yeasts don't necessarily die off. Their rate of growth is faster than S. cerevisiae at the lower temperatures and their tolerance to ethanol is increased, so their populations may remain high to the end.

Now take a look at lactic acid bacteria (the orange line). They drop to their lowest numbers after about five days (less than 10/ml), which explains absence of acidity in the bread. Oenococcus oeni is a species of lactic acid bacteria unique to wine ecosystems, and depending upon pH, may be the only one involved. It is the primary agent in malolactic fermentation later in the winemaking process. But lactic acid bacteria don’t take off until about two to three weeks after alcoholic fermentation is complete, giving us a nice window of opportunity to leaven bread without their interference.

While fermented raisin juice provides natural leavening, being primarily Saccharomyces cerevisiae without lactic acid bacteria, clearly it isn’t sourdough. This is the wild counterpart to bakers’ yeast. You may be wondering, "So why bother fermenting raisins if you end up with the same species?" I think you’ll know the answer the first time you bake a loaf for yourself. Wines produced by wild, mixed fermentations have the potential for more complex and interesting aromas and flavors, even if less predictable than those induced by commercial monocultures. And so it seems just as true for breads leavened by them. The fragrance that filled my house the first time I baked this bread had a richness and intensity I had never experienced in a lean bread before, the foretelling of wonderful flavor. 


What it Looks Like in Action

Your timeline might be a little different than this, although you should see bubbling within 48-72 hours if it's working. As always, with variable live cultures, variable ingredients and variable conditions, results will vary.


Day 1

Initially, raisins sink in water and start out on the bottom. Some air bubbles may get trapped in the wrinkles.


Day 2

As they absorb water and swell, raisins expand and appear to be suspended throughout the watery raisin juice, although still underneath the surface.


Day 3

You'll know fermentation is underway when active bubbling becomes evident. The liquid will turn cloudy with yeast, and the raisins migrate upward as they become gassy.


Day 4

As fermentation progresses, the raisins become more buoyant, floating higher in the liquid (above the surface). Excess yeast cells settle in an increasing layer of sediment on the bottom.

 

to be continued ...

DanAyo's picture
DanAyo

Debra, is there an optimum stage (4 or 5 days?) when the S. cerevisiae (desireable yeast) are highest in number and available? Your chart shows all yeast falling off after only 4 or 5 days. It seems after time (2 or 3 weeks) the LAB kick in making the YW less active and possibly more acidic. And that during this same time the S. cerevisiae are falling off.

If my understanding is correct, should YW (if max yeast was the goal) be made on demand as opposed to continual refreshment for longevity? I get the idea that is what Jeffrey had in mind when he wrote the instructions. His formula didn’t call for a lot of water. Does he intend that we make the YW for a single bake and remake a YW for each new bake?

As always, I appreciate your help.

Abe's picture
Abe (not verified)

The only thing I can say is while the fruit is still floating then there is enough yeast activity. And while many just replace some of the water in a recipe with yeast water, Hamelman's way of making a preferment in two stages should build up yeast activity as well.

If you do go down the path of keeping a yeast water and refreshing, instead of starting from scratch each time, then this refreshment will rebuild the yeast population.  By replacing all the water and fruit then using a little yeast water from the last batch will make a new yeast water in next to no time and as strong as a fresh batch.

DanAyo's picture
DanAyo

Like SD starters it seems there are many misconceptions dealing with YW. I was under the impression that the best practice is to use the YW for a bake and then replace that amount of water with new water. Replace the fruit if floating (in the case of raisins).

But your procedure (if I understand correctly) is to use “a little water” (YW) is quite different. Will this method produce the same results as starting from new? My goal is to have the strongest yeast possible at the time of a given bake.

By “a little water” are we talking about a tablespoon or what?

I am often hesitant to pose question that could become controversial. Opinions vary, but I would like to know the truth.

Danny

Abe's picture
Abe (not verified)

As you know Dan there are so many methods. Yes, you can just replace what you have taken and some of the fruit. That'll work. For a while (until I decided it's no issue to make it from scratch each time) I did keep one for a little while in the fridge. My preferred method was to make a batch, keep it in the fridge, dip into it to build preferments and when the yeast water ran low i'd do a big refreshment by just using a little of it in a fresh batch for inoculation. If It hadn't run low but it had been a while since I had used it then I did a big refreshment anyway. Like keeping a sourdough starter healthy.

How much to inoculate a new batch? Well when it comes to yeast water I really don't measure at all. Some fruit in a jar, cover with water and add a little yeast water from the last batch. Within 12-24 hours you've got a very active fresh batch of yeast water. Like making yoghurt or kefir.

Debra Wink's picture
Debra Wink

There's a much wider window of opportunity here than with sourdough. The Saccharomyces is your best bet for strong leavening, and that stays high for some time. This graph is showing that they are still >1,000,000/ml even at 8 days out. That's more than a million per gram for our purposes. And at Jeffrey's 5-6 days it's more like 10+ million. So plenty of yeast to do the job. It's okay (maybe even preferable) to let the other yeasts fall away.

LAB don't start taking off until 2-3 weeks after alcoholic fermentation is complete. And alcoholic fermentation goes on for quite some time. If I remember right, when I was experimenting with them, they fermented for more than a month before the raisins all sunk to the bottom. So I wouldn't worry about LAB.

I think that if you can make good yeast water dependably on demand, then do what's most enjoyable to you. Maybe making it from scratch each time will bring more complexity from the added contributions of the non-Saccharomyces yeasts. Don't know.

But for those who aren't so fortunate, they might prefer to perpetuate once they get one started in order to avoid a repeat of the frustration. This is more likely to yield mostly S. cerevisiae with less of a contribution from the other yeasts because you'll largely be by-passing them. Still, it's a wild yeast, and wild strains produce more flavor and aroma compounds than bakers' yeast. And S. cerevisiae is more robust.

So either way is a win if you ask me.

DanAyo's picture
DanAyo

Debra wrote, “If I remember right, when I was experimenting with them, they fermented for more than a month before the raisins all sunk to the bottom. So I wouldn't worry about LAB.”

Every time I make a YW the raisins sink to the bottom immediately after they are put in. Once fermentation begins they rise to the surface. I thought they were spent after rising.

Question - do the raisins sink to the bottom once again? Is that when their sugars have been exhausted?

 

Debra Wink's picture
Debra Wink

Every time I make a YW the raisins sink to the bottom immediately after they are put in. Once fermentation begins they rise to the surface. I thought they were spent after rising.

They're just getting started :)

Question - do the raisins sink to the bottom once again?

Yes, eventually.

Is that when their sugars have been exhausted?

Well, it's when there is no longer gas production to keep them afloat. Is it the sugars that are exhausted? Maybe. But it could be something else they've run out of, like nitrogen or another nutrient. Or there is too much alcohol, or other substances that become inhibitory. Maybe it's any combination of those things.

DanAyo's picture
DanAyo

Thanks so much, Debra. I appreciate your patience and willingness to help. I am inquisitive.

For me it’s not enough to succeed, I curious to know why...

Danny

Abe's picture
Abe (not verified)

Very interesting. I've never delved too much into the chemistry of it but I definitely agree with you that even though the yeast is of the same species as bakers yeast (i've just learned) the bread resulting from a yeast water has that something extra! The aroma while baking and taste is definitely more intense and flavoursome. Looking forward to the next installment.

Debra Wink's picture
Debra Wink

Abe, yes, the aroma compounds actually help get yeast disseminated in nature, because they attract insects (like fruit flies) which come to feed on them. (Microorganisms are an important part of insect diets.) The microbes that stick to their legs and bodies hitch a ride to the next fruit or flower the insect visits. The most aromatic tend to be spread more, and so it is a trait that is naturally selected for :)

Benito's picture
Benito

Thank you Debra for this enlightening explanation of what is happening microbiologically in our yeast waters.  Brings me back to medical microbiology lectures in university.

Debra Wink's picture
Debra Wink

Have you tried baking with yours yet? It looked like a good one!

Benito's picture
Benito

I put the yeast water in the fridge to keep until today when I finally got the first build started. I hope when I get home this afternoon that it’ll be very nicely risen so I can have the second build working overnight for the final dough tomorrow. 

Benito's picture
Benito

Very surprisingly the first build hasn’t risen at all after 10 hours now since mixing the flour and yeast water.  I’m really surprised because the yeast water is still actively bubbling.  I’m not sure that I’ll be able to fit a bake into my weekend now so it might have to be next weekend unless this suddenly rises now which I’m not expecting.

DanAyo's picture
DanAyo

Ben try putting it somewhere warm. Maybe a heating pad, on top the water heater, in the oven with the light left on.

Something is not right if your YW was active. You said you put it in the refrigerator to hold for a while. What is the temperature of the levain?

If, after trying it doesn’t come alive and you want to bake this weekend, you might try supplementing the next build with a little commercial yeast. Not a great solution, but still a solution.

Danny

Benito's picture
Benito

The temperature of the levain was 80.6ºF.  I’m really surprised that nothing happened, the yeast water was definitely bubbling still even in the fridge and all the grapes were still floating.

I’ve put it into the oven with the light on and we’ll see if anything happens this evening, otherwise I’ll try again next week.

I don’t want to use commercial yeast with this bake, it would feel like it defeats the whole purpose of it.

Abe's picture
Abe (not verified)

If you see some air bubbles then proceed onto the next build and try keeping it warm. 

Benito's picture
Benito

Breaking it open there are no signs of life, no bubbles.

Abe's picture
Abe (not verified)

So how about moving onto the next build but instead of using water use more yeast water. Find a warm spot for the 12-14 hour ferment. If still nothing then proceed with the recipe using some yeast or sourdough starter. Might be good to prep your starter at the same time just in case. Not to worry. We can troubleshoot later. 

Benito's picture
Benito

I actually wondered about subbing yeast water for the water in the second build.  Nothing to lose by trying that, thanks Abe.

DanAyo's picture
DanAyo

Sure would like to know what went wrong with Ben’s first build.

Benito's picture
Benito

Me too, on closer inspection there were a few small bubbles in the first build, nothing like I would have expected though.  Even when my sourdough starter was young it was able to produce more bubbles than that.

So I moved on to the second build and used yeast water instead of water.  Opening the yeast water I could hear the bubbling fizzing sound.  It’s in the oven with the light on, once it is warm I’ll have to prop the door open otherwise it will reach over 90ºF in there as it has two light bulbs.  We shall see if it is active by the morning or even before I head to bed.

Benito's picture
Benito

The 2nd build was very successful.  I left it in the oven with the light on and 12 hours later it grew about 3 times.  It would have been 85ºF in there.  I still don’t know why the first build didn’t work but the second one did, albeit with yeast water instead of water in the second build.  It was the same yeast water I used so strange.

Debra Wink's picture
Debra Wink

I often find the 1st build to be reluctant too. And from the responses you've gotten, that appears to be kind of common. Looking forward to hearing how the bake goes today :)

Benito's picture
Benito

Debra, despite my problems with the first build not rising, using the yeast water instead of water for the second build seems to have worked.  The bread is super tasty and has a lovely pink purple colour.

Thanks again everyone for your help!

Benny

Benito's picture
Benito

Dan, do you think that I needed to stir the yeast water a bit before pouring some off for the first build?  I didn’t do that thinking I didn’t want the debris at the bottom of the bottle going into the first build.  When I built the second with yeast water I decided to mix it up a bit.  I have no idea if that was the difference or it if was the temperature.  My apartment is pretty warm at the moment around 80ºF but the oven with the light on and door propped open is about 85ºF, maybe that was the difference?

DanAyo's picture
DanAyo

I don’t have a lot of experience with YW, so I am no authority. But I didn’t stir mine. Actually, I used a turkey baster and siphoned off the liquid from the middle of the jar.

Hopefully someone with experience will reply.

My YW ferments like crazy @ 84F.

 

ifs201's picture
ifs201

I posted about it, but I think I had a similar issue where build #1 sat out for 9 hours and nothing happened! Was very surprised since my YW seemed really active. I went to bed and when I woke up (approx 15 hours after making build #1) it had tripled! Build #2 and the rest went smoothly after that point. Build 1 just took a really, really long time. 

Benito's picture
Benito

Yes I read about your experience with your first build and remembered it when I checked my first build 8 hours after starting it and again 10 hours after the start and nothing had happened.  The second build certainly worked though but with yeast water instead of water.

ifs201's picture
ifs201

Glad it's working! 

ifs201's picture
ifs201

I posted about it, but I think I had a similar issue where build #1 sat out for 9 hours and nothing happened! Was very surprised since my YW seemed really active. I went to bed and when I woke up (approx 15 hours after making build #1) it had tripled! Build #2 and the rest went smoothly after that point. Build 1 just took a really, really long time. 

julie99nl's picture
julie99nl

My first build did show activity, but it took hours and I had it in my proofer at 31C/87C.

dabrownman's picture
dabrownman

I treat my two YW's, Fig and apple. the same way as I treat my NMNF rye sourdough.  It stays in the fridge for months at a time with no maintenance up to half a year.  When I remember it is in the bottom back of the fridge I get it out, drain off the liquid and toss all but few fig or apple pieces that sunk to the bottom months and months before,.  I wash the jar, put new fruit in, put a couple of the old fruit pieces in and 3 T of the old liquid - making sure get some of the cloudy gunk from the bottom and fill the rest of the re-purposed 14 OZ plastic peanut butter jar 3/4 full with RO water.  I put it on the counter and shake the jar every 4- 6 hours for 24 hours and by then it is fully refreshed and ready to go to work.  I make a loaf of bread with it and then back in the fridge it goes for another 4-6 months.  Have been doing this for years now - at least 5.  Like SD, these wee beasties are impossible to kill!

Happy baking Debra

Debra Wink's picture
Debra Wink

I was wondering where you were. I know yeast water is a favorite of yours.

Happy Baking to you as well :)