Yeast Is A Hot Commodity; Brewing And Breadmaking During Lockdown

In the recent frenzy of stocking up with provisions as the populace prepare for their COVID-19 lockdown, there have been some widely-publicised examples of products that have become scarce commodities. Toilet paper, pasta, rice, tinned vegetables, and long-life milk are the ones that come to mind, but there’s another one that’s a little unexpected.

As everyone dusts off the breadmaker that’s lain unused for years since that time a loaf came out like a housebrick, or contemplates three months without beer and rediscovers their inner home brewer, it seems yeast can’t be had for love nor money. No matter, because the world is full of yeasts and thus social media is full of guides for capturing your own from dried fruit, or from the natural environment. A few days tending a pot of flour and water, taking away bacterial cultures and nurturing the one you want, and you can defy the shortage and have as much yeast as you need.

More Than Just A Supermarket Product Line

CIdermaking, chez List. Natural yeast ciders can be tricky to get right, so I usually cheat and add a champagne yeast culture.
CIdermaking, chez List. Natural yeast ciders can be tricky to get right, so I usually cheat and add a champagne yeast culture.

Everyone enjoys the odd crusty loaf or foaming pint. The yeast that make this possible is an interesting technical subject in its own right that makes a significant entry into the hacker community. There’s a lot more to it than just the sachets of baker’s yeast in the supermarket ingredients aisle and if you know what you’re doing you can snag it out of thin air.

Yeast cultivation is a subject in which I have more than a passing interest, because ever since I was a teenager I have made my own real cider. For years the quality of the yeast that ferments my juice has been of great concern to me, sometimes it’s gone wrong and I’ve gone to considerable lengths in other years to ensure I have the right strains.

Yeasts are single-cellular fungi, and just as with any other class of organisms there are many varieties present in the wild. Some can be found widely, while others are specific to particular environments or situations. Finding them is easy enough, they are so widely dispersed that they are present in some form almost everywhere, and the air you breathe probably contains significant numbers of yeast spores which are the source of some of the natural yeast cultures shared by those people on social media. I’m no expert in species taxonomy, but the type of yeasts we are interested in all belong to the Saccharomyces family, which the sharp-eyed will recognise as containing the Ancient Greek words for “sugar” and “fungus”.

The Hackaday Strain

The Hackaday Strain, showing some early promise of cloudy yeast.
The Hackaday Strain, showing some early promise of cloudy yeast.

Thanks to a liking for home-made pizza, we already had a pack of dried yeast in our cupboard here. But what if we hadn’t? It was time to put all that natural yeast cidermaking experience to the test. Into the store cupboard for some dried fruit and plain flour, and into the recycling bin for a jam jar with a lid. This was cleaned with some boiling water, and then a spoonful of currants were shaken up in it with some water. Immediately I could see some yeast had come off the currants, because the water was cloudy.

The process of turning cloudy currant water into a usable yeast culture is a slow and annoying one. The idea is to mix it up with some flour to serve as food and put it in a warm place, then once you can see the tell-tale bubbles and yeasty smell to indicate it’s started going, separate a small quantity of it with some fresh flour and water to make a new culture in a new container. Doing this several times over is designed to produce an environment that favours the yeast and reduces the chance of any bacterial cultures taking hold. It’s slow because wild yeasts take their time to get going, I’ve had wild yeast ciders that have sat for several days before fermentation kicks off.

Eventually though, if you are persistent you’ll have a big frothy mass of yeast that you can feed with sugar just as you would if you were activating dried yeast for baking or brewing. At the time of writing the Hackaday Strain is on its second new culture, and is starting to look as though it  might have enough in it to be used for a pizza later in the week. A Core i7 desktop computer running Folding@Home provides plenty of warmth to incubate it. It’s important to point out though, that whatever yeast you might culture in this way will be a random variety depending on whatever you used to start it. If you’re lucky it’ll produce amazing bread and fine wines, if not you might need to give it another try.

Let’s Get Down To Varieties And Strains

An electron micrograph of Saccharomyces cerevisiae. Mogana Das Murtey and Patchamuthu Ramasamy / CC BY-SA 3.0
An electron micrograph of Saccharomyces cerevisiae. Mogana Das Murtey and Patchamuthu Ramasamy / CC BY-SA 3.0.

The yeasts that you will capture if you create your own culture are likely to contain more than one variety, but the commercial yeasts you buy will have been carefully grown as a monoculture. The yeast used in baking, in brewing ale, and in wine and cider making are all different strains of the same variety, Saccharomyces cerevisiae, which is a yeast that thrives at a higher temperature. Thus when you make bread you leave it in a warm place for proving, and when you brew an ale you will warm the wort slightly for the best result. In both cases the fermentation is anaerobic resulting in the production of alcohol and carbon dioxide, and when it is in a liquid it floats to the top. thus ales are sometimes referred to as top-fermenting. It’s possible to brew ale with baker’s yeast, and though I’ve never done it, it’s no doubt possible to make bread with the corresponding beer strain.

Get your Saccharomyces pastorianus products, at Hackerbrau Munchen!
Get your Saccharomyces pastorianus products, at HackerBräu München! Jebulon / CC0

So having identified the protagonist in the making of both bread and ale, we might consider ourselves to be done, right? Perhaps some of you have noticed that I’ve used the word “ale” so far rather than “beer”, because of course top-fermenting ale is not the only type of beer. The word “lager” is rather misused in some English-speaking countries to mean a beer in the pale Pilsener style, but in fact “lager” from the practice of storing the brew in caves to mature, refers collectively to an entire class of beers fermented with an entirely different yeast variety. Saccharomyces pastorianus is a natural hybrid between Saccharomyces cerevisiae and another wild species, and ferments at a much lower temperature with the yeast settling to the bottom of the wort. These bottom-fermenting beers come in every bit as diverse a range of styles as their ale equivalents, leaving the mass-market “lagers” such as Budweiser or Carling a poor representation.

There is a third type of yeast culture that is commonly used in the making of bread, so-called sourdough. This is a mixture of yeast, usually Saccharomyces exiguous, and lactobacillus, yielding a fermentation that produces the lactic acid that gives the sourdough loaf its characteristic flavour. This yeast is tolerant of acidity, whereas Saccharomyces cerevisiae would die in the same situation.

I hope that this short introduction has given you a basic primer in the world of yeast, and that if you’re stuck for something to do while on lockdown you can at least try your hand at bread or beer without having to find a yeast sachet on those empty shelves. I didn’t have any hops, so I’ve got a batch of something new to me on the go: spruce ale.  Good luck with whatever you try, and enjoy the fruits of your labour!

Header image: Jon Sullivan / Public domain.

69 thoughts on “Yeast Is A Hot Commodity; Brewing And Breadmaking During Lockdown

  1. I have had a sourdough starter for some years. I also started a culture of commercial rapid-rise yeast a week or so ago. I have a pH meter arriving today to make sure the rapid-rise culture is acidic enougth to keep nasty stuff from growing. The sourdough culture makes its own acid and alcohol, which keep anything harmful from growing. Since the rapid-rise culture did not start out with lactobacillis, I am supplementing it with citric acid and intend to keep the pH in the range of 4-4.5 . I also stir it every day to get some oxygen into the culture. Botulinus wamts an anerobic environment and pH greater than 4.6, so definitely trying to avoid that.

    The commercial yeast culture will mutate or be driven out by natural yeast eventually, hopefully commercial dried yeast will be available again by then.

      1. It is a lot like sour mash whisky, where you take some of the mash from the last batch to start the new batch, ditto with sourdough bread, only you save a little bit of dough from this batch to seed the next. You can start with commercial yeast or buy a commercial starter or get some free starter that has been around forever from the good folks at I have done all 3. If you live where it is cold out you may want to build a proofing box. In the old days you could use a gas oven with just the pilot light on but that kind of oven is getting rarer and rarer. I built a wooden box that will hold 3 2 pound bread pans with room between them and around them, and has a metal grate they sit on. I have a 60W light bulb below them. I threw in a $14 eBay temperature controller, but it is not really necessary, though it does give the project a nice high tech look.

        Also, when you get into baking if you like a more interesting crust, look for recopies that start at a higher temperature and perhaps include putting a shallow pan of water in the oven for added humidity.

      2. Mike, it’s very simple. When it rises to it’s maximum you take a chuck from it, throw it in clean container or a plastic bag you’ve used once for food and washed it out

        (Sidenote: bake sale – they made great cookies but they used the dollar store ziplock bags and dumped them directly hot into the plastic bags. In short it tasted like how a 35 gallon garbage smells. It was a bake sale at UPS corporate.)

        Just throw it in the uncooked dough in the fridge. That is it. Even if fridge gets frozen/ freezing, the yeast goes dormant and even if the outside looks terrible just cut off what looks bad to Once you take your half pound source, you will always have more to replenish it. Take another chunk. You don’t throw away old moldy cheese you just cut off the mold.

        (Most of the time if it’s on dairy or flour products and its green mold… well you know the rest.)

        1. I think there was a famous bread making company (white and orange bags) in S.F. or N.Y. that used this exact technique to replenish their exact blend/brand/ strain of sourdough. I remember very clearly that documentary. I think it was an Ep on Good Eats.

      3. One of my cookbooks (the aptly named How To Cook Everything) has some notes on starting and maintaining a sourdough culture which IIRC used commercial yeast instead of waiting for wild yeast to land in the bowl. I’m tempted to try that now that there’s stories of yeast shortages, but the culture seems to need daily maintenance.

        1. sour dough does not require daily maintenance I use mine once a week and put it in the fridge it can last about 2 weeks, but I cook a lough each weekend you do need to feed it but I do this only when using it. There is loads of information around on the web on doing your own sour dough, its not difficult to get one going took me about a week.

      4. I started a sourdough culture a few weeks ago following King Arthur Flour which started with unbleached whole wheat flour and water, then feed a few times a day with equal parts by weight of AP flour and water. No yeast needed.

    1. if you want the acidic safety of sourdough starter, rapid rise, and no actual sour flavor, you can add a small amount baking soda when mixing up bread or pancakes. It will rise faster than plain sourdough starter, neutralizing the acid and sourness in the process.

  2. Your instant pot makes a great dough proofer. Set it on Yogurt, and use the “-” button to get the “less” light lit, and it will proof at about 85 degrees F. Pour a little water in the bottom of the pot to distribute heat, as the heater is in the center. Put a trivet over that, or a plate, as a spacer to keep your dough out of the water. Line the pot with parchment and spray that with oil, or just use a bowl. Even slow sourdoughs will fill the pot in about two and a half hours, commercial yeasts will rise within the hour.

        1. Well the basic white is well, white and basic. Depends a little on your machine, some of the vertical ones whatever you do seems to come out like a steamed loaf. The more horizontal pans, you get a tall loafy loaf and better crust. But there’s plenty of different bread recipes for them, oat and wholemeal and nutty stuff and fruity stuff…

          However, you can just use it as your mixing/proofing robot and bake cottage loaves or plaited loaves or tin loaves in the oven with the dough.

        2. Well a busy person needs to use the means at hand. While the bread machine is doing it’s job, one can be doing other chores. often puritanism can be useless, when it serves no real purpose. In the event a bread machines is lame, is a modern kitchen rage Lame? Is package flour lame?. Thing is that road is like traveling on a Möbius surface.IMO practicality is never lame.

  3. FYI: to make alcohol in Poland (even beer) you must have a registered company and pay excise tax depending on alcohol content of whatever you’re brewing. Otherwise even a posession of brewing equipment is enough to land you a couple years in prison.

      1. Did it get re-illegalised?? I seem to recall it became legal for personal use still sometime in the 90s for some reason, law reforms or something, but remained highly illegal to distribute the product (even give away). There was some question/discussion on newsgroups of how big a still you could have until they just assumed you were gonna distribute.

        1. >for some reason

          Fall of the Soviet Union – they couldn’t stop it. Every country bordering the eastern bloc went into major economic downturn because of the collapse of exports to the soviets. People started using “turbo” yeast to turn out 20% ABV home “wine” since it ferments in 2-3 days and distilling it to rotgut vodka using anything available. A coffee maker is quickly turned into a desktop still.

  4. You don’t need to go through the trouble of currant water to get yeast: you can begin right from the flour alone. Keep it around 30C and weed & feed every 8-12 hours to promote the fast-growing symbiotic culture, and in a few days you have a perfectly suitable sourdough starter that’s also by definition happy with your flour and also doesn’t need sugar (the symbiotic lactobacillus in it provides that from the starch). When you add the sugar to make the bread, the yeast part takes off and does what it does.

    I’ve made bread with brewers yeast in a pinch, right before I realised I don’t need to (see above paragraph).

    I’ve also attempted wine with bread yeast, again in a pinch. After the first taste I distilled the whole batch and made a few litres of vodka :-)

      1. With a name like Paul, people become immediately suspicious.

        And by the way, sourdough rules. I am going for sourdough pancakes tomorrow morning. Once you have sourdough going it self replicates as long as you take care of it! I don’t feed mine for 2 or 3 weeks at a time,
        and keeping it in the refrigerator, that works just fine.

        1. With a name like Paul, people become immediately suspicious.
          Or maybe somebody got their knickers in a twist over a comment I made last week and now clicks “Reports comment” on every one I make just so I get automatically flagged for moderation.

      2. I’m seeing a lot lately hung up for no discernible reason. Nearest I can figure, anything with 2 urls does it for sure, anything with 2 or 3 non-standard English words seems to as well, which can mean a lot of tech terms. Sometimes length seems to trigger it.

    1. I have no experience, but going by an episode of Modern Marvels, the yeast used to make wine grows on the skin of the grapes. simply crushing the grapes introduces the yeast needed for fermentation.

  5. haha i just started brewing beer again 3 weeks ago becauae the borders to germany (cheap beer) were closed:)
    does anyone know if i can multiply the yeast with sugar (+yeast nutrient) instead of malt sugar? feels stupid to buy yeast if you can just multilly it.
    and does yeast die or just hibernate if the maximum alcohol level is reached (accidently having a lager with 1.065OG now
    thanks for the article!

    1. I have two cultures going at the moment, one is baking yeast started from a small amount of dried yeast.
      Second one is beer yeast, recovered from some real ale (our stuff in the UK is usually live).

      I top them up every day with a teaspoon of sugar, but with the baking culture I also take half off every couple of days to do the baking, and then top up with boiled and cooled water, and a spoon of sugar.

      I found with the baking yeast it stops working with very low alcohol content so you have to keep splitting the culture.
      The brewing yeast is still multiplying after 2 weeks so yeah, give that a go Kalle for your infinite supply. If you put a winemaking airlock on the bottle you can keep the nasties out. And the cork won’t blow off (mine just did!)

      1. Last week I just found a bottle of localish IPA that was live and it may have used a wine yeast or hybrid because it was meant to be a strong one at 6.5%… now, when I say found, it was 4 years old, been sitting in the basement that long, and it was unfiltered and live I guess, I thought “Meh, IPA, what are the hops for if not for keeping it, can’t go out of date…” so I drank it… the cap came off with a pop and it foamed a lot, very fizzy… tasted it, wow, was like barley wine or malt liquor, think it had gone to 10% in the bottle LOL just had the one and it sat like it was 3 beers worth.

        1. When “White Shield” was ended in the UK I bought up all the bottles I could and left it in the cellar, like yours the last one after a few years was very mature. Did you get he sediment livened up again – add lukewarm boiled water and sugar to it…

  6. If you leave a piece of uncooked bread in a bag in the fridge you have unlimited yeast.

    Abstain from trying to cultivate random yeast. Again do NOT start cultivating yeast. It shares many characteristics with Molds and Funguses.

    If you have lack a very clean environment, a bad sense of smell and microscope.

    Just because it makes water with high flour content bubble and smell funny OR water with a high sugar content cloudy or starts doesn’t mean it’s yeast.

    It could be a bacteria (safe bacteria are somewhat common) if you are sure of it’s source. You can make kefir or buttermilk and yogurt with powdered dry whole milk or whole milk) Kefir and Buttermilk typically has a long shelf life because of the fact it had gone bad once.

    (I am uncertain and don’t know if they pasteurize the milk dairy product before or after. I remember my Grandparents and my parents making cottage cheese and even Mascarpone (its heavy cream that is both cottage cheese and churned like butter, if I remember?))

    FFS Amoeba brain infections happen and they are deadly. And THAT is a single cell organism.

    Forget the Neurotoxins (or the ones that damage your liver or kidneys) that are present in Mold and Fungus, Bacteria cannot be “cooked” out.

    Botulism Poisoning / Botox is still a real threat.

    If you are desperate for “yeast” a bottle of unfiltered/ cold filtered may have some remains.

    If you have one packet of quick rise. Remember the yeast is aggressive enough that you only a 1/4 of the package.

    Self rising dough from “Frozen pizza” and other uncooked goods aka pizza supermarket pizza are enough to get the correct yeast.

    They even have “self rising” flour that contains some yeast but also contains an inhibitor to keep it from replicating. (You take a small piece and add it to normal flour.) Again, you just add it to regular flour.

    If anyone has a Mom, Grandmom, Aunt, Uncle, Father, Grandfather who know about baked goods consult them first!

    1. I think you have it backwards, you can cook out the bacteria but a large number of the toxins don’t degrade at normal baking temperatures. Live botulism bacteria aren’t particularly harmful to a healthy adult, stomach will kill them, but, if they’ve been breeding in anything for very long, they’ll have made enough of the toxin in it to be very harmful.

      1. C. botulinum cultures need 121°C for 3 minutes to be killed but the toxin is denatured at 74 – 80°C depending on strain and time of exposure (5 minutes at 85°C).

        Properly baked bread gets to ~82 – 99°C+ at its center depending on the type of dough and bread inclusions – you can use a remote thermometer with the probe at its center to get very well-baked bread this way.

        More info here (commercial site I have no affiliation with):

        1. Ah yes, and that’s why you have to pressure can peas and beans, gah. I seem to have basic microbiology and food preservation stored on opposite sides of my brain and the connections in the middle get co-opted for something else. Or my mansion of the mind has had a few doors wallpapered over and I have to go up the back servants stairs and through the butlers entrance to get to crap now.

  7. I love yeast, anything that can piss alcohol is a friend of mine. Interesting thing about the raisins though, I remember reading about some archaeologists reading some Babylonian tablets which had a recipe for beer and it mentioned adding raisins, and because none of the archaeologists were amateur brews they couldn’t figure out why the Babylonians were adding raisins to the beer.

  8. Months without beer would be dark times indeed. Fortunately, had lots of brewing kit and no time before the lock-down. Now saving on commute has allowed time to brew. Got a wee bit carried away and shall be drinking quarantine beer for a while. Obviously can’t share it.

  9. Making sourdough from wild yeast is incredibly easy, not that you’d know that from reading on most websites. There is a sourdough cult that likes to make it sound insanely technical. There is a lot of technique, but anyone with a little patience can get passible bread in the first try.

  10. One of the side-benefits of this lockdown has been being able to enjoy a mug of my homebrew cider whenever I want! My first 5G batch from 2019 is kegged and carbed. That one fermented without any commercial yeast and came out very nice!

    I haven’t done much with yeast cultivation yet. I’ve made a fruit bread using cider lees to make the starter, and that came out great. I tried freezing yeast before. That failed.

    One thought about sourdough starters – you could try raising the acidity to prevent bacteriological infection. I always adjust my apple juice before brewing. Fuji apples taste and store great, but like most dessert apples, don’t really have enough acidity for cider. I add malic acid to bring the pH down from 3.9 (borderline risky) to 3.6. Most tap water is just the wrong side of pH7.0. Since you’re only waiting on your starter for a few days, not months, you probably wouldn’t need to make it that acidic.

    I also add tannin powder, and malt extract (as yeast nutrient) to my juice. Obviously the tannin would have no use in the bread starter. I wonder about the nutrient…

    1. I do everything I can to *avoid* acid in my apples, but then I’m aiming for a West country style cider with plenty of tannin. I have a Dabinett tree which is a near-perfect cider apple.

      I use a commercial yeast nutrient. In effect it’s a nitrogenous fertiliser. You don’t want cider without nutrient, it smells of bad eggs.

  11. Tip – you can use ale barm (the yeast sludge at the bottom of the beer/cider fermenter) to make breads, but don’t use bread yeasts to make beer. You’ll be disappointed if you do. OTOH if you’re brewing, you’ll never be short of bread yeast.

    Re: cider – I make dry cider from a kit of concentrate, but a friend once said it was too dry, so I experimented with adding a litre or so of unfiltered pear juice – very nice! No complaints since.

        1. Same here… I found that the easiest way to ameliorate a too-dry cider or alcoholic ginger beer is to just add a dash of really cheap supermarket-brand lemonade (“Sprite” to the americans – fizzy sweet soft drink :-D)

          I experimented with unfermentable sweeteners (e.g Stevia) but even though they made it sweeter, the mouthfeel was all wrong. I suspect the palate isn’t fooled if there aren’t a similar level of dissolved solids.

          Commercial cider makers can filter all the yeast out and add sugars after fermentation, but that’s hard to do reliably at home. Exploded bottles are no fun.

          Another option that I haven’t tried yet is to use a “lazier” yeast that doesn’t quite ferment out all the sugars, or, as mentioned above, add some malt extract or similar to increase the dissolved solids and fix the mouthfeel.

          1. IMO stevia could ruin the mouth feel of anything from horsedung to hydrochloric acid.

            There’s some sweeteners that I think would actually kill yeast off, xylitol if I’m not mistaken.

          2. Thanks RW, I’ll add xylitol to my list of sweeteners to try.

            My beer brewing friends suggest making a really thin lager (think Bud Light or similar, that homebrewers usually love to complain about) as a base for alcoholic ginger beer. The ginger would overpower the “beer” flavour but the malt etc in the beer would improve the mouthfeel…

  12. I’m jealous of your Dabinett. That’s on my list of potential garden additions. A good West Country Scrumpy is tough to beat! Have you ever measured the pH of the raw juice?

    Dessert apples make for difficult cider. I learned a trick this year – I pressed the peels and cores from the apples that were processed for pies and sauce. It definitely helped with the tannins. I have a crab apple to help balance the juice, but it’ll take a couple more years to really start producing.

    I really want to plant a heirloom cider variety or two. Ashmead’s Kernel needs no introduction and will grow well here in Massachusetts. Roxbury Russett originated 10 miles up the road so would be appropriate. Harrison Cider Apple probably has a distant family connection, and Dabinett would be easy to grow and a good producer. Kingston Black completes the list.

    I’m also considering adding a Bramley (for both cooking and juice balance reasons). I might have too many apples by that point. The Fuji is a heavy biennial bearer – I fermented 24G in 2019, and that’s after storing 2 crates for eating, freezing 20 pie mixes, and canning 16 quarts of sauce and 2 quarts of juice. Harvesting that is a lot of work already. I might have to start selling or donating some in the future, especially if the Cox’s Orange Pippin ever establishes itself to vigor (it’s not best suited to the climate). I’m thinking about an espalier or cordon of dwarf-stock trees to limit the volume and increase the variety.

    Tough decisions…

  13. I had a reply in here but apparently I moved on before it was swallowed…

    Some thoughts..

    Sourdough is a lot like sourmash for whisky. You save some from the current batch for the next batch and so on and so on. It is not hard to make your own from scratch, and occasionally you will wind up with something really outstanding. In college I started baking for myself, and than for the girl next door, and than for the people down stairs and before too long it became a pretty major activity. I had a really good sourdough.

    If you don’t want to roll your own you can buy starts on eBay or send the folks at a SASE and they will send you a little packet of starter you can grow. They trace this starter back to 1847. It is very good and kind of a fun piece of history even if you don’t enjoy baking.

    You have to watch self rising flower. In the US it is usually baking powder based, not yeast based. Also, another US ism is Cider is the juice from oxidized pressed apples, hard cider is fermented cider. Cider will almost always ferment on it’s own. I don’t drink, but I do enjoy it in it’s very mildly alcoholic “fizzy” stage. FWIW you can freeze sweet cider for a long time and it still thaws out to be amazingly good.

    Also, if you bake a lot, you will probably want to build or buy a pfoofer. I made mine big enough to hold 3 2 pound loaves. Simple wood construction and about the same footprint as my microwave (which sits on top of it). I have a metal grate about half way from the top to the bottom and an incandescent lightbulb is my heat source. I put in a digital temperature controller but it really did not need it. It just makes it look high tech with a display like the microwave.

  14. OTSO acidity, beer yeast can tolerate acidity as well. After all, the bittering hops add alpha acid to the wort. Grain mashes are usually at a pH of about 5 but I don’t know whether it stays this high after boiling.
    And ISTR there is a step when recovering yeast for re-use where you disinfect it by washing in acid to kill unwanted bacteria that may be along for the ride.

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