The limits of a certain amount of yeast

[Bvbellomo]

I know if a packet of dry yeast is enough, we can pitch it directly. But if it isn't enough, we make a starter. And sometimes if a home brewer drinks an interesting beer, they add wort to the bottle and successfully use it in a 5 gallon batch. It seems like only a few viable cells of yeast could make unlimited beer with the right preparation.

But I also know extreme underpitching doesn't work. I've never made 50 gallons of wort, but I know if I did I couldn't just throw in a single dry yeast packet. But could I make a 1 gallon starter from a single packet, add it to a 5 gallon batch and using that itself as a starter for 50 gallons of wort? Would that work? If so, how is it different from just throwing 1 packet in 50 gallons (or 500 gallons or 5000 gallons)?

How do commercial brewers do it? I can't imagine they are standing above a huge fermenter and opening hundreds of 11 gram packets of Fermentis.

 

[Soulshine2]

They don't . They have many ginormous vats fermenting at any given time, and so have the same "unlimited supply" of active yeast cake going, like a sourdough . I'm sure someone will come in and say different but I'll venture a guess this is how they did it in the old days. Nobody even included yeast to their ingredient lists because they didn't know it existed when in fact it did but it was more than likely a wild yeast that got into the wort and after one tasted it , they kept it going.
In theory , I believe you could indeed work up a batch of yeast to start any given size batch of wort.

 

[mongoose33]

Commercial breweries that buy yeast buy it in large packages. They aren't opening dozens of little packets of yeast. White Labs, for instance, produces only commercial quantities of yeast in their Asheville labs; the smaller packaging we homebrewers use come from San Diego.

You can, in theory (and in practice--people have done it), capture yeast from a bottle and build up the population enough to then pitch it, but you'd have to be pretty motivated to do that. You'd also want to get the pitching numbers in the right area, and to do and know that, you'd need to do cell counts. For that, a microscope, a hemocytometer, a few other items.

 

[kh54s10]

First of all dry yeast is engineered so that you don't need a starter, in fact doing a starter with dry yeast is detrimental to the yeast. Second, the yeast companies sell yeast in large packages to commercial breweries.

You can, in theory (and in practice--people have done it), capture yeast from a bottle and build up the population enough to then pitch it, but you'd have to be pretty motivated to do that. You'd also want to get the pitching numbers in the right area, and to do and know that, you'd need to do cell counts. For that, a microscope, a hemocytometer, a few other items.

I have done this successfully. I collected the last 1/2 inch of each bottle in a 6 pack, ran that in 250 ml of 1.025 wort. After a day I added .5 liter of 1.030 wort. After another day I cold crashed that and had what looked like a vial of liquid yeast so I did a calculated step at 1.040. Cold crashed and examined. That looked like what I usually pitch after making a single step starter.

I guessed that Long Trail Brewery might be using a house yeast, or at least I didn't know what yeast. I used it in my Long Trail Pale Ale clone and it was significantly closer to what I remembered the ale to be like. I can't test since they don't make that one any more.

I just did it by eye. I did not use a microscope, hemocytometer, or any other special item. It was very successful and not too difficult.

I also freeze yeast and it takes similar stepped up starters so that was not so unusual to me.

 

[passedpawn]

I know if a packet of dry yeast is enough, we can pitch it directly. But if it isn't enough, we make a starter. And sometimes if a home brewer drinks an interesting beer, they add wort to the bottle and successfully use it in a 5 gallon batch. It seems like only a few viable cells of yeast could make unlimited beer with the right preparation.

But I also know extreme underpitching doesn't work. I've never made 50 gallons of wort, but I know if I did I couldn't just throw in a single dry yeast packet. But could I make a 1 gallon starter from a single packet, add it to a 5 gallon batch and using that itself as a starter for 50 gallons of wort? Would that work? If so, how is it different from just throwing 1 packet in 50 gallons (or 500 gallons or 5000 gallons)?

How do commercial brewers do it? I can't imagine they are standing above a huge fermenter and opening hundreds of 11 gram packets of Fermentis.

Like Mongoose said, although you can underpitch and expect full fermentation, it will be delayed. During that time, you've got a bunch of sugar water sitting there and airborne bacteria will have its way with your beer. Bacterial growth is much, much quicker than fungal growth (yeast). So you want to make sure to pitch enough yeast to ensure a quick start for your beer. Once alcohol is produced, bacterial growth is inhibited. Now, you might wonder why a starter doesn't get infected then. They don't because you start with a relatively large ratio of yeast cells to wort, and the beer ferments quickly, creating alcohol which then inhibits bacterial growth. Of course, the safest solution is to just pitch lots of new yeast and to skip the starter altogether.

Commercial brewers use large quantities of yeast. You can buy dry yeast in 500g packages (the little packets contain 11g). For example, here: https://www.homebrewing.org/500-g-F...12.html?utm_source=google&utm_medium=shopping

I've been to breweries where they do indeed skim yeast from one batch to use on the next. The yeast was contained in large steel buckets and was a thick milky slurry, just as you'd expect. I posted a video of that below.

If you attempt to reuse yeast repeatedly over many generations, the cells might mutate. And unless you're doing some kind of acid washing, you might also have increasingly large growths of unwanted bacteria and unwanted fungi. In fact, I brought yeast back from that german brewery where I took that video and observed a surprising amount of bacteria in there (I've got a microscope).