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  • Yeast tastes good. And no, I'm not talking about all the wonderful foods that yeast ferment

  • for us, like bread and beer. I mean the yeasties themselves. They taste good. Boil a packet

  • of dry yeast in a little bit of water to kill the yeast, maybe put in a little pinch of

  • salt, and taste the resulting broth. You know what that tastes like? It tastes like mushroom

  • stock, which I suppose should not have surprised me as much as it did, considering that mushrooms

  • and yeast are the same basic thing.

  • They're both edible funguses, and so they taste a lot alike. They both taste meaty.

  • As we have discussed in previous videos, the fungal kingdom is arguably a lot closer to

  • the animal kingdom than it is to the plant kingdom. And fungi have a lot of the same

  • kinds of things in their bodies as we animals do, such as the amino acids that taste umami-y.

  • We need to eat protein to live, and protein sources that are good for us are likely to

  • contain glutamic acids and some related organic compounds. And therefore we are evolved to

  • find those compounds very, very tasty. That's umami. That's the savory, meaty sensation

  • we get on our tongue. And yeast have a lot of it.

  • Again, maybe you already knew this, but I was completely floored by the taste of a boiled

  • packet of bread yeast. That is good soup. And now I understand why so many processed

  • foods have yeast extract on the ingredients. Check out the ingredients on nearly any dried

  • soup productCup Noodles, or this one, this Lipton noodle soup. Look on the back

  • and you will see yeast listed on the ingredients. Or more specifically, a yeast extract that

  • has been juiced out of the yeast. That's it right thereyeast extract that I juiced

  • out myself. I'll show you how I did that in just a minute. Boil that yeast juice down

  • and mix it with some reduced vegetable broth, and you'd basically have Marmite, this gooey

  • brown stuff the Brits like to spread on toast. The Aussies have a similar condiment they

  • love called Vegemite.

  • And if you taste this stuff, it tastes a lot like that reduced yeast extract, because that

  • is in there. It also tastes like celery and some of the other vegetables that they put

  • in herebasically concentrated vegetable stock is in here as well. There's also a third

  • distinct and very strong taste in here, and that is the taste of beer. Indeed, the story

  • of yeast extract begins with beer. When you brew beer, there is a ton of leftover yeast

  • way more yeast than you would ever need to brew your next batch. And probably even

  • more than the bakery down the street would need to rise their bread. Historically, spent

  • brewer's yeast was regarded as a waste product.

  • Then came Marmite, a company founded in 1902 in the English beer-brewing Mecca of Burton-on-Trent.

  • According to the company's own history of themselves, the founders based their concept

  • on research done by the German food scientist Justus von Liebig. Liebig is also the guy

  • whose work led to the dubious chef wisdom that searing meat seals in the juices, which

  • it doesn't. In his own lifetime, Liebig was much more famous for inventing a liquid meat

  • extract that he said could replace a solid food diet, which it couldn't. But it did taste

  • really good. And Liebig's product eventually became the English stock cube maker, OXO.

  • Liebig also did work on yeast and sometime in the 19th century, he is purported to have

  • done basically what I did here in my kitchen.

  • I took a whole jar of active dry bread yeast from the grocery store and I dumped that into

  • water. Liebig used some spent yeast from a brewer, which probably would've come to him

  • already suspended in some amount of water. In his experiments, Liebig heated this solution

  • to a balmy temperature that activated enzymes within the yeast cells. I don't know what

  • exact temperature he used, but in 2007 these Turkish researchers determined that the optimal

  • temperature for making yeast extract is 50ºC, 122ºF. So that's what I used. Unfortunately

  • for me though, 50ºC is kind of just below the minimum temperature that you can reliably

  • hold in a domestic oven or on a gas stovetop. You're probably going to get a temperature

  • a little higher than that. And at that point, you risk denaturing the enzymes in the yeast

  • that we need for this process. Soelectric heating pad.

  • It took me a while to find the right setting and the right way to wrap this around the

  • bowl to get my target temperature. And even when I did, the temperature suddenly shot

  • up when my dried yeast woke up and they started metabolizing the energy stores in their little

  • unicellular bodies. That is their body heat, thermogenesis. I had to rip the heating pad

  • off so that my solution did not overheat, but then the yeast calmed down after a while,

  • because I didn't give them any food to eat in that water. So they just kind of stopped

  • metabolizing, my temperature plummeted. So I had to put the heating pad back on. And

  • when I did that, I was not able to get the temperature up high enough. This just wasn't

  • hot enough. I was only able to hold my bowl at like 35ºC for a day. And basically nothing

  • happened. This is not yeast extract. It's just warm yeast in warm water. It tastes okay,

  • but not super strong.

  • And you generally don't want to eat very, very much live yeast. Speaking of microorganisms

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  • off at tryombre.com/adam. That's in the description. Thank you Ombre Lab.

  • But anyway, yeah, I could not get enough heat to squeeze the juice out of my yeast. So I

  • went out and I bought a much bigger heating pad. I tied it snug around the bowl with a

  • cute little scarf and there, a perfect 50ºC. I held it there for 24 hours, which the aforementioned

  • Turkish researchers found as the optimal time to achieve what Justus von Liebig achieved

  • before me, and that is yeast autolysis. It's funnywe just talked about autolysis last

  • week when we were talking about gluten proteins in flour. Autolysis basically means cellular

  • self-destruction. At this temperature in water, enzymes within the yeast cells break down

  • their own cell walls, causing their little yeasty guts to spill out into the solution

  • and further reactions break down their proteins into more of the tasty umami-y amino acids

  • and such that we like to eat.

  • That semi-clear liquid is the lysatethe extracted cellular guts dissolved in water.

  • I should have just siphoned it off the top because my filter here did not do such a great

  • job of removing the solids that had settled on the bottom. Those solids are what's left

  • of the yeast cell walls. That's what's in the slurry there: cell wall debris. It's often

  • filtered out with a centrifuge at yeast extract factories. I suppose it dilutes the flavor

  • of the extract, but I will say it actually makes kind of a nice thickener. Here's some

  • homemade yeast extract that I did not filter at all. I boiled it down. I put in some onion

  • powder and some celery seeds to mimic the vegetable flavors they add to Marmite. And

  • that's honestly some good vegan gravy right there. The cell wall debris gives it a really

  • creamy texture.

  • I will say that creamy texture could be due in part to an additive that they put in grocery

  • store bread yeast like this. It's called sorbitan monostearate. It's an emulsifier. They put

  • it in there to keep the yeast from getting too dry when they're in storage. And also

  • it helps the yeast to rehydrate inside the dough. Seems possible to me that this additive

  • is forming a water-and-oil emulsion here in this solution with the lipids naturally present

  • in the yeast. And that might be contributing to that creamy texture. And it also might

  • be making my extract harder to filter. I basically have yeasty mayonnaise gumming up the works.

  • But for what it's worth, I also did a test with an organic yeast packet that does not

  • have any emulsifier inside it. And when I boiled that down to a paste, it still had

  • a somewhat creamy texture. So, who knows?

  • All I know is, according to the story, Justus von Liebig filtered the solids out of his

  • lysate, he boiled it down to a glaze and he was struck by how closely the taste of that

  • resembled a reduced animal stock. That's basically vegan demi-glacé. Quite tasty. So based on

  • Liebig's experiments, these folks built a factory in Burton-on-Trent, and they tried

  • to work out a process for converting cheap, ubiquitous spent brewers yeast into a food

  • fit for human consumption. One problem they ran into is that brewers yeast is covered

  • in bitter residues from the hops. You have to de-bitter the yeast. And even after they

  • do, Marmite is still a little bitter. I'm told most people who eat this on toast do

  • a very thin layer, and then they cut it with some butter. I do think that's quite tasty,

  • but it does still very much taste like beer.

  • Whereas the extract that I made from bread yeast does not. Nor does this so-called nutritional

  • yeast taste like beer. Not at all. This company says they grow their own yeast in a molasses

  • solution rather than getting it from brewers, so there's no hops residue, there's no grain

  • residues. But it's not a yeast extract. It's whole yeast, baked until they die and they

  • form little flakes that you can use as a seasoning. It's quite tasty, but not nearly as strong

  • as the extractbecause of all of the cell wall debris that's still in there, I assume.

  • I had hoped to be able to give you a practical recipe for homemade yeast extract. There are

  • a lot of ones on the internet and they all have big problems in my opinion, and I did

  • not do any better. One problem is that this bottle of yeast is $6 and you want to see

  • how much extract I was able to get out of it? This much. That's what I got. Not very

  • cost-effective. I also do worry about the sorbitan monostearate content in here, the

  • emulsifier. Every food safety agency on earth considers that stuff perfectly safe in the

  • amounts that you would eat if you were using a little dry yeast to bake a whole loaf of

  • bread. I have no idea how much of it you would end up eating in a concentrated yeast extract.

  • And I have no idea if that amount would be safe. No idea.

  • I figured I could remedy both of these problems by simply growing my own yeast at home from

  • one little starter packet. I put one little packet into about a gallon of sugar water,

  • and I watched it bubble for a few days before I realized that I'm basically making rum here.

  • This is now a terrible-tasting alcoholic beverage that you could distill into rum. The thing

  • about making alcoholic beverages, it's actually kind of tricky to do well. You could get all

  • kinds of contaminants in here. This had a pretty funky smell. And the bread yeast seemed

  • to shut down long before they'd fermented all of the expensive sugar I gave them. There's

  • not that many yeasties in there, and I was totally unable to filter them out of my stanky

  • bathtub hooch. Maybe you can figure out a good way to grow yeast at home for extract.

  • Or maybe you could get it from a friend who home-brews. The problem is then you would

  • have to de-bitter it. And apparently, the processes that they use for de-bittering yeast

  • at the factory are pretty industrial, pretty intense, not easy to replicate at home.

  • So maybe just buy yeast extract instead. Here in the States, I get Marmite at the grocery

  • store, Publix, which has a British import section, #NotAnAd. This is the same import

  • section that has these OXO cubes that are nearly solid yeast extract. There's no animal

  • product at all in these. People originally considered yeast extract to be an adulterant

  • in stock cubes — a cheap imitation of real meat. But I think this stuff is great in its

  • own right and I'm not even a vegan. If you are a vegan, definitely check out yeast extract.

  • It's rich in the B vitamins that can be tough to get if you don't eat any animal products.

  • Indeed, researchers like this American chemist in 1916 came to understand the necessity of

  • B vitamins in part through their experiments with yeast. They fed pigeons a diet of only

  • plain white rice and the birds got really weak and wobbly. Same thing happens to humans.

  • We call the resulting disease beriberi. The researchers gave those pigeons white rice

  • fortified with yeast extract and the pigeons got better, because B vitamins. Yeastone

  • of humanity's best friends.

Yeast tastes good. And no, I'm not talking about all the wonderful foods that yeast ferment

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Why yeast extract is in tons of foods (and why it's delicious)

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    Emily に公開 2024 年 05 月 03 日
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