How to best deactivate yeast?
I've been using an overfermented sponge for dead yeast. While making some French like loaves, I noted a flavor I did not care for. I tried the same technique, but instead of using flour, using malt extract in water and brewed much like beer, using instant yeast instead of a strain of brewers yeast. This has been interesting, with some mixed results so far, one batch of which had a lot of dead yeast, and it worked very well. However, like homebrewing, it involved a lot of sanitation steps, boiling of the wort, etc, and was from a labor standpoint, more work than the less good tasting flour-based overfermented sponge.
All I'm interested in is dead yeast to help relax dough. So far as I know, dead yeast is known as "deactivated yeast" in baker's terms. This is a product that is available to pizza shops, but so far as I know, is not available to consumers at retail level. A search this morning led to suggestion of nutritional yeast. Does nutritional yeast flavor the baked bread in the same way as pizza shops "deactivated yeast"? An SFBI pdf mentions deactivated yeast, but only to get it from a manufacturer.
Alternatively, is there some fast and easy way to deactivate baker's yeast?
An idea that occurred to me just this morning would be to use any form of dry baker's yeast, I'd use instant yeast. Dissolve it first in 4 times its weight of water for 10 minutes or so, then microwave it, or mix it with additional boiling water, the objective being to bring it above the temperature that would kill the yeast to break its cell walls. Has anyone tried this?
This could also be practiced on a batch of malt extract grown bread yeast to insure the yeast that was killed was the freshest available.
I have no idea of what you just said! Are you brewing bread or baking brew? You taking flour, water, salt and yeast to a level way over my head. Good luck with your project and please include photos.
a baker's product that is not, or doesn't seem available at retail level.
My old ship was deactivated and eventually scrapped- that is the only type of deactivation I am familiar with. Good luck.
to deactivate. I guess just heat it to 140°F for a minute or two.
We all eventually get scrapped!
deactivated yeast is rather considered a health food.
Have a look at this link; it explains quite well: http://en.wikipedia.org/wiki/Nutritional_yeast
The process is involved and not really meant for amateurs (no offence intended).
It may have added B12. It may work for the purpose, but if it has added vitamins, I'd presume it would skew the flavor somewhat, so perhaps not desirable as a solution. I've purchased that in bulk in the past, I don't recall it ever coming with an ingredient list saying whether or not it did have added vitamins.
Here's one deactivated yeast product meant for bakers, for the purpose I described.
http://www.lsaf.com/products/reducing-agent/saf-pro%C2%AE-relax%C2%AE-rs-190
It doesn't seem available in small quantities, thus the desire to make it from regular baking yeast. They have two products, one that imparts flavor, and one that says it doesn't or that flavoring is minimal.
This was one of my first experiments, I didn't use an airlock, it fermented only overnight. One surprising thing I found is that the yeast growth seemed to terminate, and it would not rise dough afterward. Had I been brewing beer (for drinking purposes), I would have used a different yeast which is rather pricey compared to instant dry baker's yeast.
What is pictured is barley malt syrup (probably was 10% of water weight, and it was not the lightest colored extract) mixed with water, and boiled for a short time, then cooled and pitched with some baker's yeast, using some brewers sanitation processes. After the boil, mixing air in is important, I used a sanitized whip. There were no hops added as would be common with beer. That was added to some batards I made, and the dough ended up too relaxed, but the crumb had nice big holes, and the malt extract colored the bread a bit. I had to add more IDY to get the dough to rise.
Alcohol apparently dissolves gliadin, at least that's what I've read, and there would not be any alcohol in a dry deactivated yeast product.
Lesaffre Yeast Corporation
(414) 615-4094
I should call them and talk to them. Maybe I can find time today.
request a sample...they will usually do so gladly.
instant yeast into a small hot dry frying pan until it starts to smoke a little bit or toast a tiny bit, just a few minutes. Then it's dead. It is actually quite tasty and is deactivated. I quickly poured the toasted yeast into a coffee cup and stuck in the probe thermometer to make sure it was over 50°C. I later mixed half teaspoon dead yeast with water and all it did was separate and sit on the bottom of my shot glass. Proof it was dead. That's when I noticed the nice aroma.
I mixed some into my snow bread dough as a control and it did impart a nice flavour. Because of the "dough conditioning" I used toasted yeast because I didn't want any gas from the yeast but did want other side effects.
Mini-o-killer-of-yeasties :)
Can also dissolve yeast into water and bring almost up to a boil as you mentioned. But toasting tastes better.
It might be that the flavour you stumbled upon and didn't like is a vinegar. Try adding other types of vinegar that you can identify and appeal to you instead of reinventing the
wheelprocess. Too much trial and error even for me. Head for the cider vinegars and pear vinegars for your French sticks. What country are you located?I don't think the less than optimal flavor was vinegar, I used to add white vinegar to some of my white bread recipes, and this didn't taste like that. It wasn't bad, it just wasn't awesomely great.
My understanding of what happens with deactivated yeast is that when the yeast cell dies, it releases some to much of the fluid that was inside the cell. I'm not sure what its "innards" contains, but I've read it may include various proteases, while glutathione is frequently mentioned, I'm not convinced that's all that's at play. In the case of glutathione, it is also reported as a component of raw wheat germ, as well milk. In both of those cases, heat is used frequently by bakers to destroy it so that the bubble structure of a crumb will form. Glutathione is reported as one reason why flours that contain raw wheat germ and made into dough generally will not rise as high as as white flour doughs, so toasting the germ is one method of managing that to destroy the glutathione. In the case of milk, it is frequently scalded, at least in the old days it was. So, my point is that if it is glutathione which is primarily responsible for the increase in extensibility that is caused by dead or deactivated yeast, something which I'm not at all certain about, then heat deactivation of glutathione would seem to be undesired.
In brewing beer from grains, the "mash" it is called, temperature sensitive soaks of the grain are made at various temperatures ranging from 113°F (or lower) to 170°F, while 150°F is a common one-step mash temperature. When temperatures are increased beyond that, enzymes are destroyed. Anyone who makes oatmeal for breakfast can see this in action, if they boil water first and then add rolled oatmeal to the already boiling water, the grains will swell and soften but they will stay more intact. If instead they put the oatmeal in the pan with cold water, and then heat it to boiling, the oatmeal will be creamier.
Going back to the dead or deactivated yeast, while it is said that glutathione is the primary component responsible for the increased extensibility, there are a number of enzymes that are active in yeast, and when yeast dies, its cytoplasm leaks out of the cell. Many of these active elements are destroyed by too much heat. So, low temperature killing of the yeast may be preferred. That leads to the question of just what temperatures are optimal for deactivation of the yeast.
So far in my experiments, I have not used heat, rather the known yeast curve of lag, exponential, stationary phases, followed by a death phase, and it is this latter portion which is of interest. In sponges it seems to occur coincident with or after "the fall". This is the same curve anyone who makes a sponge or poolish eventually learns. The problem with this is that it is difficult to know how much dead yeast exists among the yeast still alive, there are a number of process factors that can vary this including time, sugar concentration, dissolved gases, temperature, and presumably other factors, and so measurement and consistency of results is a rather complicated issue, and I'm believing not an insignificant one due to inconsistent results I've experienced. Sometimes I have very extensible dough, other times it doesn't seem extensible at all. Thus the idea that one can measure a certain amount of dry yeast, bring it quickly back to life via hydration during the lag phase, then kill it while keeping any enzymes active, is appealing to me for consistent measurement reasons. I don't know if hydration is necessary or not, but it seems like a good idea if what is desired is to get what was inside the cell wall, outside of it.
As you say, reinventing the wheel is like spinning the wheel too many times.
BTW, I'm in Southern California.
I often tuck a ball of low hydration rye sourdough into my fridge for long term storage. Last summer I opened a jar almost 2 yrs old that smelled of yeast extract and a very dark brown colour with no growths or moulds. I attempted to get an active starter going from it but not sure it "took." The flavours were off in the starter. I used another starter sample to jump start a starter.
I parked what was left of the dark sourdough ball back into the fridge, the yeast being most likely very dead but thought it might be worth something or experiments when I found time. Well at the beginning of Jan, a few weeks ago, I crushed what was left with water and let it settle out. The top water was clear dark brown and aromas were not unlike soya sauce. I poured off the coffee coloured liquid and added water to feed various house plants. The rest, slurry of dead yeast cell walls, bacteria and spent flour went into the compost.
So it's gone but you've got me thinking about it again. You might want to look into soya sauce, it's made from fermenting soya beens and grains.
Cell walls will crush between glass, did it enough times trying to observe them. I think you could run your yeast cells in a blender to break them open. Freezing plump yeasts also tends to break them.
It's just occurred to me that if you add enough alcohol to a yeast mixture it should kill the yeast without using heat, and when it's dried the alcohol will evaporate.
There's a possibility that the alcohol may cause chemical changes in the yeast, although probably not to the same extent as heat.