Naked Science Forum
General Science => General Science => Topic started by: Karen W. on 15/10/2007 20:24:50
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Well I am curious as I have always been taught that when baking my sourdough?
I am splitting a topic and adding here to further explore this Question.
Hummmm I really don't know.. but something set me to thinking, and why can I not use a metal bowl.. I know yeast things loose their rising ability cause and I believe the metal kills the yeast.. what reaction happens when it is made in a metal bowl?
The bread thing is an old rule of thumb with yeast. It is OK to cook with it but the yeast if you notice your bread machine instructions will tell you to make a well in the flour and put your yeast in the well of the flour .. this avoids direct contact before yeast has been mixed and activated. I think it has to be activated first.. Mine has the metal pan also!
Quote from: sophiecentaur on 16/10/2007 22:32:27
your bread machine instructions will tell you to make a well in the flour and put your yeast in the well of the flour .
I thought that was just so that you could set a delayed start time and avoid the yeast getting wet before it was needed.
My Grandma said, metal objects killed the yeasts ability to create the rising action needed for your breads! I have noticed it to be true. If you mix the yeast directly in the metal bowl then it just does not work well!
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My guess is that most of the Western world's bread is made in metal "bowls".
However there are lots of oxidation reactions that are catalysed by traces of metals and these might spoil the scent.
There's nothing in particular holding the scented oil in the flowers to begin with so the oil just gives the essential oils somewhere to go by diffusion.
BTW, do you realise that the last bunch of lavendar you use is soaked in scented oil so it still has a lot of scent in it.
If you were to do this commercially you would do better to keep reusing the flowers. If you used that last bunch to scent the next batch of oil you would get more scent from the flowers but it would be more time consuming.
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your bread machine instructions will tell you to make a well in the flour and put your yeast in the well of the flour .
I thought that was just so that you could set a delayed start time and avoid the yeast getting wet before it was needed.
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Sudden changes in temperature probably upset yeasts.
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Looking on the Web, everyone seems to agree that metal harms the yeast so I have to go along with it. I must say that I have had occasions when the bread hasn't risen right. I never determined why. I must try to vary the method and observe what happens.
The breadmaker tub has to be metallic in order to stand the heat of cooking, so I suppose it is a compromise.
It would be nice to have some Scientific input as to the reasons for 'metal' spoiling the yeast. Some 'ionic' reasons, I suspect; it always is with Biology.
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That is probably true as too hot will kill it also before it has had a chance to become active. too cold just seems to take longer to activate..
http://www.tyler.net/jpwright/sourdo.htm
Your new sourdough is young and needs special care for the first few days. Taking care of it will be easy once you realize what it is you actually have. You have a flour and water mixture that is providing a home and a food supply for symbiotic colonies of yeast and lactobacilli. To keep your little community healthy, simply feed it and keep it away from excessive heat and metal containers. (The lactobacilli give off acid. This acid protects the bacilli and the yeast from invaders, but it also reacts with metal containers, tarnishing the container and contaminating the sourdough with harmful metal compounds.)
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What I know is that usually metals inhibit enzymes (yeast produces the enzyme Amylase), but I don't know if this is what happens in this case.
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That sounds plausible Alberto, thanks for the information and post in this topic.
Nice to see you!
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That sounds plausible Alberto, thanks for the information and post in this topic.
Nice to see you!
Thank you Karen.
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too hot will kill it
The funny thing is that, with the supermarket, activated yeast, it seems to prove at an amazingly high temperature - almost whilst it's outside is starting to cook. They really are tough little devils.
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Yes do you mean the quick rising yeast packets?
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That sounds plausible Alberto, thanks for the information and post in this topic.
Nice to see you!
Thank you Karen.
Your welcome..
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"Looking on the Web, everyone seems to agree that metal harms the yeast "
Nuts to the internet; it's perfectly plain that if yeast was harmed by metals, the modern beer and wine industry (which does everything in stainless steel vessels) couldn't exist.
Since it does exist the preimise that metals harm yeast must be false. I don't see how it matters how often this falsehood is repeated or on what medium. It doesn't matter if they anounce it on the BBC news- it still won't be true .
"What I know is that usually metals inhibit enzymes (yeast produces the enzyme Amylase), but I don't know if this is what happens in this case."
What I know is that many enzymes need metals to work. A quick search on "copper protein yeast" or the equivalent with zinc shows lots of stuff about metal dependent effects in yeast and its enzymes.
What is true is that large amounts of (at least some) metals can be toxic to the yeasts but, at those levels, the bread probably wouldn't be fit to eat.
(Incidentally, most yeast used in brewing doesn't produce much amylase- that's why grain is left to sprout (malted) before tuning it into beer).
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I agree with BC : the only valid statement would be that SOME metals are harmfull in brewing and baking conditions.
From memory, I can state that calcium (which after all is a metal, too) is actually favourable to the working of yeasts and especially of amylases. In fact, brewing with soft water is no easy task.
Zinc on the other hand is used to stop amylase activity (in other situations than baking or brewing).
I know of one or two cases were repairs to brewing kettles turned out badly because either the sheet metal or the solder used were not up to specifications (or were incorrectly specified in the first place).
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How about copper or aluminium - they are the most likely metals to have been used for mixing bowls in the past?
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How about copper or aluminium - they are the most likely metals to have been used for mixing bowls in the past?
Again from memory : copper and aluminium themselves don't harm yeast activity, but some alloys do - e.g. brass will kill off yeast almost instantaneously. (In one of the cases mentionned above they had used solder that wasmeant for brass for repairing the brewing kettle).
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When I get back from the hospital...I fully expect to you three, have taken photos, and done
a well tested experiment, with different types of metal dishes, verses glass, plastic, or what
have you, and yeast..! Lets see which causes the least activity, or none.. which one fails to
bubble, or become active?
You should each take two different types of containers, and use the same type of yeast..
regular, not fast rising!
Hugs.. Have fun..!! I want to see the results
Gentleman!
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and who is going to eat all that stuff ?
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Since when would we want to confuse a good discussion with actual observed facts?
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LOL Have fun Guys! Bye
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Oh, Karen, "Why does would metal...", you were not referring to what is known as "Wood's metal", would you ? It is a kind of solder, and it is unfit for baking conditions. I don't know about its effect on yeast, but it melts at temperatures like 80°C. It would melt in the oven.
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Oh, Karen, "Why does would metal...", you were not referring to what is known as "Wood's metal", would you ? It is a kind of solder, and it is unfit for baking conditions. I don't know about its effect on yeast, but it melts at temperatures like 80°C. It would melt in the oven.
What do you mean???? Did I say something about wood metal...???
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Well, the initial question read "Why does would metal kill yeast..." so I thaught it might have been a spelling error.
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OH my Goodness!!! LOL LOL I can't believe I missed That! Thanks it is indeed an error.. I will fix it! !!! Thanks Eric! HEE HEE!