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effect of temperature on the survival of yeast cells

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Postby funky pisces » Thu Apr 26, 2007 5:20 pm

HEY....
DOES ANY1 KNOW WHIVH SECTION WE SHOULD INCLUDE OUR LIST OF VARIABLES THAT WE ARE CONTROLLNG? LIKE SHOULD WE PUT IT IN DA METHOD OR DA PREDICTION OR HAV A SEPERATE SECTION?

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Postby SKG » Thu Apr 26, 2007 5:23 pm

thanx crimson falconperson :) also, a lot of people ahve been talking about using microscopes and when i did my preliminary thing, we were provided with microscopes and slides, so will we lose marks if we don't mention using them, coz i can't see anything about using them on the plan sheet?
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Postby SKG » Thu Apr 26, 2007 5:26 pm

funky pisces wrote:HEY....
DOES ANY1 KNOW WHIVH SECTION WE SHOULD INCLUDE OUR LIST OF VARIABLES THAT WE ARE CONTROLLNG? LIKE SHOULD WE PUT IT IN DA METHOD OR DA PREDICTION OR HAV A SEPERATE SECTION?

FKNX
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i put mine as da first step of da method....i rote about how 2 set up control test tubes, but i u cud include it in an evaluation kinda fing, sayin wot u wud do 2 make it a fair test.
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Postby CrimsonFalcon » Thu Apr 26, 2007 5:27 pm

funky pisces wrote:HEY....
DOES ANY1 KNOW WHIVH SECTION WE SHOULD INCLUDE OUR LIST OF VARIABLES THAT WE ARE CONTROLLNG? LIKE SHOULD WE PUT IT IN DA METHOD OR DA PREDICTION OR HAV A SEPERATE SECTION?


put it into a separate section of its own i should think. after your aim and hypothesis.
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Postby CrimsonFalcon » Thu Apr 26, 2007 5:29 pm

SKG wrote:thanx crimson falconperson :) also, a lot of people ahve been talking about using microscopes and when i did my preliminary thing, we were provided with microscopes and slides, so will we lose marks if we don't mention using them, coz i can't see anything about using them on the plan sheet?


i really dont think you need microscopes.. thats why me have the mehtylene blue - to indicate if they are dead or allive see? this is just an extra appliance to use. and you surely wont loose marks. its jsut one way of doing it, and nobody i know knows of this soo.. i cant see if causing any problems.
best to be using a colorimeter really i rekon. well, thats what im gunna do anyway in my plan ^.=.^

i quote from somewhere here:

A colorimeter has got to be the best idea, measure the intensity of the light getting through the blue colour. Find the maximum light intensity (it will be when all the yeast is dead) and the temperature at that point is your answer.
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Postby Steen » Thu Apr 26, 2007 6:01 pm

I've done it as a separate section but just before the method as it affects the method. But it's an element of choice really
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Postby suzi1234 » Thu Apr 26, 2007 6:20 pm

Doive wrote:you get cold yeast suspension....add a few drops of the methylene blue.....mix it together, it's now blue. You put this mixture into a water bath at whatever temperature you want it at for about 10mins. You then take out the yeast suspension. Then you add the sugar solution to the yeast and see if the blue colour changes. If the blue colour disappears or starts to disappear, there are still yeast cells that haven't been denatured. Is this clear?? If the blue stays as it is, the enzymes are not functioning, which means they have been denatured by the heat.

There seems to be lots of confusion surrounding the methylene blue. It is an indicator, you only add a few drops of it. You mix it into the yeast, you don't add them together and then leave them for 5 mins, you mix them. Add it before you heat the yeast, otherwise it will cool the yeast down.

DOES EVERYONE UNDERSTAND?!!!


Would you add the indicator before or after the experiment because surely if the fermentation hasnt started yet the indicator will turn blue straight away as it detcects the CO2? Would it be better to add the indicator after the experiment and see the color change then??
Im not sure though!!
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Postby CrimsonFalcon » Thu Apr 26, 2007 6:36 pm

suzi1234 wrote:
Doive wrote:you get cold yeast suspension....add a few drops of the methylene blue.....mix it together, it's now blue. You put this mixture into a water bath at whatever temperature you want it at for about 10mins. You then take out the yeast suspension. Then you add the sugar solution to the yeast and see if the blue colour changes. If the blue colour disappears or starts to disappear, there are still yeast cells that haven't been denatured. Is this clear?? If the blue stays as it is, the enzymes are not functioning, which means they have been denatured by the heat.

There seems to be lots of confusion surrounding the methylene blue. It is an indicator, you only add a few drops of it. You mix it into the yeast, you don't add them together and then leave them for 5 mins, you mix them. Add it before you heat the yeast, otherwise it will cool the yeast down.

DOES EVERYONE UNDERSTAND?!!!


Would you add the indicator before or after the experiment because surely if the fermentation hasnt started yet the indicator will turn blue straight away as it detcects the CO2? Would it be better to add the indicator after the experiment and see the color change then??
Im not sure though!!



i really dont think it matters what order you put it in.
as quoted from the paper;
'without seriously affecting' the cells.
so i rekon, if you put it in first, it CAN affect the cells but it doesnt matter, add it after and you need to be careful of the cooling affect but as someone has already said, if they are dead it wont make any differnce. so.... either will do, but if it helps, ive done it so i put it in first with the yeast, heat it up then add sucrose, while keeping it heated in the thermostat. then use the colorimeter etc.
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point to consider?

Postby CrimsonFalcon » Thu Apr 26, 2007 6:48 pm

hey guys... this may be a point some have not considered...

you know that yeast works anerobically to produce the alcohol in fermaentation. well for that to happen it needs to have its O2 supply cut off, so maybe we needed to use a bung on teh test tubes to make the test actually work? add in all the sugar and meth in one go, heat it slowly and see what happens? i though of this eariler today and it kinda made sense, but im not so sure at the mo, but perhaps this is a point to consider?
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Postby Steen » Thu Apr 26, 2007 7:07 pm

You're testing to see if the yeast is alive and so it doesnt matter whether its anaerobic or aerobic but interesting theory - had to think about it for a while!!
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Postby CrimsonFalcon » Thu Apr 26, 2007 7:12 pm

thought so.. i guess thats just another way of carrying out the test. maybe you could get differnt results with this style? becuase you are usign a different respiration? meh. dont matter im not even gunna try changing what i have written to suit this theory. its in tomoz :/
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OH HEY!

Postby CrimsonFalcon » Thu Apr 26, 2007 7:15 pm

oh oh oohh! lok what i FOUND!

Proofing - the testing of the yeast to make sure it is still active. This is done by dissolving the yeast in a warm liquid to which sugar or flour have been added. This mixture is then set aside for 5-10 minutes and should become foamy and bubbly.

Yeast is temperature sensitive:

- at less than 50 F (10 C) the yeast is inactive.

- at 60 F - 70 F (15 C - 21 C) the yeast action is slow.

- at 90 F - 100 F (32 C - 38 C) the yeast is at its optimum temperature for fermentation.

- at greater than 104 F (40 C) the yeast action starts to slow.

- at 138 F (58 C) the yeast is killed


mwhahah! hope that helps people!! off this site!!

http://www.joyofbaking.com/Yeast.html

^_~V *grins*
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