proofing yeast

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I need to add yeast to cut bananas to make food
for my Drosophila fruit flies.  Currently, what
I do is combine 1/2 teaspoon calcium propionate,
3 teaspoons cream of tartar, 2 tablespoons water,
and 1 teaspoon yeast in a jar, give it a good
shaking, and set it aside while cutting up the
bananas.  After the bananas are cut up into tiny
cubes, I give the jar another good shaking, then
pour over the bananas and mix by hand for about
30 seconds.  During this mixing, it seems like
a lot of liquid comes out of the bananas.  Then,
I spoon it into the cups where the flies will
live.

Until recently, I used a whole package of yeast,
which is about 2 teaspoons.  I've been battling
problems with bacterial overgrowth, and cutting
the yeast back to about half has helped a lot.
I tried lower amounts, but that seemed to hurt
the production of flies.

Giving the jar two good shakings seems to have
helped.  My theory is that the first shaking
mixes the ingrediants and wets the granules of
active dry yeast.  The time delay while I cut up
the bananas allows the water to soak into the
granules.  Then, the second shaking breaks up
the now softened granules and distributes the
yeast more thoroughly.

There does seem to be some yeast activity which
starts in the jar, even though I've added no
sugar or starch.  The first food the yeast get
should be the liquid from the bananas.

I'm still not satisfied with my results.  If
I use the whole package of yeast, I lose more
cups to bacterial overgrowth, but the best cups
produce more flies.  If I use half the amount,
it seems like the best cups produce less, but
I get fewer bad cups.

I'm thinking that maybe I'm not handling the
yeast right before adding it to the bananas.
Maybe I should add sugar or flour to the yeast
at the jar stage, so they'd get started eating
earlier.  The cream of tartar is a buffered acid
which helps to suppress bacterial overgrowth.
Calcium propionate is a mold inhibitor which
also helps to suppress bacteria.  The water is
always room temperature bottled water, not tap
water.

Any of you yeast-proofing experts out there have
any suggestions?

Re: proofing yeast
On Sun, 22 Sep 2013 15:00:49 -0800, Mark Thorson wrote:

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Call me bananas for asking the obvious, but why are growing fruit
flies?

-sw

Re: proofing yeast
On 9/22/2013 9:21 PM, Sqwertz wrote:
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I'm glad I'm not the only person who wondered about why he's feeding  
fruit flies.  Next thing you know he'll start a flea circus. :)

Jill

Re: proofing yeast
wrote:

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Research labs grow fruit flies for medical experiments, etc. because
the fruit fly's entire life cycle is only 24 hours.

Re: proofing yeast

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It's much longer than that, even in the wild. I did a fruit fly genetics  
experiment in high school. They're pretty precocious critters. They're  
ready to mate within 8 hours of coming out of the pupae.

Cindy

--  
C.J. Fuller

Delete the obvious to email me

Re: proofing yeast


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I wondered that too??
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Re: proofing yeast
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I'll hazard a guess that it's to feed some sort of reptile pet.  



Re: proofing yeast
Sqwertz wrote:
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I'm growing a mutant strain that makes sepiapterin.
Sepiapterin is a precursor for tetrahydrobiopterin,
which is an essential cofactor for the enzymes that
perform the rate-limiting step in the synthesis of
most of the major neurotransmitters in the brain
(dopamine, epinephrine, norepinephrine, serotonin,
melatonin, and nitric oxide).

Re: proofing yeast
On Mon, 23 Sep 2013 19:59:41 -0800, Mark Thorson wrote:

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Uh <ahem>.  You're trying to do all that, yet you're asking *us* how
to grow a simple single-celled yeast?

Call me skeptical.

Supposing you get that far, how do you capture the sepiapterin?  Do
you get the flies to pee into little tiny cups?

=sw

Re: proofing yeast
On 9/22/2013 9:21 PM, Sqwertz wrote:
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I wondered too unless the fruit flies produce something exotic.

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