Supermarket fly food
Adelaide T C Carpenter
atc12 at mole.bio.cam.ac.uk
Thu Jul 27 09:09:42 EST 2000
Supermarket Fly Food
Advantages relative to standard cornmeal food: very easy to pour by hand
-- dribbles much less; therefore can pour at a much faster rate; usually
can be plugged (= no moisture inside vials) after only two hours; easier
to clean the pots afterwards
Disadvantages relative to standard cornmeal food: gels too stiff for
further pouring at a higher temperature, therefore *have* to pour faster;
this probably means unsuitable for large batches and/or commercial steam
kettles - I haven't tried
As always, adjust levels of agar/corn/wheat products to suit the
stiffening strengths of your own brands; I and my flies prefer a fairly
stiff food, one that the larvae can burrow into and still breathe.
For ca 4 liters (enough for 400+ vials):
40 g Agar. Add to 600 ml water in beaker. (This step is strictly
speaking necessary only when using coarse, cheap agar but it does make the
cooking easier; see "Afterthoughts" for a variant)
300 g glucose
280 g polenta (the dry grain, not the pre-cooked: and unflavored!)
50 g couscous (ditto)
120 g yeast
30 g soy flour
Mix the above dry ingredients together until well blended, breaking up any
lumps; this makes wetting the mixture easy.
Measure out 800 ml of water; add about half all at once to the
dry mixture and stir vigorously to get all of it damp. Add about half the
remaining water and mix until smooth. This mixture will settle out; keep
stirring occasionally until ready to use. Add more water as necessary to
keep this slurry fairly liquid; if you don't need all 800 ml for this,
add the residue to the next step. The mixture should be well wetted at
least 2 minutes before it is added to the cooking solution.
Take a large kettle (ca 8 liter capacity); add 2 liters of water and
bring just to the boil. (Our gas hob heats very quickly; since it is
important to be doing nothing else once the agar is added I start this
heating after getting everything else ready. If your heating capacity is
slow you may prefer to begin heating earlier in the process.) Mix the
agar slurry and add all of it to the boiling water. Stir. Continue to
heat until the agar foams up -- this is very important; you do not have
assurance that all of the agar is dissolved until it foams up! On the
other hand, you do not want boiled-over agar all over your kitchen. Do
not let yourself be distracted at this point!
As soon as the agar has foamed up, give the polenta etc. mixture
one last stir and add it to the pot. This will calm the agar foaming.
Stir everything well together and keep stirring frequently; until it
starts to cook the couscous will attempt to settle out. Rinse out the
Continue to cook until it reaches the fullest, plopping boil. If
you're not sure you've reached this state yet, be patient and keep at it.
Once this full boil is reached, time 30 seconds; then turn the heat off
and stir stir stir until all hints of plopping have ceased, the volume is
minimal and the level of steam being released has decreased. Add 100 ml
of Nipogen solution => !! VERY CAREFULLY !! The alcohol can very easily
boil up. (Or the equivalent amount of your own favorite fungicide.) Stir
it *gently* into the rest of the mixture at first, until the alcohol has
stopped bubbling, then stir vigorously and very thoroughly. Continue to
stir until no hint of alcohol vapor can be smelled.
Pour. I use two 1000 ml handled round plastic beakers with sharp
spouts; one stays in the pot for dipping out the next aliquot, the other
is for pouring. Take no more than 500 ml at a time. Pour as quickly as
As soon as the kettle is empty, run hot water into it while you
finish pouring the last half beaker of food. Pop the beakers etc. into
the kettle of hot water. Cover the food. Sluice down the beakers etc. in
hot running water; all the congealed bits should sluice off freely,
though you may need to encourage non-smooth surfaces a bit with
fingernails. Ditto for the kettle. Get *all* the bits of congealed food
off and wipe dry.
Clean all counter surfaces completely. Your own spills will be
easy since still fresh; older ones are more difficult but simply soaking
them in a little water for about a minute will loosen them enough for
Variant: add the agar to the other dry ingredients before mixing them.
Add the agar water to the "dry" water, i.e. 1400 ml total. As before, add
ca half the total mixing water all at once, mix thoroughly until all
ingredients are at least damp, then add more water until the mixture is a
thin slurry and add yet more as the dry ingredients take it up. Boil the
2 liters of kettle water plus any mixing water left over, add the slurry,
stir well -- and keep stirring continuously and across the bottom of the
vessel until the agar is melted: the surface of the mixture will change
from cloudy to glossy. After that, intermittent stirring is sufficient;
before that stage, lack of stirring will permit the agar to settle to the
bottom, cook hard, and make a real and awful mess (as well as resulting in
food that is too soft). Again, bring the mixture to a full and plopping
boil, time 30 seconds, stir stir etc.
This variant is useful when the cooking pot isn't large enough to
contain the full volume of the foaming agar; apparently the increase in
boiling point from the sugar assures that all the agar gets melted.
However, I personally find the constant stirring needed in this method to
be more of a bother than watching for the agar to boil up in the previous
version, so I boil the agar separately whenever the pot is big enough.
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