From owner-drosophila@net.bio.net Sun May 21 23:00:00 1995 Path: biosci!bloom-beacon.mit.edu!gatech!news.sprintlink.net!demon!doc.news.pipex.net!pipex!sunsite.doc.ic.ac.uk!charlie.lif.icnet.uk!mac030004.ox.icnet.uk!user From: d_horowicz@icrf.icnet.uk (David Ish-Horowicz) Newsgroups: bionet.drosophila Subject: Re: help with food Date: Mon, 22 May 1995 13:05:16 +0000 Organization: ICRF Developmental Biology Unit Lines: 37 Message-ID: References: <00990B43.AE0B4C85@nefeli.imbb.forth.gr> <3ppnjl$3es@lyra.csx.cam.ac.uk> NNTP-Posting-Host: mac030004.ox.icnet.uk In article <3ppnjl$3es@lyra.csx.cam.ac.uk>, flh@mole.bio.cam.ac.uk (Frances Hannan (Zoology)) wrote: > delidakis@nefeli.imbb.forth.gr writes: > > >if you have any modifications on the following recipe, we'd like to try them: > > >Per 3 litres of water we use: > >70 g sugar (sucrose) > >170 g yeast (baker's yeast cake previously autoclaved to make sure it's > > dead) > >30 g agar > >200 g cornflour > >+ 50 ml of 10% Nipagin (0.17% final) > > You could try adding a mixture of propionic and phosphoric acids to the > fly food after it has cooled down a bit (if food is too hot you will > still get some bacteria/slime). Try 0.5% propionic acid and 0.05% phosphoric > acid (final concentrations). Good luck > Although switching mould inhibitors can be a good way of losing contaminating bacteria (we too use the acid mix), take care NOT to use BOTH nipagin and proprionic/phosphoric acid inhibitors together. That prevents live yeast growing at all. Also, the active mould inhibitor is free proprionic acid. The phosphoric acid serves to reduce the pH to 4.0 so the proprionic acid is unionised; the amount of the former one needs to use will depend on the food recipe and ingredients and maybe should be roughly titrated the first time around. David Ish-Horowicz David Ish-Horowicz ICRF Developmental Biology Unit, Oxford d_horowicz@icrf.icnet.uk .