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Dear Leigh,

We've done a little of this sort of thing for bread and for different
doughs.  For structure, freezing the material then either fracturing or
cryo-planing then observing frozen in the SEM worked reasonably well.  The
most critical part is working out how much to etch the sample before
coating.

Freezing and freeze-substitution before embedding might work too - less
likely to lose water-soluble components, and should get reasonable
preservation of structure in dryish material.  We've done this on
absolutely dry leaf and other plant tissues and it worked OK (long long
infiltration times.....).  Should still see autofluorescence in sections of
this material.

good luck!
Roseamry

>
>Was approached with an interesting problem.
>This may be off-topic but some one here might have had a similar
>problem.
>
>A lady wants to look at the physical characteristics of various "bread
>crumb" samples. Some of these are actually bread, some are potato and
>others are various weird things that food manaufacturers want to try for
>food coating.
>
>Now some of them have a sort of "frosted" appearance.
>She wants to find out if this effect is caused by air bubbles, crytsals
>beneath the surface or some other cause.
>
>She was originally talking about parafin sections but I thought that
>the material would be too hard to section in parafin. Thought about
>resin embedding but considered that the resin might displace any crytals
>and how would it be possible to discern whether a "void" is/was an air
>pocket or filled with some form of crystal that may or may not have been
>dissolved by the embedding.
>
>I did suggest that she might need subtle use of a form of
>autoradiography with extremely fine emulsion and ionising radiation,
>high resolution X-ray or NMR to stand a good chance of getting a better
>understaning of her samples.
>
>The thought of confocal imaging appealed to her due to the possibility
>of 3-D rendering.
>I did stick some of her bread crumbs under the Mercury Lamp and the
>ones I observed did autofluoresce.
>
>Now she is very keen to try this. I have advised her that I don't think
>confoca will get her the insight she requires but I am happy to take her
>money if she insists.
>
>She insists.
>
>So, has any done this sort of thing before?
>Ideas on strategy, sample preparation etc?
>Better suggestions for her?
>
>
>
>Regards
>
>Leigh Silvester
>Division of Animal Physiology
>University of Nottingham
>School of Biosciences
>Sutton Bonington Campus
>Loughborough
>Leicestershire
>LE12 5RD, UK
>tel: +44 (0)115 9515151 x18736
>fax +44 (0)115 9516302
>[log in to unmask]


Rosemary White          [log in to unmask]
Microscopy Centre               fax     61- 2 6246 5000
CSIRO Plant Industry            ph.     61- 2 6246 5475 or
GPO Box 1600            mob.  61- 0402 835 973
Canberra, ACT 2601, Australia