At 09:25 AM 4/3/00 -0700, Chrystal wrote:
>Purely on experience alone, I agree with Peter Howgate. The same
>"irridescence" effect is present is very fresh pollock fillets caught and
>processed at sea.
><snip>
>My explanation is that the rainbow colours derive from diffraction from
>the firous structure of the muscle. The parallel orientation of the fibres
>act as a grating. Best seen when the fish is very fresh and the fibres are
>intact with a large differential in optical properies between the fibres
>and the extracelular fluid. On storage this difference is reduced as
>concentrations inside and outside the cell equilibrate.
I'm still happier with the refraction argument I mentioned, instead of this
diffraction one. Several reasons:
1. Diffraction depends solely on the periodic physical layout, not on
differences in refractive index.
2. The diffraction argument would still apply to the dry muscle (i.e.,
moistness would not be required). An optical diffraction grating involves
only rulings, not a medium.
3. Diffraction is primarily a phenomenon of transmission, not reflection,
although I'll admit reflection effects are also possible.
4. Oil slick on water is the most common experience of iridescence. Is this
caused also by diffraction or simple refraction effects?
5. Iridescence is a common phenomenon on cooked, sliced ham. Blotting the
surface removes the effect. The muscle fiber alignment remains the same.
================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS e-mail: ral@lcfltd.com
Least Cost Formulations, Ltd. URL: http://lcfltd.com/
824 Timberlake Drive Tel: 757-467-0954
Virginia Beach, VA 23464-3239 Fax: 757-467-2947
"Vere scire est per causae scire"
================================================================
This archive was generated by hypermail 2b29 : Tue Apr 04 2000 - 21:57:32 PDT