and tachysterol2 were found. The quantitative differences from
species to species may be explained by the metabolic interrelationship
of the photoproducts: pre-ergocalciferol is precursor not only
to vitamin D2, but also to lumisterol2 (ring closure) and tachysterol2
(E/Z-isomerisation). Hence, the reaction rates to and from
pre-ergocalciferol affect the spectrum of products formed. In the
oyster mushroom the concentration of pre-ergocalciferol increased
smoothly, possibly because of the large stock of ergosterol (Fig. 2).
In this batch the concentration of 22-dihydroergosterol was
511 ± 23 lg/g dry matter at 0 min, and showed smaller irregular
increases and decrease over time to end at 405 ± 10 lg/g dry matter
after 60 min indicating dynamic equilibria between the photoreaction
products.
Confirming previous results with Agaricus (Roberts, Teichert, &
McHugh, 2008), the subsequent storage of illuminated fruiting
bodies of the oyster mushroom for a period of 5 days at 8 C
showed a steady, but slow decrease of the vitamin D isomers accumulated.
No discoloration or other sensory noticeable changes
were observed compared to untreated mushrooms.