Yellowing of Cocoon Filament Obtained from Silkworm, Bombyx mori Reared on Artificial Diet Containing Tofu-Cake Powder.

Abstract

Yellowing of two types of cocoon filaments was investigated. One type is the cocoon produced by silkworms reared with mulberry leaf diet at 4th and 5th instar (Mulberry sample). The other is that with an artificial diet containing Tofu-cake powder as a main component (Tofu-cake sample). The yellowing of Mulberry sample was remarkable after irradiation with ultraviolet light, while it was scarcely observed for Tofu-cake sample and the extent of yellowing decreased with increasing Tofu-cake content up to 50%. Tofu-cake sample contained relatively a large amount of nucleotide compounds, such as deoxycytidylic acid (dCMP) and cytidylic acid (CMP) in a hot-water-soluble fraction, and the contents of these compounds increased with increasing Tofu-cake content. On the other hand, Mulberry sample contained little amount of nucleotide compounds. The difference in the yellowing behavior between these two samples was attributed to the difference in the contents of nucleotide compounds. This was also confirmed by the fact that yellowing of Mulberry sample was drastically suppressed after immersing it in 3% dCMP aqueous solution.