Dyeing Behavior of Silk Proteins in Relation to Silkworm Diet

We investigate the dyeing characteristics of silk proteins produced by silkworms reared entirely on an artificial (A) diet, and compare them with those of worms raised entirely on a mulberry leaf (M) diet. The artificial diet has tofu-cake as its main component. Two kinds of cocoons (A and M) are used as the original sample materials. The A and M raw silk samples are prepared from cocoon samples by the usual filature process. Sericin contents of the A and the M raw sill; samples are 26% and 21.7%, respectively. The A and the M fibroin samples are prepared from each raw silk sample by extracting the sericin proteins with 0.5% sodium carbonate at the boil for 30 minutes. Dyeing experiments on the raw silk and the fibroin samples using an acid dye (CI Acid Orange 7, 0-7) at pH 3.9 and 60 degrees C show that the dyeing rate and dye concentration on the A fibroin are almost the same as those on the M fibroin samples. On the other hand, dye concentration on the A raw silk is much higher than that on the M raw silk samples, meaning that the dye concentration on the A sericin is much higher than that on the M sericin.