Influence of Tobiko-Mixed Artificial Diet on Textile Properties of Bombyx mori Silkworm Cocoons

Abstract

ABSTRACT We attempted to use tobiko powder, a byproduct of the konjac cake production, to rear the 5th-instar silkworms by mixing it in the artificial diet, and found that tobiko powder was usable up to the mixing ratio of 20 wt%. Even when the content of mulberry leaf powder in the diet was decreased down to 10 wt% with inversely increasing the tobiko powder up to 20 wt%, the 5th-instar silkworms yielded cocoons comparable to the conventional rearing. However, the spinning habit of the silkworm was a little modified probably by the bioactive chemicals contained in the tobiko powder. Further, yellowing occurred on the surface of the trial raw silk fibers, suggesting that some substances contained in the tobiko powder were excreted in the sericin layer of the cocoon threads. Such change in the composition of sericin layer effectively promoted the enzymatically degumming and then, a glossiness of the degummed fibers was enhanced due to the formation of the fibrillary lines passing along the fiber axis on the fiber surface. In addition, WAXD analysis revealed that the crystallinity of the trial fibers was a little superior to that of the conventional fibers.