Freeze-drying of fluorescent silk cocoons

Abstract

　　Hot air-drying, a widely used method for cocoon drying, uses multi-band progressive cocoon-drying machines. For hot air-drying, 115°C is recommended on contact with the cocoon. The finishing temperature should be reduced gradually from 60°C during hot air-drying.

　　Because the fluorescent color is eliminated by high-temperature treatment, the harvested cocoons were dried at 60°C for 24 hr. Fluorescently colored silk, cocoon drying, and cooking all constitute bottlenecks that impede efficient production. To alleviate those bottlenecks, we used a vacuum cocoon cooking machine for fluorescently colored silk. The machine has been semiautomated and scaled up to overcome the productivity constraints. Nevertheless, cocoon drying of the fluorescent colored silk was not improved. This report describes the performance of reeling tests and color observations of freeze-dried cocoons produced by fluorescently colored silk strains and a standard strain. Results demonstrate that the cocoon color of the fluorescent silk strains faded slightly and that the percentage of reelability was decreased.