Heat treatment of cocoons silkworms and its effect on stifling pupae's and quality of the produced silk fibers [electronic resource].

Includes references.

To export or store cocoons mulberry silkworm yield for a long time, cocoons must be dried to stifling the pupae inside the cocoons and to reduce the high moisture levels of cocoon shell and pupae body to a safe moisture level. This safe level should be low enough to reduce fungi and microbial growth, which cause decomposition and affecting the quality and appearance of the silk fiber. The aim of this research work was to study the effect of heated air treatment of cocoons silkworms on the stifling pupae's inside cocoons and quality of the produced silk filaments. A small portable batch dryer suitable for small Egyptian rearer’s silkworm was used. This system was compared with the conventional method for drying and stifling pupae's in Egypt. The experimental treatments included four different levels of heating air temperature (55, 65, 75 and 85 °C), and three different levels of air flow rate forced through the cocoons (1.0, 1.5, and 2 m3/min). The obtained data showed that, during the conventional sun drying, the cocoons moisture content decreased gradually from initial moisture of 64.5 + 0.5% (w.b) to a final level of 10 + 1.0 % (w.b) after 4.5 days (60 h). While heating cocoon artificially at air temperature of 85 °C and air flow rates of 1.0, 1.5 and 2.0 m3/min reduced the drying time by about 91.6, 92.5 and 94 %, respectively, as compared with the traditional drying of cocoons (control treatment). On the same time, the maximum value of the killed pupae's, length of silk filament, silk filament strength and cocoons reel-ability was always obtained at treatment of 85 °C air temperature and 2 m3/min air flow rate. At this treatment, the highest values of the killed pupae (99.35 %), silk filament force (18.8 cN/tex), and elongation of silk filament (11.83 %) were achieved. This resulted in highest value of cocoons reel-ability (67 %) and highest length of silk filament (930 m). The drier may be offers a substantial increase in the price of silk filament (higher categories price) by decreasing the total reeling losses, and consequently increase the yearly economic return.

Summary in Arabic.

1