Question

Which of the following is /are correct regarding preparation of silk?
A) We kill the larvae inside by a process called stifling by putting a lot of these in a steam oven for 10 to 15 minutes.
B) The cocoons have to be stifled to kill the larvae inside as otherwise; it will cut its way out after growing into a moth and spoil the cocoon.
C) We will not be able to get a continuous thread of silk from such a cocoon. Thus, we won’t be able to obtain quality fiber for fabric.
D) All of the above.

Answer 1

Hint:Cocoons when they are fresh, they posses live pupae in them, therefore they cannot be stored for long time, as the pupae might gets matured and transform into moths within 10-12 days which come out of the cocoon breaking them at one end, these cocoons are called pierced cocoons. Pierced cocoons are useless. Hence the pupae are killed without damaging the cocoon.

Complete step by step answer:
1) Rearing silk worms for the production of silk is named as sericulture. In sericulture the eggs of silk worms are bought by the farmer and grown by feeding them nicely with mulberry leaves.
2) The silk worms after they are completely grown they stop feeding and start to extrude its saliva and spins around itself to build a net for itself. The saliva of the worms contains fibroin protein; it solidifies when exposed to air.
3) This net which they have built for themselves is called a cocoon. After the cocoon is built the worm rests and goes into pupa stage which on maturation becomes a butterfly and comes out breaking the pupae. Which are called pierced cocoons.
4) Their pierced cocoons cannot be used for the production of silk as the continuity of the silk threads would have broken.
5) Therefore, the pupae should be removed without damaging the cocoon. Hence they are killed by a stifling process.
6) There are various methods of stifling, in industries sun drying and steam stifling are majorly used methods. Sun drying even though it is cheap, cannot be done in winter; hence steam stifling is a popularly used method. We know that steam is hotter than the boiled water therefore it can kill the pupae easily.
7) Steam stifling process: Here the cocoons are taken in a porous basket and kept in the steaming chamber for around 10-20 minutes. The pupae in them will be killed.

Note: Remember the cocoons in the pupae that are killed by the stifling process are not removed; they remain inside the cocoon itself. Therefore the bodily fluids of the dead pupae also remain there only and make the cocoons moist. Hence they are dried to evaporate the moisture and then silk is reeled from them.