Lecture No.34

Post cocoon technologies and byproducts of sericulture

Post cocoon technologies

With the harvest of cocoons, ends the sericulture part and begins the industrial part of

the silk industry. However, since production of silk is all that the sericulture is about, we

cannot ignore the events that meet the cocoons after they have been harvested. The events are

I . Stifling , II.Boiling III.Brushing, IV Reeling , V Re-reeling, V1.Finishing

and VII. Testing

The cocoon of B.mori is made up of a single long thread of fibrion held together by the

cementing protein sericin, along with trace amounts of ash and colouring matter.

I. Stifling

Once the moth emerges, the cocoon becomes unsuitable for reeling as the continuous

thread breaks into pieces. Therefore, the first step upon arrival of the cocoons at the reeling

units is killing the pupae. This process is called stifling. The pupa has to be both killed and

dried because a dead but wet pupa will undergo decomposition and the decomposition

products will spoil the cocoons. There are three methods of stifling viz.,

a.Sun drying

The cocoons are exposed to the scorching action of direct sunlight for tow to three days to

kill the pupa and dry the cocoon (stifling).

b.Steam stifling

Hot and wet steam is used to kill the pupa inside. Unlike sun drying, stifling can be

done in all seasons. Also the cocoons are stifled more uniformly and quickly. During stifling

the cocoons must be exposed to steam uniformly on all sides.

c. Hot air steaming

The compactly built cocoons require a very long exposure to steam to achieve complete

stifling of the pupa and an equally long time for drying. Hence, for these hot air is blown over

cocoons for stifling and drying simultaneously. The hot air method is used for stifling a large

amount of cocoons in a short time and storing them for longer duration.

II.Cocoon boiling

The silk bave is wound and gummed together by sericin to form the cocoon shell, the

sericin binding it has to be removed. Since sericin is soluble in hot water, the cocoons to be

reeled are first immersed in hot water for partial dissolution of the sericin to facilitate

unwinding the silk fibre. This process is called boiling or cooking.

III.Brushing

After the cocoons are thoroughly cooked, they have to be brushed to remove the floss

layer. In the open – pan system, brushing is done along with cooking while in the three pan

system and in the sunken system it is done separately.

In the Indian charka reeling unit, the floss layer is removed individually from each

cocoon by peeling with the hand, a single stick or a prong made of two twigs or sticks.

IV.ReelingThe silk filament of each cocoon is too thin to be used directly and hence filament from a

number of cocoons ( the number depending on the size of silk desired) are combined and

unwound together and the resultant yarn wound onto a reel.

Two systems are used for reeling of silkworm cocoons

V.Rereeling

When it is directly reeled on standard reels as in the charka, silk suffers from certain

defects such as short lengths of fine size, broken threads, entanglement, hard gum spots and

split ends. These make for wastage during the later operations of silk throwing and twisting.

To avoid these defects, most reeling units practice indirect reeling where actual reeling is

done on small reels and the silk later transferred to standard size hanks; this process is called

rereeling.

VI. Finishing.

In this process, the visible defects of the raw silk thread – like oversize knots, loose ends

etc., are removed and the silk is boiled, stretched, purified by acid or fermentation and

repeatedly washed to bring out the luster or glass characteristic of the silk. The threads are

then changed into bundles or skeins.

VII.Testing

There are Indian and international standards to judge the quality of the raw silk and facilitate

its marketing. To maintain these standards, raw silk is put to a number of tests to assess its

size variations, winding quality, neatness, evenness, cohesion and tenacity.

Byproducts of sericulture

Sericulture involves three major activities viz., production of mulberry leaves

(Moriculture), rearing of silkworm and reeling and its processing activities. Certain amount

of by product wastes are generated at each stage.

The by products are classified into:

i) Byproducts of mulberry Mulberry leaves wood, fruits and roots

ii) By products of silkworm rearing

Silkworm letter, bed water, faeces, pupae, unused cocoons (pierced cocoon, melted cocoon, floss double / flimsy / stained cocoons)

iii) By products of silkworm reeling / post cocoon stage

Cooking wastes, reeling wastes, palade layer, half reeled cocoons, unreelable cocoons, pupae, charka wastes;Wastes generated during silk winding, spinning, weaving, re-reeling wastes, twisted silk, silk wastes, silk noils.

Source and utilization

A. Mulberry

Mulberry leaves: In addition to being mainly used as feed for silkworm, the leaves can be

utilized for cattle feeding preparation of chlorophyll, soap, Cosmetics, hair oil and mulberry

tea. Leaves also hold pharmaceutical value as they have diuretic and ant diabetic properties.

Mulberry stem / wood: It is used as a fuel wood and fuel and in the preparation of sports

goods toys fine quality papers and collection of edible fungus. Tannins extracted from stem /

bask can be used as a colouring agent.

Mulberry roots:

Blood pressure can be lowered by using the constituent of surface of mulberry roots

which is soluble in water and in alcohol

Mulberry fruits: They are used for preparation of juice, jelly, squash and jam.

II. Silkworm rearing/ reeling products

1. Silkworm litter:

It is used in compost making, biogas production and also for used as cattle and poultry

feed. Chlorophyll paste, proteins and plastic materials cab be prepared from it.

2. Silkworm faeces:

It is generally considered as waste. It is mostly used in compost / vermin compost

making as cattle feed. It can be used as aqua feed and for preparation of chlorophyll paste.

3. Pupae:

Silkworm cocoon consists of two major portions viz., cocoon shell (12.24%) and

pupae (76 – 88%). Dried pupae contain 28.4% oil and 51.3% protein is used for the

manufacture of pupal oil, Amino acid powder, peptides / protein concentrate.

The pupal oil which is brown in colour with bad odour finds limited use in the

manufactures of industrial soap. It finds use in the preparation of cosmetics, lotions, cream

and shampoo etc,.Two pupal oil extract units are functioning at Mysore and Kallur (Andhra

Pradesh)

The pupal wastes after extraction of oil can be used as poultry / aqua feed. Pupal fat is

a good raw material for manufacture of glycerin soap and cosmetics protein of pupae is better

than of soya / fish.

4. Pupal skin

It is available in the reeling and grainage as wastes. It is made up of chitin (3 –4 % of

dry weight of pupae). It is used as an additive to increase the loaf volume of wheat bread

from 4.6 to 6.0 an3 /g.

5. Basin refuse

The last layer of cocoon attached to pupae (palade layer) can not be reeled. This can

be used for manufacture of Spun silk which will reduce the cleaning cost of pupal wastes

6. Cut and pierced cocoons

Cut and pierced cocoons can be used for the production of hand span yarn (matka)

using takli ; such units are functioning in Malda, west Bengal.

7. Noil yarns

First quality of wastes obtained during the processing of spun silk yarn is utilized for

production of ‘Noil yarn; which is used for the manufacture of carpets.

8. Twisting / Throwers wastes

Waste silk obtained during winding, twisting and doubling of yarn are used for

production of thick fabrics / carpets.

III. Therapeutic/Pharmaceutical value of mulberry / silkworm

A. Mulberry

Mulberry contains all the essential and non essential nutrients required by man kind.

Mulberry leaves are rich in glucose, fructose, sucrose, dextrin, galantine and crude

fibres. Mulberry is having high nutritive value with vitamins, A, b, B2, B3, B5, B6, B8, B9,

chlorine and Inositol, vitamin C, D,E . It possesses healing properties and it is

comparable to that of Spinach and is more palatable. Mulberry can be used for

protein supplementation diet and smooth.

Mulberry tea is reported to reduce blood pressure.

Mulberry fruit juices can be used for curing sore throat fever and diseases like

dyspepsia, melancholia (depression disorder).

.Deoxy nojiri mycin (DNJ) an alkaloid extracted from the roots of Morus nigra acts

as a hormone inhibitor / anti diabetic.

Mulberry bark is effective as a purgative and vermicure.

Mulberry fruits contain flavanoids and it can be used to impart flavour and colour to

medicated syrups. Mulberry fruit juice has antipyretic property.

Mulberry roots have anti diabetic properties. (it has the effect on pancreas

glycogenolysis). Alkanes, B-amurine, B-silosterol and other alkaloids possess

antipyretic and anti diabetic value.

Root bark contains calcium malate, phlohapheres, phytosterol, fatty acids and

phosphoric acid. Root contain anti helminthic property.

B. Silkworm

Silkworm pupa is a rich source of proteins and amino acids. Chitin is used for post

operative treatment of intranasal operations. Chitosan is a biocompatible membrane

to check bleeding in major surgeries.

Silkworm pupa production is 3-4 times that of raw silk production by weight and it

can be used for by product generation besides reducing environmental pollution way

of waste disposal.

Silk has 17 amino acids exactly as that of hair and hence it is used for moisturizing

condition agent in shoot as it can revitalize the hair.