The process
of separation and extraction of fibres from non-fibrous tissues and woody part
of the stem through dissolution and decomposition of pectins, gums and other
mucilaginous substances is called retting.
- Jute fibre quality depends to a large extent on the bio-chemical process of retting.
- Improper retting may lead to inferior quality of fibre in spite of good crop which ultimately may face lower price in the market and lower net return to the farmers.
- Jute consists of cellulose cemented by non-cellulosic materials such as pectin, hemicelluloses, etc. These so-called cementing agents are removed by the enzymes produced by microbes in the process of retting. The decomposition of free sugar present in jute and mesta plants takes place at early stage of retting followed by pectins during middle stage, and hemicellulose, sugars and nitrogenous compounds (mainly proteins) at later stage of retting.
- The retting water becomes acidic at later stage of retting due 8 to the presence of organic acids (acetic, lactic, butyric, ketoglutaris), acetone, ethyl alcohol, butyl alcohol and various gases
Demerits of
Retting:
- Retting duration is very long
- Longer retting duration encourages over retting resulting less fibre recovery from top portion of the plants.
- The fibre is black in colour with poor lusture.
- The strength of fibre is very poor.
- Because of lower fibre quality, farmers get low price for their fibre in the market
- Most of the fibre produced by this method is unsuitable for production of high valued diversified products.
Do’s of
retting:
- Harvesting of jute plants should be done at proper stage of maturity between 110 to 120 days for quick retting and quality fibre production. Over-aged plants take longer period for retting with deterioration in fibre quality.
- If possible jute plants should be sorted in thick and thin diameter of stems before retting, it will prevent the over retting of thin plants.
- Defoliation prior to retting will reduce transport and handling charges and return organic materials to the soil and reduce the amount of organic load discharged to the retting waters.
- Keeping dhaincha (Sesbania aculeate), sunnhemp (Crotalaria juncea) plants and Gliricidia leaves as covering materials or in between the jak reduced the retting period by 3-5 days.
- Retting should be done in free flowing water. If free flowing water is not available retting should be done in stagnant water and water should be non-saline & clean.
- The volume of water should be enough to allow the jute bundles to float.
- The minimal volume of water used for retting should be such that the jak is submerged completely in water and there is 4 inches of water above the upper layer of jak.
- Jute bundles when immersed in water should not touch the bottom or ground.
- Concrete block, wooden log, old cement bags filled with sand, mud or stone can be used as covering materials for proper immersion of jute bundles in water
- Periodic checking of jute bundles kept in retting tank should be checked for extraction of fibre in proper time and to avoid over retting.
- Extracted fibres should be washed in clean water.
- Fibres should be dried properly under the sun in a bamboo-frame.
Don’ts of
retting:
- Do not keep the jute plants in the field beyond 120 days, harvesting of jute plants beyond 120 days of crop age will delay the retting as well as deteriorate the quality of fibre.
- Do not use mud or banana plants to cover the jute bundles/ jak for retting as it will end up giving black color to the jute fibre also known as Shyamla.
- Do not use excessive amount of water to submerge the jute plants as it will delay the retting process.
- Do not over - ret jute plants. Over-retting of jute will produce inferior quality of fibre and thus the price of the product will decrease.
- The same retting tank or ditch should not be used for retting when water becomes dirty and addition of fresh water is also not possible, otherwise it will lead to the production of very inferior quality fibre.
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