Degumming/retting

The degumming (retting) of hemp is discussed in Section 2.2.4. However, research has been conducted on hemp fibre into new retting techniques. 

Degumming (retting) is the process of extraction of the fibre whereby jute stalks or crude ribbons are immersed in water for a certain period of time. Bundles are then submerged in water for 7 to 10 days. Retting takes place due to the joint action of water, aquatic and plant surface organisms, mostly bacteria in the begiiming the process is aerobic, later anaerobic. 

Although ramie fibre is usually degummed chemically, there have been promising developments in microbial degumming (retting). Additionally some researchers reports that the use of ultrasonic vibrations speeds up the degumming process. The enzymatic treatment seems to be promising. 

All parts of fibrous plant stem must be removed for proper fiber separation. Bast fiber extraction is usually conducted using special processes such as water and dew retting, degumming, or decortication, in which the separation of bundles craitaining elementary fibers joined together by pectin and calcium ions is also performed. Fiber content in the stem of fibrous plants is shown in Table 4.1. 

The process of loosening the bond between the fibre bundles and surrounding tissue (decomposing the natural adhesive pectin) is called degumming. There are several degumming methods (Fig. 2.2) however, only two are commonly used, water and dew retting. 

Both processes involve the action of enzymes used by retting organisms to dissolve pectin. Enzymes can also be used directly to degum the straw. For flax a pectolytic activity (°PM) of 210 U cm is required. 

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