Process of extraction of katha from Acacia catechu

Extraction of Katha from Acacia catechu

(Based on a conversation with Chandra Narayan Nidhi, Pashupati Katha Mills, Simara)

    The most important product obtained from Acacia catechu is Katha or catechu. Katha is generally extracted from the heartwood of  Khair(Acacia catechu) belonging to family Leguminosae. This is obtained by boiling chips of heartwood with water.
The yield of Katha and cutch varies considerably with the season in which the trees are felled

and their girth, age and condition. The maximum yield of Katha is obtained from trees felled in autumn and winter. Trees that are gnarled and crooked are reported to give higher yields than a straight one. Trees of higher girth having white lines on them are preferred. Freshly felled trees also give higher yields than dried ones. Dead trees are unsuitable for extraction.

Heart wood of Khair.

The extraction process involves the following steps:

Removal of bark and heartwood:

For the extraction of katha, only heart wood is necessary. So the sap wood and bark of Acacia catechu is removed by the help of machine called debarker. The heart wood is converted into billets by bent saw and then shifted to next compartment for further processing.

Heart wood after chipping.

 Chipping:

The billets are transferred to chipper machine that converts the billets into small chips. These chips are approx. 2" to 5" in length.These chips are transferred for further processing. (Figure).

 Autoclave (Water extraction):

The chips are put into a pressure chamber called an autoclave. This chips are boiled with water, where pressure and temperature is maintained (150^oC) with respect to air pressure. This leads to the extraction of hot liquid.

An autoclave for katha extraction.

 Evaporator for concentration:

A concentrating chamber

The liquid extracted from autoclave is moved to next chamber, called evaporator, in which the concentration of liquid gets increased.

The concentrated material gets crystallized, through the cooling process.

  Filtration, plating and cutting:

The rectangular pieces are made and pressure is given to it. The liquid substance called kutch emerged out as a by-product. The rectangular pieces are cut into biscuit like shape, called katha.

  Drying:

 Katha are dried into a drying chamber for 15-20 days in cold air. The moisture gets reduced in this chamber.

 Ambient drying:

This is the last stage of extraction of katha. This chamber includes hot air which hardened the katha. After the ambient drying, it gets ready for packing.

  Packing:

 At last katha are packed in a carton and sold to market of India. The present market rate of katha in Nepal  is Rs.1000/kg.

Uses Of katha and kutch:

There is a very large internal demand for it for masticatory use in pan preparations and in medicine. Katha is regarded as astringent, cooling and digestive and is useful in sore throat, cough and diarrhea.

Externally it is employed as an astringent and as cooling application to ulcers, boils and eruptions on the skin. It is an indispensable ingredient of pan preparations. In combination with lime, it gives the characteristic red colouration resulting from the chewing of pan.

Dark catechu or cutch, which is mainly obtained as a by-product of the katha industry is marketed in the form of small cubes or blocks. It is used only for industrial purposes. It is largely used for dyeing cotton and silk and preserving of fishing nets, sailing ropes and mail bags; in water softening and in the manufacture of stencils and printers ink.From Nepal, It is mainly exported in Bangladesh. The current rate of kutch is about Rs.50-60/kg.

Some Photographs:

(Photos were captured on Pashupati Katha Mills, Simara, Bara by R.C Awasthi)

1. Workers busy in extraction process.

2. Katha extracting in liquid form.

3. Heating chamber 

4. Solidified katha.

5. Katha in drying chamber.