In this article we will discuss about the economic uses of babul.
1. Tannin:
Babul bark is the most important tanning material of northern India and is used in village tanneries from Haryana to West Bengal. A large quantity is consumed by the tanning industry in Kanpur. Babul bark is obtained mainly as a by-product when trees are felled for timber or fuel.
It is separated from the logs by beating them with wooden mallets and the strips thus obtained are dried in the open, chipped into smaller pieces and sent to the tanneries without any grading.
The proportion of bark to wood is roughly 1:5 by weight; and a plantation of c 620 trees per hectare, when 15 years old, may be expected to yield c5 tonnes of bark. The tannin content of the bark varies considerably; sometimes it is as high as 20 per cent, but on an average, the bark delivered to the tanneries contains much less tannin, c12 per cent.
It decreases somewhat during storage. The bark from older trees, though richer in tannin, is likely to be of high colour. The bark from branches yields 7-12 per cent tannin. The deep colour and high non-tan content of the bark are serious disadvantages.
Several polyphenolic compounds have been reported to be present in the bark and those identified are (+)-catechin, (—)-epicatechin, (+)-dicatechin, quercetin, gallic acid, (+)-leucocyanidin gallate, and two polymeric tan fractions, T1 (Butanol solubles) and T2 (Butanol insolubles) which form almost the entire tanning material component responsible for the tanning potency of babul liquor, with fairly good affinity towards hide powder.
The polyphenols of the bark are fungi-toxic and it has been shown that the lower molecular weight polyphenols are mainly responsible for this activity. The bark also contains sucrose.
Leather made from babul bark is firm and durable, though, harsh and dark coloured. Babul tannin is very good for heavier leather. In combination with myrobalans, babul gives excellent finished leather. Also, it was found that pre-treatment of the leathers with myrobalans followed by tanning with condensed tannins, including babul tans, reduced the time taken for penetration of the tanning materials and also most of the properties of the pre-treated leathers were found to be better than those tanned directly.
A blend of 2 parts of babul and 1 part of myrobalans was used in tanning to produce E.I. leather kips. The kips produced have been found to be satisfactory in colour and yield.
2. Timber:
The sapwood is wide and whitish; heartwood pinkish white to light red when first exposed, turning reddish brown with age, generally mottled with darker streaks. The wood is dull with somewhat rough feel, without characteristic odour or taste, moderately heavy to heavy (sp. gr, c0.8; wt. 817-865 kg/cu m), straight- or somewhat twisted-grained and coarse-textured.
It provides a very strong and hard timber. The wood seasons well even in the log and are moderately refractory. It is liable to split in the hot weather, and should be converted under shade.
The timber is fairly durable if well-seasoned; it is easily treatable under the open tank process. Heartwood is not readily attacked by white ants. It is hard and tough, and somewhat difficult to saw. It works well by hand, finishes to a good surface, takes a fair polish, but requires a good deal of filling.
The data for the comparative suitability of the timber, expressed as the percentages of the same properties of teak, are – wt. 118; strength as a beam, 93; stiffness as a beam, 84; suitability as a post, 82; shock-resisting ability, 126; retention of shape, 83; shear, 151; hardness, 135; and nail- or screw-holding property, 113.
Babul is one of the favourite timbers for native wheelwright work, being used for felloes, spokes, naves and axles for the bodies of carts, and also for shafts and yokes. It is used for agricultural implements such as ploughs, harrows, clod crushers and Persian wheels.
It is also used to make well curbs, tent pegs, boat handles, knees for boat-building, oars, sugar- oil-presses, bedsteads, railway wagon buffers, hookah—stems, tops, dies for cloth stamping, walking—sticks, and for carving and turnery. It is suitable for hammer handles and is used by the railways for anvil blocks and railway keys.
It was tried in power transformers, but found unsuitable; its dielectric strength (a specimen from Raipur) was found to be 5.4 kv/cm along the grain and 17.5 kv/cm across the grain with dielectric constants 3.20 and 2.06 respectively. The wood is in great demand for fuel. It has a calorific value of 4,224 cals.
3. Gum:
The gum of A. nilotica subsp. indica, although called gum arabic, is not the true gum arabic which is obtained from A. Senegal. In trade, in Bombay, three chief varieties are recognized- (i) True gum arabic, (iii) East Indian gum, and (iii) Indian gum arabic. Most of the true gum arabic, used in India, comes direct from Saudi Arabia and Africa. These imported gums are carefully sorted, cleaned and graded according to size and colour of the fragments.
The smaller pieces are pulverized and sold as powdered acacia gum. The smaller lumps and finer fragments are marketed under the names maklai or safed gundar. The East Indian gum is imported entirely from Aden and other Red Sea ports. It is hand-picked and graded in Bombay, and re-exported to Europe and America.
Indian gum arabic is the name given to the commodity of Indian origin. It consists of a mixture of babul and other acacia gums. Two varieties of this gum are known, viz. gum bavool and gum ghati. The former consists of acacia gums from A. nilotica subsp. indica, A, catechu and A. modesta. Occasionally, it is found mixed with gums from Anogeissus latifolia, Azadirachta indica and Feronia elephantum Correa. Gum ghati has only up to 40 per cent of acacia gums.
The gum exudes from wounds in the bark, mostly during March-May. Though some trees yield a maximum of c 1 kg per year, the average is only a few grammes. The yield lessens with the increase in age of the trees and it is believed that tapping accelerates the flow, but it is not often practised.
Babul gum occurs in the form of rounded or ovoid tears. Each tear is about a centimetre in size and the colour varies from pale- yellow to brown or almost black, according to the age of the tree and the conditions of collection. The crude gum is first broken into smaller pieces, cleared and carefully sorted according to size and colour. It is generally considered inferior to true gum arabic, especially for medicinal purposes. But if proper care is given to collection and grading, the gum obtained conforms to the B.P. requirements for acacia gum, except with regard to the optical rotation.
Babul gum is very slightly dextrorotatory, whereas the gum of A. Senegal is slightly laevorotatory. It contains 13 per cent of moisture and on ignition it leaves behind 1.8 per cent of ash (CaO, 52.2; and MgO, 19.7%). The gum contains galactose, L-arabinose, L-rhamnose, and four aldobiouronic acids, viz. 6-O-(β – glucopyranosyluronic acid)- D-galactose; 6-O-(4-O-methyl- β -D-glucopyrano- syluronic acid)-D- galactose; 4-O-( α -D-glucopyranosyluronic acid)-D-galactose; and 4-O-(4-O-methyl- α -D-gluco-pyranosyluronic acid)-D-galactose. The 3, 5, di-O-methyl-L-arabinose and a new crystalline arabinobiose, 2- O- β -L-arabinopyranosyl-L-arabinose (C10H18 O9. ½ H2O, mp 103°) have been isolated from the gum. It also contains arabinobiose, 3- O- β -L-arabinopyranosyl-L-arabinose.
Good quality babul gum is used in calico-printing and dyeing, as a sizing material for silk and cotton, and in the manufacture of paper. Generally, it finds application in all industries where a mucilage or adhesive is required. It is used as a substitute for true gum arabic as an adhesive, though its adhesive strength is somewhat lower. It is fried in ghee and used in the preparation of sweetmeats. It was tried as a possible ice cream stabilizer, and its effect on the flavour of plain ice cream has been examined.
Best results were obtained with the gum at 0.5 per cent level. Babul gum is used as a masticatory. It is not suitable for making European type of confectionery. In pharmacy, it is used as a substitute for true gum arabic, and in the indigenous medicine, it is credited with numerous virtues. It is useful in diarrhoea, dysentery, diabetes mellitus, sore-throat, etc. Inferior varieties are employed in the manufacture of matches, inks, distempers and certain types of paints and mortars.
Unfortunately, the collection of gum in India does not receive proper attention as it is entirely in the hands of ignorant people. The crude material, consisting of a mixture of various gums, reaches Bombay from all parts of the country, especially from the Deccan and the western regions, for marketing.