Salai gum or Indian olibanum is the gum-resin obtained from the species of Boswellia of which Boswellia serrata Roxb. ocuurs in India.
Local names : Salai, luban, salga, shallaki, guggal, kundrikam, kungli, morada
Plant Source : Boswellia serrata
Family : Burseraceae
Distribution : It is a moderate to large branching tree, found in dry deciduous forests, being common in dry hills throughout India. It usually has a short bole, 3-5 m in length, sometimes longer if grown in a fully stocked forest. Bark is very thin, greyish-green, ashy or reddish peeling off in thin, papery flakes. The leaves are like those of neem plant and have small white flowers. The tree occurs mainly in Madhya Pradesh, Andhra Pradesh, Odisha, Rajasthan and Gujarat and to a lesser extent in Maharashtra, Uttar Pradesh and in other dry and tropical regions of the country.
The tree is characteristically found on the slopes and ridges of hills, as well as on flat terrain, attaining a larger size on fertile soils. It is resistant to drought and fire. The tree is also frost hardy and serves as a nurse tree for other species. It typically grows on rocky ridges and it does well on neutral soils above gneiss, schist, quartzite, limestone and sandstone. The species has the ability to thrive in the poorest and the shallowest soils where most of its associates remain stunted. Relative humidity should be 40.80% in the winter and 60.90% in the summer. The tree can be found up to 1150 m in elevation.
Production in India : 50 tons per annum (approx.)
Major producing countries : India and Pakistan
Method of harvesting/tapping: Usually trees of 90 cm girth and above at breast height are tapped for the gum-resin. Trees of lower girth classes should not be tapped since any damage done to them may adversely affect their growth. A thin band of bark of about 30 cm in length and 20 cm wide is shaved from the trunk of the tree at a height of about 0.75 meter from the ground. Thus the reddish phloem in which the resin canal and ducts lie is exposed. The blaze is freshened after every fourth or fifth day. The first collection of the gum-resin is made after 2 weeks. Collection is done by a scraper keeping a tray having a semicircular edge around the blazed surface. Freshening of the blaze is done from time to time and the original blaze is slowly widened.
Period of harvesting/collection : Tapping and collection of salai gum generally started from November and continued upto end of May every year. It closes on the onset of monsoon. The gum may be collected after a month of initial blazing. Subsequent freshening of the blazes and collection may be done fortnightly.
Yield : Average annual yield of salai gum per tree is estimated to be about 1 kg, though a well grown tree yields upto 2 to 2.5 kg of gum. resin in a year. The yield of salai gum is found to vary according to season, locality, and size of the tree. Generally larger the girth of a tree, the greater is the yield. Yield has generally been found to be poor in moist region and from trees which are old with black bark, dwarfed and suppressed. Middle aged, sound and vigorous trees give comparatively better yield.
Salai gum is collected in a semi-solid state. After collection, the bark and other impurities are removed manually. The crude gum-resin is allowed to remain in a bamboo basket for upto a month during which the fluid portion, locally known as ras, flows out. The as forms about 8 to 10 percent of the raw material and is used in paints and varnishes. Remaining semi-solid to solid part is the gum resin, which is dried thoroughly and sometimes treated with soapstone powders to make it brittle. It is then broken into small pieces by wooden mallet or chopper. During this process, bark and other impurities arc again removed manually. The gum-resin is then graded according to its colour and impurities. Generally four grades are distinguished in the market as follows.
Active Constituents :The gum oleoresin consists of essential oils, gum, and terpenoids. The terpenoid portion contains the boswellic acids that have been shown to be the active constituents in boswellia.