SUSTAINABLE UTILIZATION OF GUM AND RESIN BY IMPROVED TAPPING TECHNIQUE IN SOME SPECIES

Mr. Balakrisnan NAIR
Department of plant sciences, Peermade development society, IDUKKI, Kerala
India

Summary

Gums and resins form an important group of non-wood forest products. The industrial applications of gum and resin have expanded tremendously in recent years. They are used in many unrelated industries such as paper, textile, petroleum, pharmaceutical, cosmetics, food, varnishes, lacquers and soaps. Even though gum is produced by a large number of plants, their commercial exploitation is restricted to members of the Leguminosae, Sterculiaceae and Combretaceae. Gum is also extracted from seeds, seaweed and microorganisms. Resins are obtained from members of Pinaceae (rosin, amber), Leguminosae (copal), Dipterocarpaceae (dammar), Burseraceae (elemi, frankincense, guggul) and Umbelliferae (asafoetida, galbanum). Gums and resins are considered as the byproducts or end products of certain metabolic pathways. Poor soil, drought and other hostile situations promote the production of gums and resins. Indonesia, India, China and Sudan are the major producers of gums and resins. Millions of people worldwide, especially in developing countries depend on collection of gums, resins and latex as a means for their livelihood. However, the market of these products has declined over years due to several reasons. The main reasons of this decline are the unscientific and brutal methods of tapping, over exploitation leading to the death of the tapped trees and erratic supply of these products in the market. Commercial tapping of gum and resin is done by blazing, peeling or making deep cuts on the bole. On account of injurious and wasteful tapping and over-exploitation the populations of gum and resin producing plants have markedly declined. On the absence of cultivation of these plants there is a grave concern about the loss of the wild germplasm. Simple and effective tapping techniques which ensure optimum yield and regeneration of tapped trees have been developed for gum Arabic (Acacia senegal), gum ghatti, (Anogeissus latifolia)), neem gum, (Azadirachta indica), guggul (Commiphora weightii), and gum karaya (Sterculia urens) which ensure sustainable production of these material. The details of these methods are discussed.

Keywords: Gums, resins, non-wood forest products, improved tapping technique, ethephon.

Introduction

Products from plants such as tannins, rubber, gums, gumresins, resins, essential oils, honey, medicines, fodder, wild fruits and several other materials were classified as minor forest products. These are presently grouped as non-wood forest products and have immense application in the industry, and also provide livelihood to millions of rural poor. Gums and resins form an important and widely used group of non-wood forest products, and are principal components in food and pharmaceutical industries. The world market for gum only as food additives is over US $ 10 billion in 1993 (Coppen, 1995).

Natural gums (gums obtained from plants) are hydrophilic carbohydrate polymers of high molecular weights, generally composed of monosaccharide units joined by glucocidic bonds (Davison, 1980). They are generally insoluble in oils or organic solvents such as hydrocarbons, ether, or alcoholes. Gums are either water soluble or absorb water and swell up or disperse in cold water to give a viscous solution or jelly (Mantel, 1949). On hydrolysis they yield arabinose, galactose, mannose and glucuronic acid.

Based on solubility in water gums are classified as (1) soluble, (2) insoluble and partially soluble gums. Certain gums dissolve in water to form a transparent colloidal solution (e.g. Gum Arabic). Gums such as gum tragacanth, gum karaya do not dissolve in water but swell up into a jelly-like mass. However, if sufficient amount of water is added they yield a thick transparent solution. Partially soluble gums first form a swollen jelly by dispersing in water and become solution on addition of more water. Mogador or Morocco gum (from Acacia gummifera) is an example of partially soluble gum.

Resins are polyterpenes and their acid derivatives. They are oxidation products of terpenes in all manners of incomplete stages. Resins are very complex chemical compounds and are soluble in organic solvents. They do not have affinity for water. The less soluble resins can be made to dissolve by a process known as ‘running’ or sweating (Mantel, 1950). When the resins contain essential oils, they are called oleoresins or soft resins. Gumresins are a combination of resins and true gums with a mixture of characteristics of both. Certain gumresins contain small amount of essential oil. They are called oleo-gumresins. Small quantities of resins exude on the surface of the trunk due to injury by wind, fire, lightening or wound caused by animals. However, for commercial purpose tapping is necessary. Sometimes the natural exudation is so copious that the resins becomes buried and fossilized in the soil around the trunk. Vast deposits of resin may be found where the original forest has disappeared. Amber is an example of fossil resins.

Gums are produced by members of a large number of families but commercial exploitation is restricted to a few species of Leguminosae, Sterculiaceae and Combretaceae (Table 1). Gum is also extracted from seeds (Table 2), seaweeds(Table 3) microorganisms (Table 4), and Aloe barbadensis (aloe gum) wood chips of Larix occidentalis (stractan), seed coats or barns of corn, wheat, oats, barley, rice and soybean (Hemicellulose). Resins occur in a wide range of plants. They are formed in the specialized structures called ducts. With the exception of Lac produced by the Lac insect (Laccifer lacca) all the natural resins are of plant origin. The important commercial resins are obtained from Pinaceae (rosin, amber), Leguminosae (copal), Dipterocarpaceae (Dammars), Burseraceae (elemi resins, guggul, frankincense) and Umbelliferae (asafoetida, galbanum) (Table 5). Amber and copal are the hardest resins, Elam and pine resins are soft and while resin form Rhus vernicifera is liquid and is used as natural varnish.

Table 1. List of a few plants, which are commercially tapped for, gums with their product names

Formation of gums and resins

Natural gums and resins are present either in the intercellular space (ducts or cavities) of the plant parts or as exudate produced due to injury. The ducts or cavities formed due to injury are called traumatic ducts/cavities. The causes of gum and resin formation and their biosynthesis are not fully understood. Poor soil, drought and other hostile environmental conditions promote their production. Gums and resins do not re-enter the metabolism of the plant in which they are produced and therefore, they are considered as by-products or end products of certain metabolic changes. It is suggested that gum formation may be a pathological response of the plants to protect the injured part by sealing the region to prevent water loss and infection. The development of the duct is schizogenous (separation of the duct initials by dissolution of middle lamella), schizo-lysigenous (separation of the initials followed by lysis of epithelial cells) and lysigeneous (separation of the duct initials followed by lysis of epithelial cells) and lysigeneous (death of the initials). The secretion may be eccrine (the secretory products are transported out of the cytoplasm as individual molecules against the concentration gradient by membrane-bound molecular pump with ATP supplying the energy, granulocrine (through vesicles formed from golgi bodies or ER) and holocrine (by lysis of the whole cell).

Table 2: List of plants which yield seed gum

Table 3: List of a few seaweeds used as sources of gum

Table 4: Biosynthetic gum (microbial gum)

Table 5: List of a few plants which are commercially exploited as sources of gumresins and resins with their product names

India, Indonesia, China and Sudan are among the major producers of gums and resins.

Uses of gums and resins

Use of gums and resins by human goes back to remote times. Gum Arabic has been used at least 4500 years before (Davison, 1980). It was shipped as an article of commerce by Egyptian fleets. Ancient inscriptions make frequent mention of gum Arabic called ‘kami’, which had been used as textile adhesives and in painting. Egyptian (Third dynasty, B.C.2650) used gum Arabic for wrapping mummies. Guggul was used as medicine about 5000 years ago. The earliest reference of medicinal and therapeutic properties of guggul is in Atharva Veda. Detailed account of guggul as a drug is given in the treaties of Charaka (B.C.1000), Sushruta (B.C.600), Vagbhata (17 century AD) and various Nighantus written in India during 12 to 14 centuries (Kumar & Shankar, 1982; Satyawati, 1991). Frankincense or olibanum from Boswellia cateri is referred to in Bible as a source of incense. Trade in medicinal and spicy resins like asafoetida, galbanum and ammoniacum was practiced by ancient people (Howes, 1950). The industrial applications of gums and resins have expanded tremendously in recent years. They have been used in many unrelated industries. Some important uses of natural gums and resins are given below.

Paper industry

Gum prevents dilatancy at high shear, helps regular distribution of pulp fibres, increases mullein-bursting strength, pick and retention of fibres, decreases porosity, fast crush, and improves surface properties, finish, ink acceptance and smoothness.

Textile industry

Gum is used as a thickening agent for pigment in printing fabrics. It prevents migration of dyestuff in pad dying operations, and produces very fine line prints with good definition and excellent washout.

Petroleum and gas industry

Gum is used as a component in drilling fluids, removing calcareous deposits, acidizing wells and secondary recovery of oils.

Pharmaceuticals

Gum tragacanth is superior in pharmaceutical applications. Gum is used as suspending agent for insoluble drugs, demulcent agent, emulsification, antiseptic preparations, binder for tablets and tablet coating, jelly lubricants, spermicidal jellies and to mask the unpleasant taste of syrups. It is also used as a medicine for treatment for low blood pressure caused by hemorrhage or surgical shock.

Cosmetics

Spreading properties of gums add smoothness to the skin and forms a thin protective coating. They are used for preparation of facial masks, foam stabilizer, production of liquid soaps, lotions, protective creams, face powder, tooth paste, mouth wash and hair cream.

Food industry

Of all polysaccharide consumed by human being, starch is the principal metabolizable energy source. The vast number of other polysaccharides consumed as natural compounds of edible vegetable, fruits and other material pass through the gastro - intestinal tract with little or no change. The intake of low concentrations of hydrophilic polysaccharides such as gum is beneficial as it will increase the bulk of intestinal content and also prevent excessive absorption of fats. Gums have been used in food industry in various ways. Even though they are used in low concentrations they impart important properties to the product.

The major functions of gum in the food products are gelling and thickening. As gums are water soluble or water dispersible hydrocolloides, they usually posses suspending, dispersing and stabilizing properties and therefore, acts as emulsifiers, coagulants, adhesives, binding, bulking, encapsulating, flocculating, gelling, suspending, clarifying, swelling, thickening and whipping agents, crystallization inhibitors, film formers, stabilizers and protective colloids.

Flavour fixation

Several powdered flavours are prepared dry to meet the specific requirement of food products such as pudding, desserts, cake, soup and beverage mixes. These products are manufactured by spray drying methods. Spray drying is done usually after the oil flavours are emulsified in gum solution. The flavour is “sealed in” in particles of varying sizes (1–50 (m). They are released only after they come in contact with water. Gum Arabic is preferred in citrus oil flavour. Generally the ratio of gum to flavour is 4:1.

Confectionery

A large part of gum Arabic is used in confectionery products to prevent crystallization. The gum also emulsifies and evenly distributes the lipid compounds. It retards fat accumulation on the surface in caramels and toffees. Candy jellies (contain 50% less sugar than hard candies) such as jujubes, fruit gums, fruit pastilles and gumdrops are manufactured using gum. The gum gives them a clear and finer taste. Sugar coated confections made by panning process employ gum to provide adhesive and firm coating for nuts. Gum also acts as a whipping and stabilizing agents for aerated confections such as angel kisses, marshmallows, soft caramels, nougats and meringues.

Dietetic food

Gum is used as a bulking agent and for the preparation of special purpose food (those for diabetics). A mixture of gum Arabic and xanthan is used in making stabilized, whipped or aerated low caloric products such as butter, margarine, toppings, spreads and frozen desserts.

Bakery products

Gums extend the shelf life of bakery products. It is used for bun glaze, and gives the dough good water holding capacity and less flabby appearance. In cake and biscuits the gum gives softer and better texture. It is also used as a component in topping and icing bases, emulsifying powder, encapsulating flavour, dispersal of vegetable fats and flavour release at specific melting temperature.

Beverages

Two different gums have been generally used in combination as emulsifier in many flavour emulsions such as orange, lemon, lime, cherry, root beer and cola. It stabilizes pulp in concentrates and finished drinks. Gum Arabic is generally preferred in citrus oil emulsion concentrates. It forms a cloud-producing agent in beverages. In dry beverage mixes where spray-dried emulsion of vegetable oil produces a stable free flowing powder which on dispersal in water gives a cloudiness or turbidity typical of citrus or other juices. Gum is also used in manufacture of beer. It maintains the beer foam under adverse conditions and is responsible for the “lace curtain” effect on the sides of the glass when the beer is consumed. It is also used for wine clarification.

Diary product

Gums have the ability to prevent crystallization of sugar; therefore, it has been used in many diary products and confectioneries. It is used as the cream stabilizer. It provide uniform, smooth creamy texture to the ice cream and maintain this texture during ice-thaw cycle.

Low calorie milk shake

Gum when used in milk shakes, suspends solids and helps emulsify the immissible fat in the system. It also control overrun and provide smooth creamy body. Gum is also used in ice pops, water ices, sherbets (etc.).

Cheese products

In the manufacture of cheese the gum speeds up coagulation, increases yield of curd solid by 10 per cent and separation and makes removal of curd easier. It also gives the finished cheese an excellent, smooth, resilient body and texture. Gum reduces the exudation of water from cheese from soft cheese such as cheese spreads and melted cheese products in which water content is high.

Instant and cooked pudding

Gum produces firm pudding in cold water system with excellent body, texture and flavour release. It stabilizes pudding system and reduces weeping.

Pie and pastry fillings

Gum acts as cold water gel base for instant bakery jellies and instant lemon pie fillings. It gives improved flavour release and a soft gel body with broad temperature tolerance.

Meat products

Gum is used in the manufacture of processed meat such as salami, bologna and sausages. It acts as a binding and stabilizing agent and retains water. In canned meat and fish products it is used as a thickener. In preparation of synthetic meat products form plant proteins, gum is used to give the eating quality of chewy protein gels to impart meat like chewiness.

Miscellaneous

Gum emulsifies and stabilizes all types of salad dressings, emulsifies oil and suspend solids in meat and flavour sauces, suspends solids and produce uniform body in fountain syrups and controls overrun, fat dispersion and prevent freeze-thaw break down in whipped toppings. Gum is used in dry powdered stable oil soluble vitamins food supplement, jellies, jams, synthetic potato chips, macaroni, spaghetti and so many other preparations.

Other uses

Gums are used for making inks, paints, metal cutting fluids, toys, air fresher gels, hydro-mulching to promote seed germination, boiler compounds, ceramics, welding rods, cleaners crayon and in mining, polymerization aide, lithography, stabilizing insecticides, surface coating of wood and plastics, polish, leather industry, adhesives and explosives.

Uses of gum resins and resins

Gum resins have been used in industry such as perfumery, and other cosmetics, medicine, spices and incense. Resins are now mainly employed in paints, varnishes, lacquers, sizing paper, manufacture of soap, linoleum, sealing wax, adhesives, medicines, ink, etc.

Improvement of Tapping Technique

Introduction of new tapping methods using ethephon (2 chloroelhyl phosphonic acid), a plant growth regulator, have increased exudation of gum/gumresin in certain plants such as Anogiessus latifolia, Acacia senegal, Commiphora wightii, Sterculia urens and Mangifera indica. These methods also ensure the sustainable yield, regeneration and survival of the tapped trees. Ethephon is safe, inexpensive and non-toxic. It is used for enhancing rubber yield in rubber tree, ripening of fruits (mango, bananas and citrus), induction of abscission, flowering, root initiation, seed germination and breaking of dormancy.

The first systematic study on improvement of resin tapping was done during World War II because of the urgent need of oleoresin. Chemical stimulation experiments on resin flow by application of sulfuric acid; hydrochloric acid and sodium hydroxide have been carried out. The prolongation of oleoresin flow by acid stimulation resulted in 50 to 100 % higher production (Snow, 1949). The oleoresin flow is also prolonged by inoculating wounds on pine trees with the suspensions of pitch canker fungus, Fusarium lateritium and F. pini (Hepting, 1947; 1954; Clapper, 1954). Ethephon (2 Chloroethylphosphonic acid) and paraquat (1,1 dimythyle 4,4' bipyridium chloride) or other herbicides when administered alone or in combination into the stem, induces extensive oleoresin soaking within the stem of pines (Roberts, 1973; Roberts et al., 1973; Barker & Schmid, 1976; Cooper, 1976; Nix, 1976; Peters & Roberts, 1976; Peters et al., 1978; Schnell & Toennisson, 1978; Kossuth et al., 1984). The treatment does not induce oleoresin soaking in Abies balsamea, Larix laricina (Kiatgrajai et al., 1976a,b) Pseudotsuga and Tsuga canadensis (Rowe et al., 1976; Conner et al., 1977). Ethephon treatment induces formation of gum cavities in the secondary xylem and cortex of cherry, peach, plum and prunes (Wilde & Edgerton, 1975).

Application of Indol 3-acetic acid (IAA) morphactin (EMD-7301) and kinetin (6-furfuryl aminopurine) increase the number of gum ducts in Sterculia urens (Setia & Shah, 1977a) but was ineffective in Commiphora wightii (Setia & Shah, 1977b). An increase in the number of vertical resin ducts due to application of growth regulator was also reported in Pinus halepensis (Fahn & Zamski, 1970). These reports however, do not mention the effect of the hormones on the amount of gum or gum resin secreted.

Application of ethephon enhances exudation of gum and gumresin in certain hardwood species (Nair et. al., 1980; 1985; Bhatt and Shah, 1985; Bhatt, 1987; Bhatt et. al., 1989; Bhatt & Mohan Ram, 1990; Nair et. al., 1995). Neem gum which contains about 35% protein (Anderson & Hendrie, 1971) has great potential for industrial use, but neem tree (Azadirachta indica) is generally not tapped because of the meager amount of exudation. Administration of ethephon and paraquat (1,1'-dimethyle 4,4' bipyridium salt) into the sapwood of neem mediated copious gum exudation (Nair et. al., 1980; 1985). The treatment induced formation of gum ducts and cavities in the sapwood (Nair et. al., 1995).

Guggul, an oleo-gumresin exuded by Commiphora wightii is the source of an important drug, the guglip, which possesses hypocholestraemic and hypolipaemic activi-ties and is used in the control of artherosclerosis, the main cause of coronary heart disease. The traditional tapping methods used are unproductive and destructive. Due to wasteful and injurious tapping techniques, the natural population of this small tree of the semi-arid regions of India has depleted fast. An improved tapping technique using "Mitchie Golledge knife coupled with ethephon application can enhance googol production by about 22 times over that obtained from control and rapid wound healing. April and May are peak months for guggul tapping as established by localization of resins using epifluorescence microscopy (Bhatt et. al., 1989).

Anogeissus latifolia occurs commonly in dry deciduous forests of India. Besides providing fuel wood and timber, the tree yields a valuable gum called gum ghatty. Gum ghatty has been used in India for calico printing, in confectionery, ceramics, food and pharmaceuticals. An improved tapping method based on application of ethephon yielded about 466 fold increase in gum (Bhatt, 1987b). Similar method is successfully tested in Mangifera indica (Bhatt & Shah, 1985).

Gum Arabic produced by Acacia senegal has various uses. Acacia senegal trees in India does not yield gum. A study by Bhatt and Mohan Ram (1990) indicated that 0.8 to 0.9 kg of good quality gum can be obtained per tree by introducing 4 ml of ethephon containing 960 mg of the active substance through a hole in the sapwood in April/May.

A dry exudate from Sterculia urens known as gum karaya is one of the least soluble gums used for many industries such as petroleum and gas, textiles, paper and pulp, pharmaceuticals medicine and several other products (Gautami & Bhat, 1992). The commercial tapping of karaya is done by blazing, peeling, or by making deep cuts at the base of the bole using an axe. These methods often lead to the death of the tapped trees. On account of crude tapping methods and over exploitation the population of karaya trees has markedly declined. In the absence of cultivation of these trees in regular plantation, there is a grave concern about the loss of wild germplasm of S. urens. Presently, the governments of Madhya Pradesh, Rajasthan, and Utter Pradesh have imposed a ban on the tapping and collection of the gum karaya to allow recovery and regeneration of this tree.

As gum karaya is vital for tribal economy and its trade value is substantial, there is a pressing need to develop a scientific and sustainable tapping method to increase the yield and ensure the survival of the tapped trees. A simple and safe technique of tapping with substantial increase in the yield is being developed using ethephon to enhance gum yield and wound healing. After 45 days a thick wound tissue has developed at the injured region and nearly replaced the damaged tissue. The wound is completely healed 60 days after tapping. The Yield has increased about 20 to 30 times more than the control. There was a marked difference in the yield among individual trees, presumably due to heterozygosity. The systematic and scientific tapping technique using ethephon as stimulating agent for gummosis or gumresinosis could ensure substantial improvement and sustainable production of these materials.

Conclusion

The future of natural gum and resin industry is uncertain and therefore, a thorough economic study of the national and international trade is necessary. Synthetic products are preferred by the industry because of the uncertain supply and cost of natural gums and resins. However, unstable oil prices, decreased production and high costs of the synthetic material create a promising future for natural gums and resins. In spite of the competition from synthetic products, natural gum and resins are preferred in certain industries as they are superior.

The tapping methods used are brutal and injurious to the plants, often leading to their death. The technology available is old and the innovations are essential for sustain-able yield and quality control. A concerted effort by researches and agencies such as research institution, Universities and non-governmental agencies is urgently needed to improve all aspects of the industry such as tapping, collection, processing, grading, classification and marketing. R and D are completely lacking in the area of utilization of natural gums and resins. The industry completely depends on traditional and certain ad hoc investigations by individuals. Research into genetic improvement and selection of species for production of gums and resins should be initiated which may lead to establishment of plantation of these species. Gum and resin industry can provide employment and a steady additional income to rural people and thereby stop their migration into the towns and cities.

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UTILISATION DURABLE DES GOMMES ET DES RÉSINES PAR UNE TECHNIQUE AMÉLIORÉE DE GEMMAGE PRATIQUÉE SUR CERTAINES ESPÈCES

M. Balakrisnan NAIR
Department of plant sciences, Peermade development society, IDUKKI, État de Kerala
Inde

RÉSUMÉ

Les gommes et les résines représentent un groupe important de produits forestiers autres que le bois. Les applications industrielles des gommes et des résines ont connu un essor considérable ces dernières années. Ces produits sont utilisés par de nombreuses industries totalement différentes: papier, textiles, pétroles, produits pharmaceutiques et cosmétiques, produits alimentaires, vernis, laques et savons. Bien qu'un grand nombre de végétaux produisent de la gomme, l'exploitation commerciale est limitée à la famille des légumineuses, des sterculiacées et des combrétacées. La gomme est également extraite de graines, d'algues et de micro-organismes. Les résines sont produites par les végétaux de la famille des pinaceae (colophane, ambre), par des légumineuses (copal), des dipterocarpaceae (dammar), des burseraceae (élémi, encens, guggul - ou myrrhe indienne) et des ombellifères (ase fétide, galbanum). Les gommes et les résines sont considérées comme des sous-produits ou des produits finals de certaines chaînes métaboliques. Des sols pauvres, la sécheresse et d'autres conditions hostiles favorisent la production de gommes et de résines, dont l'Indonésie, l'Inde, la Chine et le Soudan sont les principaux producteurs. Dans le monde entier et en particulier dans les pays en développement, des millions de personnes vivent de la récolte de gommes, de résines et de latex. Mais le marché de ces produits a reculé au cours des années pour plusieurs raisons, dont les principales sont les méthodes non scientifiques et brutales d'extraction, l'exploitation excessive conduisant à la mort de l'arbre saigné et l'offre erratique des produits sur le marché. Pour extraire les gommes et les résines à des fins commerciales, on procède par martelage, écorçage ou en pratiquant de profondes entailles sur le tronc. En raison des méthodes d'extraction dangereuses et antiéconomiques et de l'exploitation excessive, les populations de végétaux producteurs de gommes et de résines ont baissé de façon notable. Faute de cultiver ces végétaux, le risque est grand de perdre les plasmas germinatifs sauvages. Des techniques d'extraction simples et efficaces, qui garantissent un rendement optimal et la régénération des arbres exploités, ont été mises au point pour la gomme arabique (Acacia senegal), la gomme ghatti (Anogeissus latifolia), la gomme neem (Azadirachta indica), le guggul (Commiphora weightii) et la gomme karaya (Sterculia urens). Ces méthodes, qui permettent une production durable, sont exposées en détail.

Mots-clefs : Gommes, résines, produits forestiers autres que le bois, techniques d'extraction améliorées, éthéphon.