TOPIC: LAC CULTURE
SUBMITTED TO: DR. MUBASHAR HUSSAIN
SUBMITTED BY: SABEEKA ZAFAR,MARYAM NASEER,HIRA SHHAID
ROLL NO: 17130814-042,043,045
UNIVERSITY OF GUJRAT
(HAFIZ HAYAT CAMPUS)
Introduction to Lac culture :
The word lac is derived from the Sanskrit word laksh which represents the number 100,000. It was used for both the lac insect and the scarlet resinous secretion it produces. Lac is a natural biodegradable, non-toxic odourless tasteless, hard resin and noninjurious to health. Lac is in fact a resinous protective secretion of tiny lac insect Kerria lacca which belongs to the family Tachardidae in the super family Coccoidea of the order Hemiptera.
The lac insect is a pest on a number of plants both wild as well as cultivated. The tiny red coloured larvae of lac insect settle on the young succulent shoots of the host plants in myriads and secrete a thick resinous fluid which covers their bodies. The secretions from the insects form a hard continuous encrustation over the twigs.
In order to obtain lac the lac insects are cultured and the technique is called lac-culture. It involves proper care of host plants, regular pruning of host plants, propagation, collection and processing of lac.
Cultivation begins when a farmer gets a stick (broodlac) that contains eggs ready to hatch and ties it to the tree to be infested. Thousands of lac insects colonize the branches of the host trees and secrete the resinous pigment. The coated branches of the host trees are cut and harvested as sticklac.
Common lac insect:
The harvested sticklac is crushed and sieved to remove impurities. The sieved material is then repeatedly washed to remove insect parts and other soluble material. The resulting product is known as seedlac. The prefix seed refers to its pellet shape. Seedlac which still contains 3–5% impurities is processed into shellac by heat treatment or solvent extraction. Lac production is found in Bangladesh, Myanmar, Thailand, Laos, Vietnam, parts of China and Mexico.
LAC AND ITS FORMS
Stick lac : The lac encrustations is separated by knife or broken off with finger from the twig of host plants and is known is stick lace or crude lac or raw lac.
Seed lac : The stick lac after grinding and washing is called seed lac.
Shellac : The manufactured product prepared from stick lac after washing and melting which takes the form of yellow coloured flakes, is called shellac.
Button lac : After melting process, lac is dropped on a zinc sheet and allowed to spread out into round discs of about 3 diameter and ¼ thickness is called button lack.
Garnet lac : It is prepared form inferior seed lac or kiri by the solvent extraction process. It is dark in colour and comparatively free from wax.
Bleached lac: It is a refined product obtained by chemical treatment. It is prepared by dissolving shellac or seed lac in Sodium carbonate solution, bleaching the solution with Sodium hypochlorite and precipitating the resin with sulphuric acid. Bleached lac deteriorates quickly and should be used within 2-3 months of manufacture.
COMPOSITION OF LAC:
The major constituents of stick lac or crude lac are resin, sugar, protein, soluble salt, coloring matter wax, volatile oils, sand, woody matters and insect bodies. The resin is always associated with an odoriferous principle, a wax and a mixture of three dyes. Removal of both wax and dye results in a marvelous colourless and transparent resin having all the characteristic properties of the resin. Chemical analysis has revealed that the resin is made of at least six major chemical components of different molecular complexities.
The building blocks of lac are mainly hydroxyaliphatic and sequiterpenic acids which are present in the proportion of 50:50. The basic blocks are however aleuritic and jalaric acids. The former is 9, 10, 16 – trihydroxy palmitic acid and the later adihydroxymonocarboxylic sesquiterpenic acid having an aldehyde function.
Composition of stick lac:
Lac resin – 68% Lac wax – 6% Lac dye – 1% Others – 25%
Importance of lac culture :
Importance of Lac Cultivation for Conservation of Biodiversity:
Lac farming provided a sure source of income. Over and above that, Lac insects also play a prominent role in the conservation of biodiversity. Lac insects are able to thrive on a wide range of eco-system.
The Lac eco-system is a complex multi-trophic web of flora and fauna. Though Lac insects are preferably harvested on Ber, Kusum and Palas; but they are able to grow quite well on more than 400 species of trees. This leads to the maintenance of diverse variety of plants having varied medicinal economic and social significance.
The richness of biodiversity involved in this farming can be judged from the abundance of 22 species of Lac predators with some 30 and 45 species of primary and secondary parasites,accompanied with many fungi, all surviving together without any clash. Lac farming also helps in the maintenance of other trees which are not directly involved in insect cultivation thus increasing the diversity of the tree fauna on one hand, and proliferation of soil microorganisms on the other.
The species of Paratachardina produce a hard and horny material which is insoluble in alcohol. As they are uni-voltine, meaning having one brood of generation in a year, they were considered as parasites in case of farming economically important commodities like tea and sandalwood15. But recent research has shown that this Paratachardina species plays a vital role in bio-suppression of weed growth without the application of any pesticides.
The commonly observed strain Kerria lacca also plays an important role in maintaining biodiversity. Kerria lacca is further divided into two sub-strains: Kusumi and Rangeeni on the basis of their host preference, life cycle and the quality of Lac secreted. The Kusumi strain, as its name suggests, specifically prefers Kusum as the host tree and its life cycle is bi-voltine: two generations equal duration in a year with a superior quality of resin that is produced.
In case of Rangeeni, their life cycle is uni-voltine, with a lower grade of resin produced. Dyes obtained from Lac insects are not toxic hence they are also incorporated in the manufacture of skin creams, food and drug manufacturing.
Uses of lac:
Because of its unique combination of properties lac finds a wide variety of application in paint, electrical automobile cosmetic adhesive leather wood finishing and other industries. Earlier about half of the total output was consumed in gramophone industry.
Lac has long been in use both for decorative and lacquers of various kinds and insulating varnishes. It is usually used as a first coating on wood to fill the pores and also applied to seal knots likely to exude resin and disfigure or spoil finished paint work.
Lac is used in manufacture of glazed paper, printing and water proofing inks, lac bangles, dry mounting tissue paper dental plates and optical frames. It is also used as a coat for metal ware to prevent tarnishing and for finishing various products such as playing cards, oil cloth and linoleum and for preserving archeological and zoological specimen.
In electrical industry lac is used as coating of insulator, coating of spark plugs, cement of sockets of electrical lamp, antitracking insulating etc.
In Pharmaceutical industry, lac is used in coating of tablets, micro-encapsulation of vitamins and coating of medicines. Lac dye is used in dying of wool and silk soft drink formulation pill coating confectionary and chocolate coating. Lac wax has wide variety of uses in manufacturing shoe polishes tailor’s chalk, lipstick, crayons.
Now a days it is also used in fruit coating.
Textbook of Applied Zoology by Pradiip V.Jabde ( page :334-339)
Introduction to lac and lac culture by Dr.Sailesh Chattopadhyay ,may 2011. (page 4-10)