Adulteration

The important adulterants of tragacanth gum are the Indian gum (karaya or kadaya), a product of Coplospermum gossypium, gum kuteera from Sterculia urens, powdered acacia, dextrin, and wheat and corn starch.

Agar-Agar (English, Malay and Cingalese), Red sea weed, China grass, Japanese Isinglass, Vegetable (Vegan) gelatin, Ceylon mass or Jaffna moss,

Biological Source

Geographical Source

sea to form supports on which they develop.

1. Drying of algae: After collection, the algae are dried in the sun.

2. Alkalinisation: After drying, the algae are placed in a container with very hot water in which an alkali (like caustic soda) has been poured.

3. Washing and bleaching: The algae are washed with cold water to remove all the impurities. Then, sulphuric acid is added to dealkalinise the algae and sodium hypochlorite for bleaching it. Finally, the algae are cleaned with cold water.

7. Pressing and drying: After gelling, the product is compacted by a press and dried with hot air.

The first step is preservation through dehydration, to avoid fermentation which destroys the agar and then the seaweed. The second step is pressing the weed with a hydraulic press in bales (about 60 kg) to reduce the volume. The time for collection of the algae is summer and autumn when the bleaching and drying can take place, but the final preparation of agar-agar is carried out in winter from November to February. The seaweed after collection is spread out on the shore until bleached, and then dried; it is afterwards boiled in water and the mucilaginous solution strained, the filtrate being allowed to harden, and then it is dried in the sun. During the months of May to October these poles are taken ashore and the algae is scrapped off. The algae thus obtained is dried and shaken to remove sand and shells. The dried seaweeds are washed with water to remove salt and dried again by exposing to sun (to reduce the moisture content to about 20%) which also helps in bleaching. They are then boiled with acidified water for 5–6 hours and the mucilaginous decoction is strained through cloth while still hot. On cooling, a jelly is produced, which is cut into bars, these being afterwards forced through wire netting to form strips. The moisture is removed by freezing and drying at about 35°C. The Japanese variety is derived from several kinds of algae and comes into European commerce in two forms: (1) In transparent pieces 2 feet long, the thickness of a straw, prepared in Singapore by treating it in hot water. (2) In yellowish white masses about 1 inch wide and 1 foot long. The latter is the form considered the more suitable for the culture of bacteria.

agar. Thus, the method of agar manufacture was accidentally discovered. The production of agar by the technique of industrial freezing was initiated in California in 1921 by Matsuoka. The present method of manufacture of agar by freezing is a classic one that was developed in California by H. H. Selby and C. K. Tseng prior to World War II. The shortage of agar during World War II acted as an incentive for its preparation from the coastal resources of the species of Gelidium. Payen (1859) described and referred to it as gelose. Robert Koch (1882) was the first to utilise agar in microbiology during his attempts to obtain axenic cultures of Mycobacterium tuberculosis. It was Walter Hesse, a country doctor from Saxony who introduced Koch to the powerful gelling agent when he first succeeded in using the agar as the culture medium in cultivating gelatin, which has become a universal component of the solid culture media for the cultivation of the microbes later. The doctor had learnt about agar from his wife, Fanny Hesse, nee Eilshemius. Robert Koch developed the use of agar as a medium for bacterial cultures on the advice of Angelina Fannie, his assistant, who noticed that the jellies and puddings did not melt in the hot summer weather when they contained agar.

It is used in the preparation of jellies and confectionary items. It is also a very good culture medium for the cultivation of microbes (bacteria and fungi) for bacteriological investigation. It is used as a solidifying agent in desserts, soups, sauces, etc. In the past century, this has found extensive use as a solid substrate in the culture media for microbiological work. As a vegetarian gelatin substitute it is used as a thickener in soups, jellies, ice creams, Japanese desserts like anmitsu, as a clarifying agent in brewing and for paper sizing fabrics. In the form of a gel, agarose medium is porous and can be used to measure microbe motility and mobility. Agarose can also be used for electrophoretic separation in agarose gel electrophoresis and column-based gel filtration chromatography. Research grade agar is used extensively in plant biology for seedling germination in Petri dishes under sterile conditions supplemented with a nutrient and vitamin mixture. Agar is eaten in Japan as a natural gelatin counterpart. It can also be used to make jellies, puddings, desserts, cakes and custards. Japanese cuisine, anmitsu, Indian cuisine, China grass, Burmese cuisine, kyauk and a popular Japanese food, mizuyokan, are all made from agar. It is used to prepare salt bridges used in electrochemistry. As a substitute for sand and a soy rice of nutrition, agar is used in the preparation of formicariums. In humans, agar promotes fecal bulk and influences the absorption of the dietary minerals, proteins and fat. In animals, agar decreases the protein digestion and reduces the retention of nitrogen. Agar sometimes is used as an adulterant