Agar

Agar
Synonym
Agar has several synonyms: Agar-agar, Japanese-Isinglass, Vegetable gelatin.

Biological Source

It is the dried gelatinous substance obtained from Gelidiumamansii (Gelidaceae) and several other species of red algae like, Gracilaria (Gracilariaceae) and Pterocladia (Gelidaceae).

Geographical Source

Agar is produced commercially in Japan, Australia, New Zealand, the USA, and India. In India, it is produced in the Coastal regions of Bay of Bengal.

Description

Colour                         -           Depending upon the shape and the form, it is yellowish-grey or white           
to nearly Colourless.
Odour              -           Odourless
Taste               -           Mucilaginous
Shape              -           it is found in various forms like strips, sheets, flakes or Coarse
powder.
Size                 -           Sheets are 45 - 60 cm long and 10 - 15 cm wide. Bands are about
4 cm.wide, while strips are 4 mm in width. Strips are translucent,
lustrous and slender while the flakes are greyish-white in colour.

In India, the raw material being used is known as Galidiellaaccrosa and indigenous production of agar is estimated to be about 200 tones. In India, the process has been developed for the extraction of agar from the species of Hypnea.
It is insoluble in Cold water, but forms a gelatinous mass after cooling hot solution. It is soluble in boiling water and insoluble in organic solvents.







Chemical Constituents

Agar Consists of two different polysaccharides named as agarose and agaropectin. Agarose is responsible for gel strength of agar and is Composed of D-galactose and 3.6 unianhydro L-galactose units. It Contains about 3.5% Cellulose and 6% of nitrogen Containing substance. Agaropectin is responsible for the viscosity of agar solutions. It is believed to be a sulphonated polysaccharide in which galactose and uronic acid units are partly esterfied with sulphuric acid.

Uses

1.    Agar is used as an emulsifying agent and bulk laxative.

2.    It is used in the preparation of jellies, confectionery items and in microbiology, it is employed in preparation of bacteriological culture  medium

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