Agar is a gelatinous substance obtained from extracting red algae species found in shallow ocean waters in countries like Japan, Australia, and Korea. It has traditionally been collected and dried from bamboo structures in the ocean during summer months, but modern methods now use deep freezing. Agar is a complex heteropolysaccharide composed of agarose and agaropectin, with agarose responsible for its gelling properties. It is used as a laxative, suspending agent, emulsifier, and in various pharmaceutical products due to its gelling abilities.

1. AGAR
Synonym
Agaragar, Japanese Isinglass, Vegetable gelatin.
Botanical Source
It is the dried gelatinous substance obtained by extraction with water
from Gelidium amansii or various species of red algae
like Gracilaria and Pterocladia, belonging to family Gelidacea.
Geographical Source
Japan was the only country producing agar before the World War II, but it is now
produced in several countries like, Japan, Australia, New Zealand and other
allied species, Korea, South Africa, United States, Chile, Spain, and Portugal.
Collection
The red algae are grown in rocks in shallow water or on the bamboos by placing
them in the ocean. Collection of the algae is usually made in summer (May and
October). The bamboos are taken out and the seaweeds are stripped off. Algae are
dried, beaten with sticks and shaken to remove the sand and shell attached to them.
Then the entire material is taken to high altitude, washed with water and bleached
by keeping them in trays in the sunlight, sprinkling water and rotating them
periodically. The agar is then boiled; one part of algae with 50 parts of water
acidified with acetic acid or dilute sulphuric acid.
Modern method of deep freezing is being utilized in the preparation of agar in
recent development of technology. The algae which is collected is washed in
running water for a day and then extracted firstly with dilute acid in steam heated
digester and then with water for 30 min, the hot solution so obtained is cooled and
deep freezed in an ice machine. The water present in the agar is converted to ice
and these masses are powdered, melted and filtered in rotary vacuum filter. The
moist agar is dried using dry air and powdered agar is obtained.

2. Morphology
Chemical Constituents
Agar is a complex heterosaccharide and contains two dif-ferent polysaccharides
known as agarose and agaropectin. Agarose is neutral galactose polymer and is
responsible for the gel property of agar. It consists of D-galactose and L-galactose
unit.
Uses
Agar is used to treat chronic constipation, as a laxative, sus-pending agent, an
emulsifier, a gelating agent for suppositories, as surgical lubricant, as a tablet
excipient, disintegrant, in production of medicinal encapsulation and ointment and
as dental impression mold base.