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7 Agar
Global production of agar is estimated at 10,600 tonnes annually with the major
producing countries in the Asia-Pacific regions (Rhein-Knudsen et al. 2015). Agar
has well-established large-scale production process technology, and several companies across the world are involved in agar production. Examples of such companies
are MSC in Korea and Huey Shyang Seaweed Industrial Company in China. The
species of the genus Gracilaria remain the most preferred source for commercial agar
production.
In this chapter, we discuss the environmental and economic impact of agar as an
aquatic biopolymer. In doing so, we look at the red algae as a source, the occurrence
of red algae in nature and the process of extracting agar from red algae and the impact
of these processes on the environment. A review of the chemistry of agar and how it
relates to its rheological properties explain how agar differs from other polymers. The
applications of agar in several products are also explored to give an understanding of
the commercial value and the versatility of agar. Some of the progress and limitations
of commercialization of agar are also explored.
7.2 Occurrence in Nature
Agar has been in use as far back as 1658 in Japan (Armisen and Gaiatas 2009). It
occurs naturally in cell wall and within the intracellular spaces of red algae, mainly
those belonging to the genus Gracilaria, Gelidium and Gelidiella (Rhein-Knudsen
et al. 2015). These include species such as Gracilaria tikvahiae (Rocha et al. 2019).
Gelidium sesquipedale (Martinez-Sanz et al. 2019), Pterocladia, Ancatkopeltis and
Ceramium genera (BeMiller 2019; Sudha et al. 2014), Gracilaria cliftonii (Kumar
and Fotedar 2009), Gracilaria asiatica (Li et al. 2008) and Gracilaria lemaneiformis
(Li et al. 2008). Algae which serve as a source of agar are referred to as agarophytes
(Armisen and Gaiatas 2009).
Red algae species belonging to other genera are also explored for agar extraction
such as the Pyropia yezoensis (Sasuga et al. 2017) which, although more commonly
used for food as nori, is also a source of agar. The rhodophytes can be found growing
in marine, brackish and less commonly some freshwater. Although conditions of
the sea can be replicated in artificial growth environments for cultivation of these
algae as biomass source for production of agar, certain species grow naturally in
several regions across the world. For example, the Gracilaria tikvahiae is endemic
to Western North Atlantic region of the USA (Rocha et al. 2019), while the Gracilaria
lemaneiformis grows in China along the coast of Liaodong Peninsula (Li et al. 2008).
They are cultivated in ponds and estuaries and also occur naturally in larger water
bodies.
7 Agar
Global production of agar is estimated at 10,600 tonnes annually with the major
producing countries in the Asia-Pacific regions (Rhein-Knudsen et al. 2015). Agar
has well-established large-scale production process technology, and several companies across the world are involved in agar production. Examples of such companies
are MSC in Korea and Huey Shyang Seaweed Industrial Company in China. The
species of the genus Gracilaria remain the most preferred source for commercial agar
production.
In this chapter, we discuss the environmental and economic impact of agar as an
aquatic biopolymer. In doing so, we look at the red algae as a source, the occurrence
of red algae in nature and the process of extracting agar from red algae and the impact
of these processes on the environment. A review of the chemistry of agar and how it
relates to its rheological properties explain how agar differs from other polymers. The
applications of agar in several products are also explored to give an understanding of
the commercial value and the versatility of agar. Some of the progress and limitations
of commercialization of agar are also explored.
7.2 Occurrence in Nature
Agar has been in use as far back as 1658 in Japan (Armisen and Gaiatas 2009). It
occurs naturally in cell wall and within the intracellular spaces of red algae, mainly
those belonging to the genus Gracilaria, Gelidium and Gelidiella (Rhein-Knudsen
et al. 2015). These include species such as Gracilaria tikvahiae (Rocha et al. 2019).
Gelidium sesquipedale (Martinez-Sanz et al. 2019), Pterocladia, Ancatkopeltis and
Ceramium genera (BeMiller 2019; Sudha et al. 2014), Gracilaria cliftonii (Kumar
and Fotedar 2009), Gracilaria asiatica (Li et al. 2008) and Gracilaria lemaneiformis
(Li et al. 2008). Algae which serve as a source of agar are referred to as agarophytes
(Armisen and Gaiatas 2009).
Red algae species belonging to other genera are also explored for agar extraction
such as the Pyropia yezoensis (Sasuga et al. 2017) which, although more commonly
used for food as nori, is also a source of agar. The rhodophytes can be found growing
in marine, brackish and less commonly some freshwater. Although conditions of
the sea can be replicated in artificial growth environments for cultivation of these
algae as biomass source for production of agar, certain species grow naturally in
several regions across the world. For example, the Gracilaria tikvahiae is endemic
to Western North Atlantic region of the USA (Rocha et al. 2019), while the Gracilaria
lemaneiformis grows in China along the coast of Liaodong Peninsula (Li et al. 2008).
They are cultivated in ponds and estuaries and also occur naturally in larger water
bodies.