Macroalgal Phycocolloids 147
high amount from algae. All these polysaccharides are water-soluble, and can be extracted with hot water
or alkaline solutions (Minghou 1990).
Commercial hydrocolloids
Colloids are compounds that form colloidal solutions, an intermediate state between a solution and a
suspension, and are used as thickeners, gelling agents, and stabilizers for suspensions and emulsions (see
Table 1). Hydrocolloids are carbohydrates that, when dissolved in water, form viscous solutions. The
phycocolloids are hydrocolloids extracted from algae and represent a growing industry, with more than
one million tons of seaweeds extracted annually for hydrocolloid production (Ioannou and Roussis 2009;
Pereira et al. 2009a; Pereira 2010b).
Many seaweeds produce hydrocolloids, associated with the cell wall and intercellular spaces.
Members of the red algae (Rhodophyta) produce sulfated galactans (e.g., carrageenans and agars) and the
brown algae (Heterokontophyta, Phaeophyceae) produce uronates (alginates) (Pereira 2010b; Bixler and
Porse 2011; Jiao et al. 2011; Pereira and van de Velde 2011).
The various phycocolloids used in food industry as natural additives are (European codes of
phycocolloids):
Alginic acid – E400
Sodium alginate – E401
Potassium alginate – E402
Ammonium alginate – E403
Calcium alginate – E404
Propylene glycol alginate – E405
Agar – E406
Carrageenan – E407
Semi-refined carrageenan or processed Eucheuma seaweed – E407A
Sulfated galactans
The commonest and most abundant cell wall constitutes encountered to date in Rhodophyta are families
of galactans bearing the trivial names agars and carrageenans. The pioneering studies conducted in
Japan and Canada established that the backbone structure of both agars and carrageenans was based
on repeating galactose and 3,6-anhydrogalactose residues, β-(1→4) and α-(1→3) linked, respectively.
The main feature distinguishing the highly sulfated carrageenans from the less sulfated agars was
the presence of D-galactose and anhydro-D-galactose in the former and D-galactose, L-galactose, or
anhydro-L-galactose in the later. Classification of these polysaccharides based on their solubility and
gelling properties proved unsatisfactory, so attention was focused on the common underlying structural
patterns (Anderson et al. 1965; Craigie 1990). The seminal concept of the masked repeating structure first
reported for the agar-like porphyran (Anderson and Rees 1965) is now widely accepted for both agars and
carrageenans (Craigie 1990).
Agar. Agar is the phycocolloid of most ancient origin. In Japan, agar is considered to have been discovered
by Minoya Tarozaemon in 1658, and a monument is Shimizu-mura commemorates the first time it was
manufactured. Originally, and even at present times, it was made and sold as an extract in solution (hot)
or in gel form (cold), to be used promptly in areas near the factories; the product was then known as
“tokoroten”. Its industrialization as a dry and stable product started at the beginning of the 18th century,
and it has since been called “kanten”. The word “agar-agar”, however, has a Malayan origin and agar
is the most commonly accepted term, although in French- and Portuguese-speaking countries it is also
called “gelosa” (Minghou 1990; McHugh 2003).
Agar production by modern techniques of industrial freezing was initiated in California by Matsuoka
who registered patents in 1921 and 1922 in the United States. The present manufacturing method by
freezing is the classic one, and derives from the American one developed in California prior to World War
high amount from algae. All these polysaccharides are water-soluble, and can be extracted with hot water
or alkaline solutions (Minghou 1990).
Commercial hydrocolloids
Colloids are compounds that form colloidal solutions, an intermediate state between a solution and a
suspension, and are used as thickeners, gelling agents, and stabilizers for suspensions and emulsions (see
Table 1). Hydrocolloids are carbohydrates that, when dissolved in water, form viscous solutions. The
phycocolloids are hydrocolloids extracted from algae and represent a growing industry, with more than
one million tons of seaweeds extracted annually for hydrocolloid production (Ioannou and Roussis 2009;
Pereira et al. 2009a; Pereira 2010b).
Many seaweeds produce hydrocolloids, associated with the cell wall and intercellular spaces.
Members of the red algae (Rhodophyta) produce sulfated galactans (e.g., carrageenans and agars) and the
brown algae (Heterokontophyta, Phaeophyceae) produce uronates (alginates) (Pereira 2010b; Bixler and
Porse 2011; Jiao et al. 2011; Pereira and van de Velde 2011).
The various phycocolloids used in food industry as natural additives are (European codes of
phycocolloids):
Alginic acid – E400
Sodium alginate – E401
Potassium alginate – E402
Ammonium alginate – E403
Calcium alginate – E404
Propylene glycol alginate – E405
Agar – E406
Carrageenan – E407
Semi-refined carrageenan or processed Eucheuma seaweed – E407A
Sulfated galactans
The commonest and most abundant cell wall constitutes encountered to date in Rhodophyta are families
of galactans bearing the trivial names agars and carrageenans. The pioneering studies conducted in
Japan and Canada established that the backbone structure of both agars and carrageenans was based
on repeating galactose and 3,6-anhydrogalactose residues, β-(1→4) and α-(1→3) linked, respectively.
The main feature distinguishing the highly sulfated carrageenans from the less sulfated agars was
the presence of D-galactose and anhydro-D-galactose in the former and D-galactose, L-galactose, or
anhydro-L-galactose in the later. Classification of these polysaccharides based on their solubility and
gelling properties proved unsatisfactory, so attention was focused on the common underlying structural
patterns (Anderson et al. 1965; Craigie 1990). The seminal concept of the masked repeating structure first
reported for the agar-like porphyran (Anderson and Rees 1965) is now widely accepted for both agars and
carrageenans (Craigie 1990).
Agar. Agar is the phycocolloid of most ancient origin. In Japan, agar is considered to have been discovered
by Minoya Tarozaemon in 1658, and a monument is Shimizu-mura commemorates the first time it was
manufactured. Originally, and even at present times, it was made and sold as an extract in solution (hot)
or in gel form (cold), to be used promptly in areas near the factories; the product was then known as
“tokoroten”. Its industrialization as a dry and stable product started at the beginning of the 18th century,
and it has since been called “kanten”. The word “agar-agar”, however, has a Malayan origin and agar
is the most commonly accepted term, although in French- and Portuguese-speaking countries it is also
called “gelosa” (Minghou 1990; McHugh 2003).
Agar production by modern techniques of industrial freezing was initiated in California by Matsuoka
who registered patents in 1921 and 1922 in the United States. The present manufacturing method by
freezing is the classic one, and derives from the American one developed in California prior to World War