Macroalgal Phycocolloids 153
a source of alginate, the actual chemical structure of the alginate varies from one genus to another, and
similar variability is found in the properties of the alginate that is extracted from the seaweed. Since the
main applications of alginate are in thickening aqueous solutions and forming gels, its quality is judged
on how well it performs in these uses (McHugh 2003).
Twenty-five to 30 years ago, almost all extraction of alginates took place in Europe, USA, and Japan.
The major change in the alginates industry over the last decade has been the emergence of producers in
China in the 1980s. Initially, production was limited to low cost, low quality alginate for the internal
industrial markets produced from the locally cultivated Saccharina japonica. By the 1990s, Chinese
producers were competing in western industrial markets to sell alginates, primarily based on low cost.
A high-quality alginate forms strong gels and gives thick, aqueous solutions. A good raw material for
alginate extraction should also give a high yield of alginate. Brown seaweeds that fulfill the above
criteria are species of Ascophyllum, Durvillaea, Ecklonia, Fucus, Laminaria, Lessonia, Macrocystis, and
Sargassum. However, Sargassum, is only used when nothing else is available: its alginate is usually
borderline quality and the yield is usually low (Draget et al. 2004; Pereira 2008).
The goal of the extraction process is to obtain dry, powdered, sodium alginate. The calcium and
magnesium salts do not dissolve in water; the sodium salt conversely does. The rationale behind the
extraction of alginate from the seaweed is to convert all the alginate salts to the sodium salt, dissolve this
in water, and remove the seaweed residue by filtration (McHugh 2003).
Water-in-oil emulsions, such as mayonnaise and salad dressings, are less likely to separate into
their original oil and water phases if thickened with alginate. Sodium alginate is not useful when the
emulsion is acidic, because insoluble alginic forms acid; for these applications, propylene glycol alginate
(PGA) is used since this is stable in mild acid conditions. Alginate improves the texture, body, and sheen
of yoghurt, but PGA is also used in the stabilization of milk proteins under acidic conditions, as found
in some yoghurts. Some fruit drinks have fruit pulp added and it is preferable to keep it in suspension;
addition of sodium alginate, or PGA under acidic conditions, can prevent sedimentation of the pulp and
create foams. In chocolate milk, the cocoa can be kept in suspension by an alginate/phosphate mixture,
although in this application it faces strong competition from carrageenan (see Table 1). Small amounts of
alginate can thicken and stabilize whipped cream (Nussinovitch 1997; Onsoyen 1997).
Methods and techniques for analyzing phycocolloids
Preparation of ground seaweed samples for FTIR-ATR and FT-Raman
The seaweed samples were rinsed in distilled freshwater to eliminate salt and debris from the thallus
surface and dried to constant weight at 60ºC. The dried seaweeds were finely ground in order to render
the samples uniform. The samples do not need additional treatment for FTIR analysis. The analysis by
FT-Raman requires that these are devoid of pigmentation. The lack of pigmentation can be achieved by
sun drying (process used by collectors/producers of commercial seaweeds) or by pigment elimination
in the laboratory by the addition of acetone/methanol moisture (V/V) or by the addition of calcium
hypochlorite solution (4%, for 30 to 60s, 4ºC) (Pereira 2004, 2006).
Phycocolloid extraction
Before phycocolloid extraction, the ground dry material is rehydrated and pre-treated in acetone followed
by ethanol to eliminate the organosoluble fraction (Zinoun and Cosson 1996).
For extraction of the native phycocolloid, the seaweed samples are placed in distilled water
(50 mL/g), pH 7 at 85ºC for 3 h. For an alkaline-extraction (resembling the industrial method), the
samples are placed in a solution (150 mL/g) of NaOH (1 M) at 80–85ºC for 3–4 h (according to Pereira
and Mesquita 2004), and neutralized to pH 6–8 with HCl (0.3 M).
The solutions are hot filtered, twice, under vacuum, through cloth and glass fiber filter. The extract
is evaporated under vacuum to one-third of the initial volume. The carrageenan is precipitated by adding
the warm solution to twice its volume of ethanol (96 percent).
a source of alginate, the actual chemical structure of the alginate varies from one genus to another, and
similar variability is found in the properties of the alginate that is extracted from the seaweed. Since the
main applications of alginate are in thickening aqueous solutions and forming gels, its quality is judged
on how well it performs in these uses (McHugh 2003).
Twenty-five to 30 years ago, almost all extraction of alginates took place in Europe, USA, and Japan.
The major change in the alginates industry over the last decade has been the emergence of producers in
China in the 1980s. Initially, production was limited to low cost, low quality alginate for the internal
industrial markets produced from the locally cultivated Saccharina japonica. By the 1990s, Chinese
producers were competing in western industrial markets to sell alginates, primarily based on low cost.
A high-quality alginate forms strong gels and gives thick, aqueous solutions. A good raw material for
alginate extraction should also give a high yield of alginate. Brown seaweeds that fulfill the above
criteria are species of Ascophyllum, Durvillaea, Ecklonia, Fucus, Laminaria, Lessonia, Macrocystis, and
Sargassum. However, Sargassum, is only used when nothing else is available: its alginate is usually
borderline quality and the yield is usually low (Draget et al. 2004; Pereira 2008).
The goal of the extraction process is to obtain dry, powdered, sodium alginate. The calcium and
magnesium salts do not dissolve in water; the sodium salt conversely does. The rationale behind the
extraction of alginate from the seaweed is to convert all the alginate salts to the sodium salt, dissolve this
in water, and remove the seaweed residue by filtration (McHugh 2003).
Water-in-oil emulsions, such as mayonnaise and salad dressings, are less likely to separate into
their original oil and water phases if thickened with alginate. Sodium alginate is not useful when the
emulsion is acidic, because insoluble alginic forms acid; for these applications, propylene glycol alginate
(PGA) is used since this is stable in mild acid conditions. Alginate improves the texture, body, and sheen
of yoghurt, but PGA is also used in the stabilization of milk proteins under acidic conditions, as found
in some yoghurts. Some fruit drinks have fruit pulp added and it is preferable to keep it in suspension;
addition of sodium alginate, or PGA under acidic conditions, can prevent sedimentation of the pulp and
create foams. In chocolate milk, the cocoa can be kept in suspension by an alginate/phosphate mixture,
although in this application it faces strong competition from carrageenan (see Table 1). Small amounts of
alginate can thicken and stabilize whipped cream (Nussinovitch 1997; Onsoyen 1997).
Methods and techniques for analyzing phycocolloids
Preparation of ground seaweed samples for FTIR-ATR and FT-Raman
The seaweed samples were rinsed in distilled freshwater to eliminate salt and debris from the thallus
surface and dried to constant weight at 60ºC. The dried seaweeds were finely ground in order to render
the samples uniform. The samples do not need additional treatment for FTIR analysis. The analysis by
FT-Raman requires that these are devoid of pigmentation. The lack of pigmentation can be achieved by
sun drying (process used by collectors/producers of commercial seaweeds) or by pigment elimination
in the laboratory by the addition of acetone/methanol moisture (V/V) or by the addition of calcium
hypochlorite solution (4%, for 30 to 60s, 4ºC) (Pereira 2004, 2006).
Phycocolloid extraction
Before phycocolloid extraction, the ground dry material is rehydrated and pre-treated in acetone followed
by ethanol to eliminate the organosoluble fraction (Zinoun and Cosson 1996).
For extraction of the native phycocolloid, the seaweed samples are placed in distilled water
(50 mL/g), pH 7 at 85ºC for 3 h. For an alkaline-extraction (resembling the industrial method), the
samples are placed in a solution (150 mL/g) of NaOH (1 M) at 80–85ºC for 3–4 h (according to Pereira
and Mesquita 2004), and neutralized to pH 6–8 with HCl (0.3 M).
The solutions are hot filtered, twice, under vacuum, through cloth and glass fiber filter. The extract
is evaporated under vacuum to one-third of the initial volume. The carrageenan is precipitated by adding
the warm solution to twice its volume of ethanol (96 percent).