42
3 Chitin
These are removed by treatment with 2M hydrochloric acid for 48 h. The sample
which by now consists mainly of chitin is then further treated to remove the pigments
followed by further treatment with sodium hydroxide to remove residual proteins and
alkali-soluble glucans. Further processing could then follow to obtain chitin fibers
or powder.
This method of extraction of chitin from mushrooms has proven effective in five
different species of edible mushrooms (Ifuku et al. 2011). These include the common mushroom (Agaricus bisporus), king trumpet mushroom (Pleurotus eryngii),
maitake (Grifola frondosa), shiitake (Lentinula edodes) and buna-shimeji mushroom
(Hypsizygus marmoreus). This method yields between 1.3 and 3.5% chitin depending on the variety of mushrooms. Chitin production from edible mushrooms faces
the challenge of competing with food, especially in vegan diets where mushrooms
are used as a substitute for meat as a source of nutrients and desired meaty texture.
3.5.3 Extraction from Fish Scales
Relatively, fewer studies have gone into extraction of chitin from fish scales than
from crustacean shells. This is largely due to the lower yield of chitin in fish scales
compared to crustaceans and mollusks. Nonetheless, the extraction of chitin from
fish scales is well worth further exploring as the demand for more sources of chitinbased biopolymers rises. Furthermore unlike crustaceans such as crabs and lobsters,
fish scales are always removed before the fish is served as food. Therefore, sourcing
of fish scales for chitin production requires more sustainable logistics. Increasing
worldwide farming of tilapia, a scaly fish would also mean increasing demand for
ways to utilize the fish scales generated as waste.
The process of chitin extraction from fish scales begins with separating the scales
from the fish. This is usually done at the point of sale at the markets or prior to
processing in fish factories or cooking at restaurants. The fish scales are then collected
by the processor and washed with water at room temperature to remove fins, skins
and other residues.
The main extraction process then commences at demineralization where the minerals present within the structure of the fish scale are dissolved in a 0.5M acid solution, usually hydrochloric acid. The ratio of dried scales to acid solution is generally
between 1:10 and 1:20 ratio of grams of dry fish scales to volume of acid solution in
ml. Continuous stirring is also applied to ensure even distribution as the demineralization process progresses. A time period of 90 min to 2 h is allowed for this process.
This is then followed by washing to remove the acid filter and drying.
The next stage is then to remove the proteins, deproteinization. This is achieved
by treating the demineralized residue with 1% solution of sodium hydroxide at 50 °C
for 3 h under low stirring (~250 rpm). What remains at this point is mostly chitin with
some pigments and impurities (Boarin-Alcalde and Graciano-Fonseca 2016). Further
treatment is then carried out to remove the pigments and odor causing impurities.
This can be achieved with the addition of sodium hypochlorite or ethanol.
3 Chitin
These are removed by treatment with 2M hydrochloric acid for 48 h. The sample
which by now consists mainly of chitin is then further treated to remove the pigments
followed by further treatment with sodium hydroxide to remove residual proteins and
alkali-soluble glucans. Further processing could then follow to obtain chitin fibers
or powder.
This method of extraction of chitin from mushrooms has proven effective in five
different species of edible mushrooms (Ifuku et al. 2011). These include the common mushroom (Agaricus bisporus), king trumpet mushroom (Pleurotus eryngii),
maitake (Grifola frondosa), shiitake (Lentinula edodes) and buna-shimeji mushroom
(Hypsizygus marmoreus). This method yields between 1.3 and 3.5% chitin depending on the variety of mushrooms. Chitin production from edible mushrooms faces
the challenge of competing with food, especially in vegan diets where mushrooms
are used as a substitute for meat as a source of nutrients and desired meaty texture.
3.5.3 Extraction from Fish Scales
Relatively, fewer studies have gone into extraction of chitin from fish scales than
from crustacean shells. This is largely due to the lower yield of chitin in fish scales
compared to crustaceans and mollusks. Nonetheless, the extraction of chitin from
fish scales is well worth further exploring as the demand for more sources of chitinbased biopolymers rises. Furthermore unlike crustaceans such as crabs and lobsters,
fish scales are always removed before the fish is served as food. Therefore, sourcing
of fish scales for chitin production requires more sustainable logistics. Increasing
worldwide farming of tilapia, a scaly fish would also mean increasing demand for
ways to utilize the fish scales generated as waste.
The process of chitin extraction from fish scales begins with separating the scales
from the fish. This is usually done at the point of sale at the markets or prior to
processing in fish factories or cooking at restaurants. The fish scales are then collected
by the processor and washed with water at room temperature to remove fins, skins
and other residues.
The main extraction process then commences at demineralization where the minerals present within the structure of the fish scale are dissolved in a 0.5M acid solution, usually hydrochloric acid. The ratio of dried scales to acid solution is generally
between 1:10 and 1:20 ratio of grams of dry fish scales to volume of acid solution in
ml. Continuous stirring is also applied to ensure even distribution as the demineralization process progresses. A time period of 90 min to 2 h is allowed for this process.
This is then followed by washing to remove the acid filter and drying.
The next stage is then to remove the proteins, deproteinization. This is achieved
by treating the demineralized residue with 1% solution of sodium hydroxide at 50 °C
for 3 h under low stirring (~250 rpm). What remains at this point is mostly chitin with
some pigments and impurities (Boarin-Alcalde and Graciano-Fonseca 2016). Further
treatment is then carried out to remove the pigments and odor causing impurities.
This can be achieved with the addition of sodium hypochlorite or ethanol.