3.5 Extraction of Chitin
41
will determine the extraction time and required condition. The order of demineralization and deproteinization can also be reversed according to the dominant component
in the shells. If the protein content is predominant, then the deproteinization can be
carried out before the demineralization; however if the mineral content is higher,
then the demineralization process can proceed the deproteinization for improved
efficiency of chitin extraction (Kalut 2008). The efficiency of the extraction process
is also affected by the level of contacting between the solid mass and the chemicals
being used for extraction. This can be improved by particle size reduction through
pulverization.
The quality of chitin is significantly affected by the type of acid used, temperature
and the pH. Isolation of the chitin from the dissolved minerals and proteins is achieved
by physical separation by either filtering or centrifugation. It is therefore important
that the chitin does not dissolve in the alkali or acid solution. Chitin is insoluble;
however, it becomes soluble when deacetylated into chitosan such that some of the
chitin may be lost during extraction, if not all. High temperature and high pH may
also result in the depolymerization and hydrolysis of chitin which diminishes the
physical properties, and this is undesirable. Care must therefore be taken to use the
right operating parameters that retain the chemical structure and integrity of the chitin
(Gadgey and Bahekar 2017).
3.5.2 Extraction from Mushrooms
Mushrooms are a species of fungus which form fleshy fruity bodies. They are used in
food and for medicinal applications. They grow in soil, on standing or fallen trees or in
their food source and comprise a stem and a cap with gills. Although not exclusively
aquatic in nature, mushrooms grow naturally near moisture-rich areas such as rain
forests (Ficket et al. 2017). Chitin is present in the cell wall of mushrooms where it
is embedded within the alkali-soluble beta-1,3 glucans. It plays a structural role in
cell wall of fungi.
The morphology of mushrooms varies from that of fish scales and crustacean
shells due to the fact that mushrooms contain glucans alongside proteins and chitin,
thus requiring a slightly different extraction method. The process begins with the
fresh mushrooms being crushed to reduce the particle sizes. This can be done in a
domestic blender or food processor. This is then followed by filtering and washing
in distilled water. The process of washing in water is the first extraction step which
removes the water-soluble parts of the mushroom cell wall, and these are the glucans
and the minerals. This also shows how some of the nutrients in the food are lost
during washing, although in this case it is desirable. The next step is treating with
2% w/v sodium hydroxide for 24 h at a temperature of 100 °C. This deproteinization
stage is similar to that used for crustaceans and fish scales. It is used here not just to
remove proteins but also to remove alkali-soluble glucans. The residue left behind
after separation is then repeatedly washed with distilled water until it is neutral.
What now remains after removal of the glucans and proteins is the residual minerals.
41
will determine the extraction time and required condition. The order of demineralization and deproteinization can also be reversed according to the dominant component
in the shells. If the protein content is predominant, then the deproteinization can be
carried out before the demineralization; however if the mineral content is higher,
then the demineralization process can proceed the deproteinization for improved
efficiency of chitin extraction (Kalut 2008). The efficiency of the extraction process
is also affected by the level of contacting between the solid mass and the chemicals
being used for extraction. This can be improved by particle size reduction through
pulverization.
The quality of chitin is significantly affected by the type of acid used, temperature
and the pH. Isolation of the chitin from the dissolved minerals and proteins is achieved
by physical separation by either filtering or centrifugation. It is therefore important
that the chitin does not dissolve in the alkali or acid solution. Chitin is insoluble;
however, it becomes soluble when deacetylated into chitosan such that some of the
chitin may be lost during extraction, if not all. High temperature and high pH may
also result in the depolymerization and hydrolysis of chitin which diminishes the
physical properties, and this is undesirable. Care must therefore be taken to use the
right operating parameters that retain the chemical structure and integrity of the chitin
(Gadgey and Bahekar 2017).
3.5.2 Extraction from Mushrooms
Mushrooms are a species of fungus which form fleshy fruity bodies. They are used in
food and for medicinal applications. They grow in soil, on standing or fallen trees or in
their food source and comprise a stem and a cap with gills. Although not exclusively
aquatic in nature, mushrooms grow naturally near moisture-rich areas such as rain
forests (Ficket et al. 2017). Chitin is present in the cell wall of mushrooms where it
is embedded within the alkali-soluble beta-1,3 glucans. It plays a structural role in
cell wall of fungi.
The morphology of mushrooms varies from that of fish scales and crustacean
shells due to the fact that mushrooms contain glucans alongside proteins and chitin,
thus requiring a slightly different extraction method. The process begins with the
fresh mushrooms being crushed to reduce the particle sizes. This can be done in a
domestic blender or food processor. This is then followed by filtering and washing
in distilled water. The process of washing in water is the first extraction step which
removes the water-soluble parts of the mushroom cell wall, and these are the glucans
and the minerals. This also shows how some of the nutrients in the food are lost
during washing, although in this case it is desirable. The next step is treating with
2% w/v sodium hydroxide for 24 h at a temperature of 100 °C. This deproteinization
stage is similar to that used for crustaceans and fish scales. It is used here not just to
remove proteins but also to remove alkali-soluble glucans. The residue left behind
after separation is then repeatedly washed with distilled water until it is neutral.
What now remains after removal of the glucans and proteins is the residual minerals.