removed from the chitin structure through heat treatment with a solution of 40%
sodium hydroxide. Creating 100% pure chitosan is no easy feat: all chemical
reactions entail side reactions, and what is typically referred to as chitosan is a form
in which around 70% or more of acetyl groups have been removed from chitin
(Kim and Rajapakse 2005).
To produce chitosan in its purest form, the concentration of sodium hydroxide
solution is increased and the temperature is raised to around 100 °C with a slightly
increased reaction time. This may result in the chitosan’s viscosity decreasing,
ultimately reducing the size of molecules. For this reason, the production process
may differ slightly depending on the purpose of chitosan use. When producing
chitin, one should take care to apply treatment as soon as the shrimp or crab shell
emerges, as it tends to decompose readily. Decomposition sets in when the shell is
left for even one day, and the shell should be dried immediately unless treatment is
being applied immediately. The use of decomposed raw materials will degrade the
quality of the chitin or chitosan (Kim 2010).
In addition to increasing production costs, drying results in slight reduction in
molecular weight. It is therefore advisable in both quality and production terms to
apply immediate and continuous treatment to a fresh shell. Since chitin is stable
with respect to bases, a good way to prevent decomposition is to treat fresh crab
shell as quickly as possible with a basic solution.
B. Producing Oligosaccharides with Physiological Functions
As mentioned previously, physiological functions are often exhibited more in the
products of chitosan once degraded into suitable sizes than in chitosan itself. Such
products include oligosaccharides, series of ten or so monosaccharides produced
from the breakdown of chitin and chitosan. Oligosaccharides have been shown to
be highly effective in fighting cancer, while their slightly sweet flavor makes them
more palatable than chitin or chitosan on their own, and they exhibit strong
absorption rates in the body (Fig. 8.29 (c)). Approaches to oligosaccharide production include the chemical method, or the use of strong hydrochloric acid to
break down molecules, and the biological method, which uses enzymes
(Kim and Rajapakse 2005).
In South Korea, the marketing of oligosaccharides produced from chitosan
broken down with hydrochloric acid has been the source of some controversy. The
use of hydrochloric acid to break down chitin and chitosan results in the production
of some harmful byproducts. Also, failure to completely remove the hydrochloric
acid can result in it entering the body and having serious effects on sugar metabolism. This can reportedly result in diabetes occurring due to problems in insulin
functioning.
For this reason, the South Korean Ministry of Health and Welfare’s Food
Standards Codex permits only the use of chitin and chitosan oligosaccharides
produced with enzymes. Because the enzymes capable of degrading chitin and
chitosan are so expensive and show such low rates of activity, their batch use in
industrial production of chitin- and chitosan-based oligosaccharides presents a large
8.4 Functional Food Materials
279
sodium hydroxide. Creating 100% pure chitosan is no easy feat: all chemical
reactions entail side reactions, and what is typically referred to as chitosan is a form
in which around 70% or more of acetyl groups have been removed from chitin
(Kim and Rajapakse 2005).
To produce chitosan in its purest form, the concentration of sodium hydroxide
solution is increased and the temperature is raised to around 100 °C with a slightly
increased reaction time. This may result in the chitosan’s viscosity decreasing,
ultimately reducing the size of molecules. For this reason, the production process
may differ slightly depending on the purpose of chitosan use. When producing
chitin, one should take care to apply treatment as soon as the shrimp or crab shell
emerges, as it tends to decompose readily. Decomposition sets in when the shell is
left for even one day, and the shell should be dried immediately unless treatment is
being applied immediately. The use of decomposed raw materials will degrade the
quality of the chitin or chitosan (Kim 2010).
In addition to increasing production costs, drying results in slight reduction in
molecular weight. It is therefore advisable in both quality and production terms to
apply immediate and continuous treatment to a fresh shell. Since chitin is stable
with respect to bases, a good way to prevent decomposition is to treat fresh crab
shell as quickly as possible with a basic solution.
B. Producing Oligosaccharides with Physiological Functions
As mentioned previously, physiological functions are often exhibited more in the
products of chitosan once degraded into suitable sizes than in chitosan itself. Such
products include oligosaccharides, series of ten or so monosaccharides produced
from the breakdown of chitin and chitosan. Oligosaccharides have been shown to
be highly effective in fighting cancer, while their slightly sweet flavor makes them
more palatable than chitin or chitosan on their own, and they exhibit strong
absorption rates in the body (Fig. 8.29 (c)). Approaches to oligosaccharide production include the chemical method, or the use of strong hydrochloric acid to
break down molecules, and the biological method, which uses enzymes
(Kim and Rajapakse 2005).
In South Korea, the marketing of oligosaccharides produced from chitosan
broken down with hydrochloric acid has been the source of some controversy. The
use of hydrochloric acid to break down chitin and chitosan results in the production
of some harmful byproducts. Also, failure to completely remove the hydrochloric
acid can result in it entering the body and having serious effects on sugar metabolism. This can reportedly result in diabetes occurring due to problems in insulin
functioning.
For this reason, the South Korean Ministry of Health and Welfare’s Food
Standards Codex permits only the use of chitin and chitosan oligosaccharides
produced with enzymes. Because the enzymes capable of degrading chitin and
chitosan are so expensive and show such low rates of activity, their batch use in
industrial production of chitin- and chitosan-based oligosaccharides presents a large
8.4 Functional Food Materials
279