Literature review
12
Chitin and chitosan possess a variety of desirable characteristics that have made them among
the most widely used biopolymers with numerous applications. These features include
biocompatibility, biodegradability, adsorption capacity, antibacterial properties, gel -forming
abilities, as well as the capacity to form films and chelate metal ions. (SHUKLA et al., 2013)
(ARANAZ et al., 2021).
6. Physicochemical properties
A- Degree of Deacetylation (DD) of Chitosan
The degree of deacetylation is generally regarded to be a key factor of the structural parameters
contributing to the physical and biological properties of chitosan. The degree of deacetylation
identifies the biopolymer as chitin or chitosan. The DD of chitosan depends mainly on the
source of the chitin and chitosan preparation process. In the case of chitosan, DD must be above
50%. (HASAN et al., 2022), The DD is an indicator of the efficiency of chemical deacetylation
and the purity of chitosan, which increases with higher DD. (HOSNEY et al., 2022).
The degree of deacetylation (DD) of chitosan can be determined using various analytical
methods, such as infrared spectroscopy, nuclear magnetic resonance spectroscopy, and
elemental analysis. In addition, other methods such as titration, viscometry, and colorimetry
also can be employed. (NURHAYATI and TANG, 2022) (AHING and WID, n.d.) (SABNIS
and BLOCK, 1997).
B- Molecular weight
The molecular weight (MW) of a polymer is an important factor that determines the str ength of
its fibre and the viscosity of the solution. In the case of chitosan, the MW is closely related to
the degree of deacetylation (DD), Studies have demonstrated that the MW of chitosan decreases
as the degree of deacetylation increases (HASAN et al., 2022).
Based on their MW, chitosan can be classified into three categories (THOMAS et al., 2020).
Table 1 : Chitosan classification based on MW :
Low-molecular weight Chitosan
MW < 50 kDa
Medium-molecular weight Chitosan
MW 50-250 kDa
High-molecular weight Chitosan
MW > 250 kDa
Several methods are used to calculate the MW of chitosan, including light scattering, gel
permeation chromatography (GPC), and capillary viscometry. Among these methods, capillary
viscometry is considered the simplest and most widely used method for determining the MW
of chitosan (THOMAS et al., 2020).
C- Viscosity
From a technological perspective, the viscosity of polymers is a critical parameter as highly
viscous solutions can be challenging to handle and process. When chitosan is dissolved in an
acidic solution, it yields a viscous solution. The viscosity of the solution is dependent on various
parameters, including the molecular weight (MW), degree of deacetylation (DD),
concentration, pH, and temperature of the chitosan solution. (ARANAZ et al., 2021)
(THOMAS et al., 2020).
12
Chitin and chitosan possess a variety of desirable characteristics that have made them among
the most widely used biopolymers with numerous applications. These features include
biocompatibility, biodegradability, adsorption capacity, antibacterial properties, gel -forming
abilities, as well as the capacity to form films and chelate metal ions. (SHUKLA et al., 2013)
(ARANAZ et al., 2021).
6. Physicochemical properties
A- Degree of Deacetylation (DD) of Chitosan
The degree of deacetylation is generally regarded to be a key factor of the structural parameters
contributing to the physical and biological properties of chitosan. The degree of deacetylation
identifies the biopolymer as chitin or chitosan. The DD of chitosan depends mainly on the
source of the chitin and chitosan preparation process. In the case of chitosan, DD must be above
50%. (HASAN et al., 2022), The DD is an indicator of the efficiency of chemical deacetylation
and the purity of chitosan, which increases with higher DD. (HOSNEY et al., 2022).
The degree of deacetylation (DD) of chitosan can be determined using various analytical
methods, such as infrared spectroscopy, nuclear magnetic resonance spectroscopy, and
elemental analysis. In addition, other methods such as titration, viscometry, and colorimetry
also can be employed. (NURHAYATI and TANG, 2022) (AHING and WID, n.d.) (SABNIS
and BLOCK, 1997).
B- Molecular weight
The molecular weight (MW) of a polymer is an important factor that determines the str ength of
its fibre and the viscosity of the solution. In the case of chitosan, the MW is closely related to
the degree of deacetylation (DD), Studies have demonstrated that the MW of chitosan decreases
as the degree of deacetylation increases (HASAN et al., 2022).
Based on their MW, chitosan can be classified into three categories (THOMAS et al., 2020).
Table 1 : Chitosan classification based on MW :
Low-molecular weight Chitosan
MW < 50 kDa
Medium-molecular weight Chitosan
MW 50-250 kDa
High-molecular weight Chitosan
MW > 250 kDa
Several methods are used to calculate the MW of chitosan, including light scattering, gel
permeation chromatography (GPC), and capillary viscometry. Among these methods, capillary
viscometry is considered the simplest and most widely used method for determining the MW
of chitosan (THOMAS et al., 2020).
C- Viscosity
From a technological perspective, the viscosity of polymers is a critical parameter as highly
viscous solutions can be challenging to handle and process. When chitosan is dissolved in an
acidic solution, it yields a viscous solution. The viscosity of the solution is dependent on various
parameters, including the molecular weight (MW), degree of deacetylation (DD),
concentration, pH, and temperature of the chitosan solution. (ARANAZ et al., 2021)
(THOMAS et al., 2020).