Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
Our intention in this chapter is to give a state-of-the-art review of the structure–function
relationships of chitosans as polysaccharides, and not to discuss how
a certain physical property is utilized in a food product. Derivatives of chitin and
chitosan are not covered, and those interested in this part are referred to a recent
review article. 2 Functional properties such as water uptake, solubility parameters,
stability, ion-binding properties, film forming, and antimicrobial properties are examples
relevant for the use of chitin and chitosans in food applications. In addition,
the application of chitosans in food for human consumption involve regulatory
approval, although chitin and chitosan can generally be recognized as safe based on
their traditional uses in different national food products; for example, in unpeeled
shrimp products and the traditional Norwegian “old cheese” (“gamalost”), the yeast
Mucor mucedo, which contains chitosan in the cell wall, is used in the fermentation
process. Chitosan is currently used only in Asia only in human food applications.
However, a number of patents describe the use of chitosan in food applications,
some of which are listed in Table 14.1.
TABLE 14.1
Food Applications of Chitosan in Patent Literature
Diet sauces
Adsorption of triglycerides/cholesterol
Alcoholic beverages
Food preservation
Solution for cooking rice
Health-care enzymatic chitosan food
Structure-forming agent
CO2-permeable packing films
Chitosan particle drink
Chitosan-stabilized peanut butter
Source: From Sandford, P.A., Advances in Chitin Sciences, Vårum,
K.M., Domard, A., and Smidsrød, O., Eds., NTNU Trondheim,
Trondheim, 6, 35, 2003. With permission.
14.2 COMPOSITION AND MOLECULAR MASS
14.2.1 CHEMICAL STRUCTURE
Chitin is a linear polymer of (1Æ4)-linked 2-acetamido-2-deoxy-b-D-glucopyranose
(GlcNAc; A-unit), which is insoluble in aqueous solvents. Chitin shares many structural
similarities with cellulose, such as conformation of the monomers and diequatorial
glycosidic linkages. Chitosans may be considered as a family of linear binary
copolymers of (1Æ4)-linked A-units and 2-amino-2-deoxy-b-D-glucopyranose
(GlcN; D-unit) (Figure 14.1). The term chitosan does not refer to a uniquely defined
compound; it merely refers to polysaccharides having different composition of Aand
D-units. It has been proposed to define chitin and chitosan based on their
solubility in aqueous acetic acid, that is, chitosan as soluble and chitin as insoluble