Table 1.

Characteristic absorption bands of protein and polysaccharides.

Component	Wave Number ν (cm−1)	Type of Vibration
Gelatin	3400–3300	Stretching vibrations of NH groups (amide A)
	1700–1600	Stretching vibrations of CO– and CN– groups (amide I)
	1575–1480	Deformation vibrations of NH– groups and stretching vibrations of CN groups (amide II)
	1300–1230	Stretching vibrations of CN groups (amide III)
Sodium alginate	3600–3200	Stretching vibration of OH groups
	1580–1620	Asymmetric stretches of COO groups
	1400–1420	Symmetric stretches of COO groups
	1300–1320	Stretching vibration of CO groups
	1070–1090	Mannuronic units
	1025–1035	Guluronic units
	815–820	α-configuration of guluronic units
k-carrageenan	3600–3200	Stretching vibration of OH groups
	1270–1230	Vibration of the sulfate group
	1100–1080	Glycosidic bonds
	1070, 928–933	3,6-anhydridegalactose group
	840–850	D-galactose-4-sulfate group
Chitosan	3600–3200	Stretching vibrations of NH groups and OH groups
	2960–2880	Symmetric and asymmetric stretches of CH groups
	1670-1620	Stretching vibrations of CO groups (amide I)
	1325-1320	Stretching vibrations of CN groups (amide III)