Table 1.

Preparation and characterization of chitooligosaccharides (CHOSs) prepared using various methods.

Methods	Hydrolysis Conditions	Analytical Techniques	Characteristics of CHOS	References
Chemical
Hydrochloric acid	CS: 1% (w/v) HCl: 0.5 M Temperature: 65 °C; time: 36 h	Size exclusion chromatography; viscometry	MW: 73.8 kDa	[23]
	CS: 2 mg HCl: 12.07 M Temperature: 40 °C; time: 28 h	Size exclusion chromatography	DP: 1	[24]
	CS: 10 mg/mL HCl: 0.1 M Temperature: 83 °C; time: 30 h	1H NMR; viscometry	DP: 13	[25]
Hydrogen peroxide	CS: 100 mL at 1% (w/v) H2O2: 1 M Temperature: 60 °C; time: 2 h	1H NMR; 13C-NMR; gel permeation chromatography; FTIR; MALDI-TOF	MW: 1.2 kDa; DP: 3–13	[30]
	CS: 1000 mL at 1% (w/v) H2O2: 20 mL (30%, v/v) Phosphotungstic acid: 1 g Temperature: 65 °C; time: 40 min	FTIR	DP: 2–9	[31]
	CS: 10 g H2O2: 100 mL (2%, v/v) Phosphotungstic acid: 1 g Temperature: 25–28 °C; time: 24 days	1H NMR; gel permeation chromatography; XRD; FTIR	MW: 2.04 kDa	[32]
	CS: 1000 mL at 1% (w/v) H2O2: 3 mL (30%, v/v) Phosphotungstic acid: 0.04 g H2O: 17 mL Temperature: 70 °C; time: 20 min	FTIR; X-ray diffraction	MW: 4.7 kDa	[35]
Redox pair	CS: 100 mL at 1% (w/v) Ascorbic acid: 0.05 M H2O2: 0.1 M Temperature: 60 °C; time: 2 h	1H NMR; 13C-NMR; gel permeation chromatography; FTIR; MALDI-TOF	MW: 0.7 kDa; DP: 2–8	[30]
Physical
Microwave	Power: 100 W; frequency: 2.46 GHz; time: 20 min	Static light scattering; gel permeation chromatography; FTIR; 1H-NMR	MW: 30 kDa; DDA: 91% via 1H-NMR	[36]
Enzymatic
Lipase	E: 8% (w/w) of CS Temperature: 50 °C; pH: 5.0; time: 12 h	Viscometry	MW: 79 kDa	[9]
Pepsin	E/S: 1:100 (w/w) of CS; temperature: 50 °C; pH: 4.5; time: 16 h	Viscometry, FTIR, differential scanning calorimetry	DDA: 84%, Mv: 5.1 kDa	[44]
	E/S: 1:100 (w/w) of CS; temperature: 40 °C; pH: 4.5; time: 1 h	Viscometry, HPLC	DP: 16	[45]
Chitosanase	E: 1700 U/mg CS Temperature: 40 °C; pH: 5.0; time: 24 h	Gel permeation HPLC	DP: 3–7	[41]