Physicochemical and Functional Properties of Tropical Tuber Starches: A Review

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1. Introduction
2. Extraction Techniques
3. Other components in Starch
4. Colour and Appearance
5. Granule Shape and Size
6. Spectral Features
7. X-Ray Diffraction Pattern
8. Molecular Weight
9. Amylose Content
10. Thermal Characteristics
11. Gelatinisation and Pasting Temperatures
12. Viscosity
13. Swelling Power
14. Solubility
15. Clarity
16. Sol stability
17. Digestibility
18. Conclusions

6. Spectral Features

The infrared spectra of starch of different of cassava similar with peaks at 3600-3200 (broad), 2800 (medium), 1660 (weak), 1480-1250 (medium) and a number of peaks between 1150 and 710 cm^-1. FTIR of the differences, in spite of their different Crystallinity and granule sizes. The Raman spectra of the tuber starches differed distinctly in their peak pattern in the region 800-200 cm^-1 (Fig. 3) [92].

The CP-MAS ¹³C NMR of the different starches showed typical pattern for the starches and three main peaks were observed. The first peak was at 101-102 ppm corresponding to C1 and appeared as a single or doublet depending on the source of the starch. The next peak appeared at 75-80 ppm corresponding to C2,3 . 5 and was a singlet. The final peak was at 64 and a singlet. The peaks were observed only if the starch granules contained 8-10% moisture. A clear correlation existed between the XRD pattern and the NMR peak pattern. Whereas the starches having pattern ‘A’ showed a doublet for C1 peak in NMR, those with ‘B’ pattern had clear singlet C1 peak (Tab 7. Fig 4). Thus the structural difference between the two types of starch is evident.

Table 7 : XRD Patterns and chemical shifts for C₁ peaks of different tuber starches.

Starch source	Nature of C1 NMR peak	XRD pattern
Cassava	Doublet	A
Colocassia	Doublet	A
Amorphophallus	Doublet	A
Pacchyrhizus	Doublet	A
Xanthosoma	Doublet	A
Arrow root	Doublet	A
D.alata	Singlet	B
D.esculenta	Singlet	B
D.rotundata	Singlet	B
Canna edulis	Singlet	B