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

15. Clarity

The high clarity of starch has much relevants in food and textile applications and depends on the associative bonds between the starch molecules in the granules.

  1. Cassava starch

    Because of its weaker associative forces cassava starch has a better clarity than cereal starches. When derivatives of cassava starch were compared, the clarity of acetylated and propylated derivatives was better, though only to a small extent. The clarity was best when pyridineacetic anhydride was used for acetylation, probably due to the high DS achieved. Esterification tends to weaken the associative forces by reducing the available hydroxide groups[ 148]. In contrast, heat-moisture treatment reduced the clarity by strengthening the associative forces.

  2. Other Starches

    Dioscorea starches have almost equal clarity as cassava starch, indicating their associative forces were similar. Variation was not observed among different varieties of dioscorea, alata , D.esculenta and D.rotundata starches. Steam pressure treatment was found to decrease the clarity of D.alata and D.rotundata starches and the reduction was directly proportion to the pressure used and time of treatment. The reduction in clarity on pressure treatment can be attributed to the strengthening of associative forces [106]. The clarity of aroid starches is, as expected, poor and the values are closure to that of cereal starches. The clarity of starch pastes of ten accessions of colocasia esculenta was nearly equal [64]. Similarly no significant variation among ten different accessions of amorphophallus paeonifolius was observed [91]. The clarity of three accessions of canna edulis was found to be much higher than that of the aroid starches [66]. Generally ‘B’ starches appear have higher clarity compared to ‘A’ starches.

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