Effect of Solvent Extraction on the Gelatinisation Properties of Flour and Starch of Five Cassava Varieties
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(a) M4. Sample Mass 5.39 mg; DSC HR 10K min-1; range 2m cal s-1. (b) H-97. Sample Mass 11 mg; DSC HR 10K min-1; range 2 m cal s-1 (c) H-1687. Sample Mass 7.49 mg; DSC HR 10 K min -1; range 2 m cal s-1
Fig 2
Fig 2
In all varieties except H-1687, flour samples had a PIT that was 3-50C higher than the corresponding starch sample.
Solvent extraction of flour samples produce minimal changes in the viscosity profiles and PIT values obtained which may be a reflection of the low levels od sugars and fats present in these samples. It has been reported (Osman 1967) that quite high concentrations of sugars are required to elicit changes in peak viscosity.
The lower viscosity values obtained for flour can be partly attributed to the lower starch content present in the 50 g kg-1 slurries examined. It also possible that the high fibre content present in the flour samples could be exerting an effect on the values obtained. However, as there was little difference in the fibre content of the flour samples (Table 1), it was not possible to determine a clear relationship between gelatinisation profiles and fibre content.
The results of these experiments demonstrate that cassava varieties exist which contain starch with significantly different gelatinisation properties. There was no apparent relationship between the gelatinisation properties of the starch derived from the different varieties and the size and amylose content of the starch granules. Greater genetic diversity than was previously shown by Asatoka et al (1992) is therefore demonstrated. Results obtained for the solvent extracted samples indicate that fat and sugar content are not responsible for the varieties differences in starch gelatinisation properties or the lower values obtained for flour samples.
