2.2. Cassava starch and flour preparations
2.2.1. Flour preparation
Cassava roots were peeled, washed and chipped to a uniform
size by a chipper, and then dried in a hot air oven at 50 C for 24 h.
Dried flour was milled by a centrifugal mill and sifted through
a 180 mm aperture sieve by a sieving machine.
2.2.2. Starch preparation
Cassava roots were peeled, washed and chipped into small
pieces by a chipper, then suspended in water, homogenized in
a blender for 2 min and filtered through a 200 mm aperture sieve.
The filtratewas allowed to settle until a dense, firm starch layerwas
deposited. The supernatant was decanted, and the starch cake was
rewashed three times. The starch cakewas dried in a hot air oven at
3. Results and discussion
3.1. Chemical composition and amylase activity
The results of analysis of chemical compositions of the flour and
starch samples are presented in Table 1 and Table 2. Cassava flours
contained protein, lipid, ash and crude fiber in ranges of 0.32e1.18,
0.10e0.72, 1.50e2.34 and 1.53e2.48 g/100 g dwb, respectively.
Starch, the main component of the flours, ranged from 80 to 86 g/
100 g dwb. These values were comparable to those reported by
Moorthy et al. (1996) (79e86 g/100 g). Flour of F-rayong2 variety
contained noticeably higher amounts of protein (1.18 g/100 g dwb),
ash (2.34 g/100 g dwb) and crude fiber (2.48 g/100 g dwb) than
others. For the starch samples, protein, lipid and fiber existed in
very small amounts (approaching zero), so they could not be
detected by the proximal analysis. Ash content in the starch
samples ranged between 0.01 and 0.19 g/100 g dwb. F-18 flour
contained the highest a-amylase activity (0.0426 CU/g flour), followed
by MF-6 (0.0135 CU/g), whereas only 0.0002e0.0020 CU/g
flour was found for the others. The differences in chemical
compositions between flour and starch may influence pasting and
gel textural properties.
Among the 12 cassava varieties, significant variations in protein,
lipid, ash, fiber and starch contents (p < 0.05) of flours were
observed. Even within the same textural group, these components
were still not consistent. Therefore, it could be said that the
differences in chemical components would be a characteristic of
each variety rather than a characteristic of each textural group.
3.2. Pasting properties
Fig. 1 shows pasting properties of representative flours and
starches determined by a RVA. There were wider variations in peak,
minimum, final viscosity and setback of flour samples than those of
starches. Starches from all cassava varieties had very similar pasting