ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...
ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ... ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...
The results of the analysis of alkaloids, oxalates, phytates, cyanogens and saponins of Amadumbe obtained from different locations are shown in Table A3-4c. Table A3-4c: The levels ofsome anti-nutritional factors in processed and nnprocessed tubers (Colocasia esculenta) from Zulnland Alkaloids Oxalates Phytates Cyanogens Saponin Esikhawini white (EW) 0.19 0.13 3.1 0.012 0.136 Boiled white (BW) 0.04 (79) 0.06 (54) 1.3 (58) 0.001 (92) 0.056 (59) Roasted white (RW) 0.04 (79) 0.14 (0) 1.1 (65) 0.003 (75) 0.079 (42) Fried white (FW) 0.13 (32) 0.14 (0) 0.8 (74) 0.002 (83) 0.123 (10) Esikhawini purple (EP) 0.18 0.10 2.8 0.025 0.145 Boiled purple (BP) 0.06 (67) 0.06 (40) 1.4 (50) 0.008 (68) 0.052 (64) Roasted purple (RP) 0.08 (56) 0.21 (0) 1.8 (36) 0.003 (88) 0.10 (31) Fried purple (FP) 0.04 (78) 0.1 (0) 0.8 (71) 0.006 (76) 0.095 (34) Mtubatuba white (MtW) 0.22 0.07 2.2 0.013 0.125 Mtubatuba purple (MtP) 0.17 0.09 3.2 0.018 0.119 Makatini white (MakW) 0.14 0.08 2.6 0.014 0.122 Makatini purple (MakP) 0.22 0.07 3.2 0.013 0.124 a Figures in parentheses indicate the percentage decrease over the values of the corresponding raw tuber There was variation in the total oxalate content ofthe corms in this study between tubers from the different localities. The highest losses of oxalate (a decrease from 0.13 mg!g to 0.06 mg/g - 54 per cent) occWTed when the white Amadumbe sample was boiled. When the samples were roasted and fried, there was an increase in oxalate content. 63
The phytate content of the Amadumbe tubers investigated is given in Table A3-4c. Phy1ate concentration ranged between 2.2 - 3.2 mg/g. Results indicated that phy1ate content was partially reduced by the cooking treatments. The phytate content of the processed tubers was reduced by up to 74 per cent. The cyanogen content ofAmadumbe tubers ranged from 12 - 2.5 mg HCN equivalent per 100 g dry weight of tubers. The results, presented in Table A3-4c, showed low variability of HCN content. The processing techniques employed were effective in substantially reducing the cyanogens to low levels (0.1 - 0.8 mg HCN equivalent/lOOg). Boiling for 30 minutes was found to be highly effective in reducing the HCN by up to 92 per cent in white and 68 per cent in purple Amadumbe. A loss ofHCN content (75 per cent in white and 88 per cent in purple Amadumbe) was also observed when the tubers were roasted for 30 minutes or fried for 15 minutes. Phytochemical screening revealed the presence of alkaloids at different concentration levels in all the unprocessed samples. A precipitate or flocculation in any ofthe samples was regarded as a positive test result for alkaloids (Figure A3-3). 64
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The results of the analysis of alkaloids, oxalates, phytates, cyanogens and saponins of<br />
Amadumbe obtained from different locations are shown in Table A3-4c.<br />
Table A3-4c: The levels ofsome anti-nutritional factors in processed and<br />
nnprocessed tubers (Colocasia esculenta) from Zulnland<br />
Alkaloids Oxalates Phytates Cyanogens Saponin<br />
Esikhawini white (EW) 0.19 0.13 3.1 0.012 0.136<br />
Boiled white (BW) 0.04 (79) 0.06 (54) 1.3 (58) 0.001 (92) 0.056 (59)<br />
Roasted white (RW) 0.04 (79) 0.14 (0) 1.1 (65) 0.003 (75) 0.079 (42)<br />
Fried white (FW) 0.13 (32) 0.14 (0) 0.8 (74) 0.002 (83) 0.123 (10)<br />
Esikhawini purple (EP) 0.18 0.10 2.8 0.025 0.145<br />
Boiled purple (BP) 0.06 (67) 0.06 (40) 1.4 (50) 0.008 (68) 0.052 (64)<br />
Roasted purple (RP) 0.08 (56) 0.21 (0) 1.8 (36) 0.003 (88) 0.10 (31)<br />
Fried purple (FP) 0.04 (78) 0.1 (0) 0.8 (71) 0.006 (76) 0.095 (34)<br />
Mtubatuba white (MtW) 0.22 0.07 2.2 0.013 0.125<br />
Mtubatuba purple (MtP) 0.17 0.09 3.2 0.018 0.119<br />
Makatini white (MakW) 0.14 0.08 2.6 0.014 0.122<br />
Makatini purple (MakP) 0.22 0.07 3.2 0.013 0.124<br />
a Figures in parentheses indicate the percentage decrease over the values of the<br />
corresponding raw tuber<br />
There was variation in the total oxalate content ofthe corms in this study between tubers<br />
from the different localities. The highest losses of oxalate (a decrease from 0.13 mg!g to<br />
0.06 mg/g - 54 per cent) occWTed when the white Amadumbe sample was boiled. When<br />
the samples were roasted and fried, there was an increase in oxalate content.<br />
63
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