9.3.12.3 Effects of Spice Concentration on Polyphenols Content, Flavonoids Content and ABTS+ Free Radical Scavenging of Oxisoup
D. glomerata and X. parviflora were shown to exhibit higher content in flavonoids and phenolic compounds as compared to S. zenkeri and taro flour, which was poor in these compounds (Table 9.3.4). A correlation was established between the measured parameters using the spearman correlation. The results revealed that the total polyphenols correlated positively with the total flavonoids (r = 0.94; p < 0.001), while the ABTS scavenging activity correlated positively and significantly with the polyphenols (r = 0.97; p < 0.001) and flavonoids (r = 0.94; p < 0.001) levels.
Table 9.3.4 Antioxidant properties of individual ingredients that composed Oxisoup
Ingredients | Total polyphenols (g/100g) | Flavonoids(mg/100g) | ABTS(mg/100g)
Dichrostachys glomerata | 7.21 ± 0.07a | 61.71 ± 0.00a | 549.4 ± 2.3bc
Xylopia parviflora | 5.64±0.14b | 58.10 ± 0.02b | 514.0±4.6d
Scorodophloeus zenkeri | 0.28 ± 0.01j | 9.65 ± 0.01j | 2.7 ± 1.0e
farine de taro | 0.09 ± 0.01j | 6.37 ± 0.03k | 2.2 ± 0.5e
Means ± standard deviation, n = 3. Means on the same row followed by different letters in superscripts are significantly different at p < 0.05.
Because of the high linear correlation coefficient between the polyphenols and flavonoids, only the effect of the levels of spices on the flavonoids and ABTS+ free radical scavenging of Oxisoup was determined. In fact, flavonoids are one of the largest and important groups of phenolic compounds in foods (Arif et al., 2010). The surface plots showing the effect of spice levels on the flavonoid content of Oxisoup are presented in Figure 9.3.5. The greater effect of D. glomerata as compared to X. parviflora and S. zenkeri can easily be seen in the graph. The increase in the level of D. glomerata induced a significant increase in the flavonoid content of Oxisoup.
Figure 9.3.5 Typical surface plot for the effect of [D. glomerata] vs [X. parviflora] (a) and [S. zenkeri] (b) on flavonoids content of Oxisoup.
The significant effect of D. glomerata and X. parviflora on the polyphenols and flavonoids may be due to higher levels of flavonoids and polyphenols in these ingredients as compared to taro and S. zenkeri. Table 9.3.4 equally reveals that both spices D. glomerata and X. parviflora exhibit higher ABTS scavenging activity confirming the above observation, which showed that radical scavenging activity is an antioxidant mechanism devoted in general to polyphenols, and in particular to flavonoids. ABTS+ free radical scavenging is the ability of an antioxidant to provide hydrogen atoms to free radicals and to stop the chain reaction of lipid auto oxidation. As expected, ABTS+ free radical scavenging of Oxisoup changed rapidly with the change in D. glomerata, while the effect of X. parviflora and S. zenkeri were marginal.
Optimization The optimization was performed for maximization of all responses in the given range of the ingredients. The optimum level of the spices were found to be 2.66 g/L for D. glomerata, 1.43 g/L for X parviflora and 1.06 g/L for S. zenkeri, whereas total polyphenols, flavanoids, ABTS radical scavenging activity, flavor and general acceptability were 2.80 g/100 g DM, 29.6 mg/100 g DM, 760 mg/100g, 5.96 and 5.83, respectively (Table 9.3.5).
Table 9.3.5 Predicted optimum level of spices for use in the preparation of Oxisoup
Parameters | Optimum Counts
[D. glomerata] (g/L) | 2.66
[X. parviflora] (g/L) | 1.43
[S.zenkeri] (g/L) | 1.06
Taro powder can be used in the preparation of a soup with a greater acceptability, when used with 20 g instant taro powder, in 1 liter of boiled water followed by 2.66 g/L for D. glomerata, 1.43 g/L for X. parviflora and 1.06 g/L for S. zenkeri.
9.3.13 Conclusion and Future Aspects
With the successive escalation of food prices in the world, which makes food security an emergency situation, coupled to the rapid growth of population world-wide and low income food deficit in many countries, taro can play a very vital role in achieving food security. Taro has a huge potential as a base for the manufacture of convenience foods. Taro can find applications as a food ingredient in noodles, extruded paste products, baby foods, taro flour, etc. Efforts should be done to continuously generate interest for industrial production for some products, while for others improvements of existing technologies and further value addition definitely would make the products more attractive to consumers. Some of the taro products are already produced on the commercial scale, but expansion world-wide needs further effort.
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