Cassava Fermentation and Associated Changes in Physicochemical and Functional Properties

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VII. Antinutrient Factors

Fermentation has been found to bring about reduction in the antinutrients factors found in the fresh tubers. Phytate is an important antinutrients factor in cassava. The effect of different fermentation techniques on the phytate content has been examined in detail.108 Fermentation was found to reduce the phytate levels to a very large extent. The effect of time was also evident. Most of the phytate was lost during first 24 h of fermentation. Total loss was as high as 85%. The reduction in phytate is due to the activity of enzyme phytase naturally present in them. Processing into gari or eba resulted in higher loss of phytate than when processed into ampesi or fufu. Results also showed that oven drying was a effective as fermentation. The phytate lost due to conversion to fufu or ampesi was nearly same. Further processing of boiled tuber into fufu did not achieve further reduction in phytate. Processing into gari and then to eba seemed to be most effective for elimination of phytate ( Table 35 and 36)

Fermentation has also been found to be effective in reducing tannin, an important antinutrients factor109 in cassava (Table 37).¹¹⁰

VIII. Summary and Conclusion

Fermentation of cassava is an important processing technique practiced in Africa and Latin America. Although a number of products are available in these countries, the major ones are gari, fufu, Lafun from Africa, and polvilho azedo and pandeyuca from South America. Somehow , such fermented food products are relatively rare in Asia. Various microorganisms has been associated with the products.

Table 35 : Effect of Processing on Phytate Levels during Fermentation

Sample	Total phytate mg/g	Phytate lost due to processing mg/g	Loss as of total phytate %
Unprocessed	6.24	–	–
Meal	4.28	1.96	31.41
Tuo	1.44	4.31	67.19
Gari	0.70	5.54	88.78
Eba	0.55	5.69	91.19
Ampesi	1.96	4.28	68.59
Fufu	1.88	4.36	69.87

Adopted from Marfo.

Table 36 : Effect of Time of Fermentation on Phytate Level in Cassava

Period of Fermentation (h)	Phytate Content (mg/g)	Phytate lost (mg/g)	Loss (%)
0	6.24	–	–
24	1.16	5.08	81.41
48	0.99	5.25	84.13
72	0.95	5.34	85.58

Adopted from Marfo.

Table 37 : Tanin Levels in Cassava and Products by Different Methods of Analysis

	Butanol HCl (mg/100 g)	Vanillin HCl (mg/100 g)	Protein ppn mg/100 g	In vitro digestibility
Fresh freeze-dried cassava	17.4	33.6	5.4	6.0
Cassava chips	17.4	33.6	5.4	6.0
Cassava pellets	118.3	189.0	25.6	14.4
Farinha	58.3	27.0	29.7	6.7
Gari	28.1	71.7	27.6	7.6

Note : Mean of 2 to 4 observations (dry weight basis)
Source : Rickard et al.

In Colombia and Brazil, Starch after extraction is allowed to ferment for 20 to 30 d to provide fermented starch that is used in different food products. The process of fermentation has been found to bring about a number of changes in the biochemical characteristics of the tubers. Detoxification of cyanide has been invariably observed in almost all fermentations, although the extent of cyanide has been invariably observed in almost all fermentations, although the extent of cyanide removal may vary largely depending on the condition a and the rate of fermentation. A number of organic acids have been identified and quantified. Among them lactic acid seems to be most common to all fermentations. The components responsible for the characteristic flavor of gari have been identified and quantified. A large number of acids and esters have been detected.

The effect of fermentation on the nutrient value of the tubers has also been studied. Generally, reduction in vitamins, protein, amino acids, and minerals has been observed, but in many cases the results are contradictory and depend quite a lot on the type of fermentations and conditions used for fermentation. Although protein quantity is reduced, the protein quality is relatively unaffected, based on chemical scores and feeding trials. The loss of nutrients has been attributed to leaching out or due to utilization of the nutrients by the microorganisms. Sugar contents and sugar patterns have also been examined. Generally, sugars are lowered by the fermentations, but the rate and extent of reduction depend on the condition and type of fermentation. The fermentation affects the physicochemical and rheological properties of the starch only to a small extent. However, the functional characteristics are modified. In fact, the fermented starch possesses higher puffability, which rates it very suitable for many food applications. Another positive aspect of fermentation is that phytate, an antinutritive factor in cassava, is largely reduced during the fermentation. A similar effect on tannin has also been reported.

Thus, fermentation seems to be advantageous in reducing toxicity due to cyanide, improving functional properties of resulting starch, and imparting flavor and taste. The disadvantage of lower nutritive value can be easily overcome by the incorporation of the deficient nutrients before consumption. It can be concluded that fermentation with fortification can definitely be used to upgrade cassava as a value-added product, so that the crop can be consumed to a much larger extent.

Some aspects that have not been examined also need to be looked into. A number of other minor fermented products are available in different parts, especially in remote areas of Africa, Latin America, and South East Asia. These have to be examined for their physiochemical and nutritive values and suitable modification, if necessary, can be advocated to upgrade the products.

Acknowledgments

The authors wish to place on record their gratitute to Dr. G. T. Kurup, Director, CTCRI, Trivandrum for the facilities provided and to Dr. C. Balagopalan, Head and Dr. G. Padmaja, Sr. Scientist, Division of Crop Utilization and Biotechnology, CTCRI, for advice and encouragement. We are also indebted to Dr. Andrew Westby, Head, Root and Tuber Crop Group, NRI, UK for condescendingly allowing to scan through and copy the required reprints from his collection.