The Effect of Fermentation Time on the Quality of Cassava Flour
Chapter One
OBJECTIVES OF THE RESEARCH
The main objective of this research is to study the effect of fermentation time on the quality characteristics of cassava flour.
The specific objectives of this research work are as follows;
- To produce cassava flour at controlled conditions of temperature, relative humidity and time.
- To monitor the fermentation time for breakdown and removal of cyanogenic compounds and cyanide.
- To determine the proximate composition, functional and pasting properties of the final products.
- To determine the sensory attributes of the products.
CHAPTER TWO
LITERATURE REVIEW
Cassava
Cassava (Manihot esculenta Crantz) is the most perishable of roots and tubers and can deteriorate within two or three days after harvesting. It is one of the most important staple food crops grown in the tropical Africa, and plays a major role in effort to alleviate the African food crisis because of its efficient production of food energy, year-round availability, tolerance to extreme stress conditions, and suitability to present farming and food system in Africa (Cardoso et al., 2005).
Taxonomy and classification of cassava
There is a wide range of cassava varieties which constitute the sweet and bitter cassava varieties. The designation of bitter and sweet varieties depends on taste that is associated with the levels of cyanogenic glucosides mainly linamarin. The bitter cassava (Manihot utilissima) has high level of hydrogen cyanide, evenly distributed through the root, which can amount up to 250mg/kg fresh root. It is easily recognized first by its green leaf-stalk and the whitish outer cortical layer of the root (Sirtunga et al., 2004). It also has a vegetation period of 12-18 months.
The sweet cassava (Manihot palmata) is known by a red leaf stalk and purplish outer cortical layer. In the sweet cassava, the hydrocyanic acid is confined to the skin and outer layer of the root. It’s vegetation period is relatively short usually between 6-9 months (Dulcer et al., 2008).
Nutritive value of cassava
Nutritionally, cassava is one of the principal sources of calorie to human diet, and contributes a nominal quantity of protein and fat. Among the minerals in the tuber, phosphorous and iron predominate with nutritionally significant amount of calcium (33mg per 100g fresh weight).
The tuber is relatively rich in vitamin C (35mg per 100g fresh weight), and contain traces of niacin, thiamine, riboflavin and vitamin A.
The protein of the cassava tuber is rich in arginine, but low in methionine, lysine, tryptophan, phenylalanine and tyrosine. As such, protein in cassava is not only low in quantity, but also poor in quality (Delange et al., 1994). Infact an unbalanced diet containing only cassava can lead to nutritional deficiency.
History and economic impact of cassava
Cassava (Manihot esculenta Crantz) originated in the Northeast Brazil and Paraguay, and was later assimilated by the West Indians (Cardoso et al., 2004). Having begun with these regions, cassava is now cultivated in all tropical regions of the world among which Nigeria is one of them.
Nigeria’s cassava production is by far the largest in the world, three times more than the production in Brazil and almost double the production in Indonesia and Thailand (FAO, 2006). In 2002, the Food and Agricultural Organization of the United Nation in Rome estimated cassava production in Nigeria to be approximately 34million tonnes which on comparison with other crops ranks first, followed by yam production 27million tonnes, sorghum 7million tonnes, millet 6million tonnes and rice 5million tonnes (FAO, 2006). In Nigeria, cassava appears to be the major staple food that matches the population growth. It is a major source of dietary energy for low-income consumers. It also plays a role in providing a stable food base in areas prone to drought and famine. Cassava is predominantly used as food with small amount in agro-allied industrial livestock feed and starch production (Sanni, 2005).
Many traditional foods are processed from cassava roots among which are; flour, dried chips, cassava flour, fufu, farinha, etc. Cassava starch is extensively utilized by most of the food industries to produce ; baked products, confectioneries, canned fruits, jam, preserves, monosodium glutamate (MSG), production of commercial caramel, glucose, dextrose, dried yeast, etc. Non-food uses of cassava starch include; corrugated cardboard, remoistening gum, wall paper industry, textile industry and wood furniture (Moorthy, 1985). Harvesting and transporting of roots from farm to homestead and subsequent processing are mainly done by women. Most of the steps in processing are carried out manually using simple and inexpensive tools and equipment that are available to small farmers. Cassava processing is labour intensive and productivity is usually very low.
Transport of products to markets is made difficult by the poor condition of rural roads.
The drudgery associated with traditional processing is enormous and the products from traditional processing methods are often contaminated with undesirable extraneous matter. Some of the products are therefore not hygienic and so are of poor market value. Better processing methods can improve the life-styles and health of rural people through higher processing efficiency, labour saving and reduced drudgery, all of which improve the quality of products.
CHAPTER THREE
MATERIALS AND METHODS
Materials
Source of raw material
The fresh bitter cassava roots (97/4779) used in the study were obtained from National Root Crop Research Institute, Umudike, Umuahia, Nigeria.
Equipment and chemicals used
All equipments and chemicals used for the study were obtained from National Root Crops Research Institute (NRCRI) Umudike and Reliable research laboratory services Umuahia, Abia State. All chemicals used were of analytical grade.
Methods
Sample preparation and fermentation
The cassava tubers were washed, drained and peeled. Working in a sterile hood, the tubers were rapidly grated into a sterile container with a sterile hand grater. Five hundred grams (500g) of the sample was weighed rapidly into small jute bags and tied with fishing line thread. They were then put in incubators set at the appropriate temperatures (30oC, 35oC and 40oC), relative humidity (65%, 75% and 85%) and allowed to ferment for the desired length of time (48hours, 72hours and 96hours).
Generation of relative humidity (RH)
The various relative humidity were generated by using the method described by Ogueke et al. (2013). These weres as follows;
- 65% RH was generated by dissolving 50g of anhydrous NaNO3in 33.3ml of water at 100o
- 75% RH was generated by dissolving 20g of NaCl in 50ml of water at 100o iii) 85% RH was generated by dissolving 25g of KCl in 50ml of water at 100oC.
The salt solutions were put in the incubators to create the required relative humidity in the environment of fermentation.
CHAPTER FOUR
RESULTS AND DISCUSSION
RESULTS
Tables 4.1 to 4.8 shows the effect of fermentation variables (temperature, relative humidity and time) on the pH, TTA and HCN of cassava mash, the proximate, functional, chemical, pasting and sensory properties of cassava flour.
CHAPTER FIVE
CONCLUSION / RECOMMENDATION
Conclusion
- The study revealed that the conditions for the fermentation of sample 4 (temperature 40oC, relative humidity 85% and time 72h) produced cassava flour with relatively high crude protein content, ash, swelling index and water absorption capacity. Statistical analysis showed that the values obtained for these parameters were significantly different (p<0.05) from the values obtained from the other samples. This still buttress the fact that sample 4 may be the best product in terms of the nutritional quality and mouldability for swallow during eating. Although it did not produce a product with the least HCN content after toasting, the value obtained (4.77mg/kg) was very low and it did not differ significantly (p>0.05) with the least HCN value (4.31mg/kg).
- However, the result of the pasting properties revealed that sample 1(fermented at 30oC, 65%RH, 72h) had the best properties for mouldability whose HCN content was found to be lower than that of sample 4, and the nutritional quality comparable to sample 4 fermented at (temperature 40oC, relative humidity 85% and time 72h).
- A critical look on the results also indicated that the length of fermentation may have had the most significant effect on most of the parameters monitored. Samples fermented for 96h had least values for HCN. The least pH values were also obtained in 96h fermented samples. Although samples fermented for 72h had the highest values in terms of protein, ash, water absorption capacity and swelling index.
- Sensory results also showed that the product was well accepted by the panelists.
Recommendation
Ø In this direction of study, other works should be carried out on the effect of other variables such as innoculation of cassava mash with preferment liquor under controlled conditions of fermentation (temperature, relative humidity and time) so as to further enhance cassava flour processing.
Contribution of work to knowledge
Researches have been conducted on the impact of seeding fermenting cassava mash with preferment liquor, effect of temperature and duration of fermentation on the quality of cassava flour. However, there is no information on the variability in the environmental and fermentation conditions (temperature, relative humidity and duration of fermentation).
Thus, the contributions of this work to knowledge are as follows;
- By varying the fermentation conditions, HCN content of these samples; sample1 fermented at (30oC, 65RH, 72h) sample2 fermented at (40oC, 65RH, 72h) sample3 fermented at (30oC, 85RH, 72h) sample4 fermented at (40oC, 85RH, 72h) sample7 fermented at (30oC, 75RH, 96h) sample8 fermented at (40oC, 75RH, 96h) sample11 fermented at (35oC, 65RH, 96h) sample12 fermented at (40oC, 85RH, 96h) reduced below the control sample which was produced using the traditional method. Ø Different fermentation conditions are required for producing cassava flour that could be used for different purposes thus, sample 1 fermented at (30oC, 65% RH, 72h) can be taken as the best suited for eba while sample 11 fermented at (35oC, 65RH, 96h) can be taken as the best for drinking.
- That varying the fermentation conditions resulted in products with improved nutritional quality.
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