ABSTRACT
Microbiological and nutritional status of cassava flour was studied. Flours were produced form tubers of three cultivar of cassava TME 419 UMUCAS 37 and TMS 30572 respectively and using both traditional method and high cassava quality flour (HQCF) techniques. Microbiological assessment covered the total microbial count (bacteria and fungi) in both the fermenting legion and produced flour as well as microbial succession during fermention while nutritional assessment covered the determination of proximate composition, mineral and vitamin contents of the flours and hydrogen cyanide content. Results obtained show that the bacteria load of the fermentation water was at averages of 175.67x106 cfu/ml, 168.33 x106 cfu/ml and 189.67 x 106 cfu/ml in TME 419, UMUCAS 37 and TMS 30572 respectively on the first day but reduced to 114 x 106 cfu/ml, 109 x 106 cfu/ml and 122 x 106 cfu/ml on the second day. The fungi load rather increased from 120. 67 x 102 cfu/ml to 145.33 x 102 cfu/ml in fermenting TME 419, 109.0 x 102 to 147.102 cfu/g in fermenting TMS 30572. The bacteria flora of the fermenting cassava was similar having bacteria species which include Staphylococcus aureus, Proteus, Escherichia coli, Bacillus, Pseudomonas, Lactobacillus. Bacillus, Pseudomonas and Staphylococcus aureus were found on the second day. The fungi flora were yeast, Penicillium and Aspergillus species on the first day while Rhizopus and Fusarium were in addition found on the second day. The physiochemical characteristics of the produced flours show a pH range of 5.53 to 6.30 and temperature of 30oC to 31oC with titratable acidity level of 0.73% to 1.27% being higher in the traditional flour than in the HQCF. Nutritional quality of the cassava flour varied between the traditional flours and the HQCF. Protein content was between 1.37 and 1.44% (tradition) and 1.29 to 1.34% (HQCF) while fat content was 0.55% to 0.61% and 0.47% to 0.55%, fibre was 1.15% to 1.23% (traditional) and 1.13% to 1.18% (HQCF). Ash content was higher in a traditional cassava flour (1.25-1.4%) than in the HQCF (1.22 to 1.25%) similar variation were recorded in the moisture content and carbohydrate content. HCN was higher in the traditional flours (39.83 to 61.47mg/kg) than in the HQCF (22.20 to 36.25mg/kg) mineral were varied in both traditional cassava flour and the HQCF in which calcium was between 112.45 and 121.93mg/100g in the traditional and between 121.2 to 136mg/100g while the others magnesium, potassium, sodium, zinc and iron shows significant variation. Similar variation were recorded for vitamins which were generally higher in the traditional flour than in the HQCF. The variation were attributed to the differences in the techniques of production. The higher values of HCN obtained in the traditional cassava flour was attributed to inefficient detoxification while the low cyanide level in the HQCF was attributed to the combined different of heat and leaching following solubilization.
TABLE OF CONTENTS
Title
Page i
Certification
ii
Dedication
iii
Acknowledgements
iv
Table
of contents v
Lists
of Tables vii
Abstract
viii
CHAPTER
ONE
1.0 Introduction 1
1.1 Aim and Objective 2
CHAPTER
TWO
2.0 Literature Review 4
CHAPTER
THREE
3.0 Materials and Methods 9
3.1 Source of Material 9
3.2 Production of Traditional Cassava Flour 9
3.2.2 Production of High Quality Cassava Flour 9
3.3 Media Preparation 10
3.4 Microbiological Analysis 10
3.5 Determination of Microbial Flora 12
3.5.1 Characterization of Bacterial Isolate 12
3.5.1.1
Colony features 12
3.5.1.2 Microscopic features 13
3.5.1.3 Biochemical reaction 13
3.5.1.4 Sugar utilization test 13
3.5.2 Characterization of fungi isolates 13
3.5.2.1 Colony feature 14
3.5.2.3 Structural features 14
3.5.3 Identification of isolates 14
3.5.4 Determination of prevalence 14
3.5.5 Determination of proximate analysis 15
3.5.6 Fat content determination 15
3.5.7 Crude
protein determination 17
3.5.8 Ash
content determination 18
3.6 Determination
Physic-chemical Properties 19
3.6.1 Determination
of temperature 19
3.6.2 Determination
of pH 19
3.6.3 Determination
of T.T.A 19
3.6.4 Biochemical
tests 20
3.6.5 Catalase
test 20
3.6.6 Coagulase
test 20
3.6.7 Oxidase
test 21
3.6.8 Indole
test 21
3.6.9 Citrate
test 21
3.7 Urease
Test 22
3.8 Proximate Composition Determination 22
3.8.1 Moisture content determination 22
3.8.2 Determination of vitamin C 22
3.8.3 Determination
of thiamin (Vitamin B1) 23
3.8.4 Determination
of riboflavin (Vitamin B2) 23
3.8.5 Determination
of niacin (Vitamin B2) 23
3.9 Determination
of Mineral Content 24
3.9.1 Determination
of calcium and magnesium 24
3.9.2 Determination
of zinc 25
3.9.3 Determination
of iron 25
3.9.4
Determination of Gynogenic Cylyloside (HCN) 26
CHAPTER
FOUR
4.0 Results
28
CHAPTER
FIVE
5.0 Discussion, Conclusion and Recommendation 43
5.1 Discussion 43
5.2 Conclusion 47
5.3 Recommendation 48
References 49
LIST OF TABLES
Table Title
Page
4.1: Morphology
and biochemical identification of isolates 32
4.2: morphological
and cultural characteristics of Fungal isolates 33
4.3: Microbial
load of fermented cassava 34
4.4: Bacterial
succession in fermenting cassava 35
4.5: fungal
succession in fermenting Cassava 36
4.6: Percentage
occurrence of Bacteria during Cassava fermentation 37
4.7: Physiochemical
properties of Cassava flour
38
4.8: Proximate
analysis of Cassava flour 39
4.9: Composition
of mineral content 40
4.10 Composition
of Vitamin content 41
4.11 Composition of Cyanide content ` 42
CHAPTER ONE
1.0 INTRODUCTION
Cassava (Manihot esculenta) is a woody shrub that has South American origin
but is cultivated in many part of the world as annual crop especially in the
tropical and sub-tropical regions of the world and mainly for its edible
starchy tuberous root (Almazan, 1990). Cassava is reported to be the third
largest source of food carbohydrate in the world, and Nigeria is the world’s
largest producer of the crop, producing 19% of the total world cassava annual
output (Arendt et al., 2002). Cassava can be consumed
after direct cooking or fermented into various foods such as Garri, fufu,
chips, lafun and high quality flour.
The crop is a staple food for over 500
million people in the developing world (Collado-Fernandez, 2003). While the
starchy tuberous root are the main food source the young leaves are also
consumed particularly in Africa and is reported to be rich in protein (Defloor et al.,
1993). However useful cassava crop may be reports show that its use as food
limited by it perishability, low nutrient content and potential toxicity due
mainly to cyanogenic glycoside.
Although, there are several known cassava
varieties. They are grouped into two major groups of bitter and sweet depending
on the cyanide in them. Some authorities (Gallagher et al.,2003) believes that
consumption of cassava and its derived products which contain large amount of
HCN may be responsible for such visible manifestation like goiter and
Cretinism, tropicalataxicn Zenopathy etc. It is observed that many countries in
west Africa including Nigeria, Benin at coted’Ivorie have recognized the need
to transform cassava into derived products like cossetes, chikwanque, fufu,
garri, Attieke, tapioca etc) and these products actually have highest gain than
the fresh cassava root tubers.
Traditionally, cassava processing methods
involves soaking, sun drying and fermentation and there methods lead to reduce
of cyanide and no improvement of palatability as well as conversion into storable
forms.
In Nigeria as is the case, in many
developing countries the lack of suitable processing units and inadequacy of
cassava processing equipment are obvious (Guarda et al., 2004). Notwithstanding, the potential for cassava
processing could be a good alternative to reported food in order to diversify
food and ensure food safety (He and Hoseney, 1991). However, most traditional
processing techniques do not provide adequate precaution against microbial
contamination and for excess nutmeat loss but the advanced technology used in
high quality flows provide high level of sanitation and hygiene as well as
consideration for informed quality.
Against this background, the project was
designed to study the microbiological quality and nutrition states of cassava
flour produced from three different varieties of cassava using both traditional
and advanced methods.
1.1 AIM AND OBJECTIVE
The objective of the project is to study
the microbiological and nutritional status of cassava flour especially, the
objectives includes the following:
a. To
produce cassava flour from three different cassava cultivar using both traditional
method and high quality cassava flour techniques.
b. To
determine the microbial load (fungi and bacteria) of the produced cassava flour.
c. To
determine the proximate composition, minerals and vitamin content of the flours
as a measure of its nutrient status.
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