ABSTRACT
Cassava is an important staple consumed in various forms by humans. Information on glycemic index of staple foods are required for effective nutrition awareness creation. This study was designed to determine the glycemic index of commonly consumed cassava varieties in south-east Nigeria. The study was descriptive-crossectional and experimental in design. The samples were subjected to chemical (proximate) analysis using standard procedure. Twenty apparently healthy undergraduate students (fasting blood sugar: 71.50±10.73 mg/dl) assigned to four groups consumed 50g available carbohydrate portions of test foods. Blood samples were collected in the fasting state, 1 hourly, 1½ hourly post-ingestion of the test food to determine plasma glucose concentrations, incremental area under the glucose curve, glycemic index and glycemic load. Results revealed that the moisture content was high in the two fufu varieties (52.20-53.75g/100g) while the white and pro-vitamin A garri were low in moisture (7.94-8.35g/100g). Ash content of the samples was highest in white garri (1.76 + 0.04 g/100g) followed by the pro-vit A garri (1.58 + 0.05 g/100g) and other fufu varieties (0.74-0.82g/100g). Yellow garri (1.16 + 0.04 g/100g) contained the highest fat value when compared to other samples (white garri -1.05 + 0.01 g/100g; white fufu -0.63 + 0.03 g/100g). Crude protein content of the samples ranged from 2.54 + 0.09 to 0.79 + 0.09 g/100g. Carbohydrates levels of the two garri varieties (82.96 + 0.06-84.42 + 0.07 g/100g) was higher that observed for fufu samples (43.04-44.03g/100g). Energy content of the samples ranged from 352.32-353.74kcal in white garri and 181.02-187.95 kcal in yellow fufu. 50g available carbohydrate was obtained from 59.5g, 60.27g of raw garri and 116.17 and 113.56g of fufu. The GI and GL values obtained ranged from 80.6-96.0 and 40.3-48.0 which classified them as high GI and high GL foods. Results revealed that there was an increase in the post-prandial blood glucose after administration of the test foods at 60 minutes. At 90 minutes, all blood glucose level significantly dropped in all test foods except in pro vitamin A fufu and garri. Thus the mean blood sugar concentration was 96.0 + 18.64mmol/l, 80.6 + 11.28 mmol/l, 91.2 + 14.10 mmol/l, 89.4 + 12.62 mmol/l. Therefore the introduction of pro Vitamin A biofortified cassava products to Nigeria households will assist in reducing the burden of diabetes and poor glycemic control.
TABLE OF CONTENTS
Title
Page i
Certification ii
Dedication
iii
Acknowledgements iv
Table of
Contents v
List of
Tables viii
List of
Figures ix
Abstract x
CHAPTER 1
INTRODUCTION
1.1 Background of the Study 1
1.2 Statement of Problem 4
1.3 Objectives of the Study 5
1.3.1 General objective of the Study 5
1.3.2
Specific objectives of the study 5
1.4 Significance of the Study 6
CHAPTER 2
LITERATURE REVIEW
2.1 Root Crops 8
2.2 Cassava Roots 10
2.2.1 Nutritional value of
cassava roots 11
2.2.2 Antinutrient content of cassava roots 14
2.2.2.1
Impact of processing on the anti-nutritional content of
cassava roots 16
2.2.3 Processing and utilization of cassava roots 17
2.3 Relevance of Fermented Indigenous Foods 20
2.4 Overview OF Garri 21
2.5 Overview of Fufu 24
2.6 Glycemic Index and Loads 25
2.6.1 Glycemic index and loads of some commonly consumed foods
in
Nigeria 26
2.6.2 Postprandial Blood
Glucose 28
2.6.3 Significance of low glycemic index and loads 29
CHAPTER 3
MATERIALS AND METHODS
3.1 Study Design 31
3.2 Sources of Raw Materials 31
3.3 Sample Preparation 31
3.3.1 Processing of Fufu from cassava roots 31
3.3.2 Processing of Garri from cassava roots 34
3.3.3 Processing
of melon soup 36
3.4 Methods of Analyses 39
3.4.1 Determination of
Proximate Composition of Cassava Varieties 39
3.4.1.1 Moisture content 39
3.4.1.2 Crude protein 39
3.4.1.3 Fat content 40
3.4.1.4 Ash content 41
3.4.1.5 Crude fibre content 42
3.4.1.6 Carbohydrate
content 42
3.4.1.7 Energy value 43
3.5 Determination of Glycemic Index and Load 43
3.5.1 Subject
characteristics 43
3.5.2 Inclusion and
exclusion criteria 44
3.5.2.1 Inclusion criteria 44
3.5.2.2 Exclusion criteria 44
3.5.3 Ethical approval 44
3.5.4 Test foods/samples 44
3.5.5 Study procedure 45
3.5.6
Calculation of glycemic index 46
3.5.7
Calculation of glycemic load 46
3.6 Data
Analysis 47
3.7 Statistical
Analysis 47
CHAPTER 4
RESULTS AND DISCUSSION
4.1 Proximate
Composition of the Samples 48
4.2 Classification
of Glycemic Index (GI) and Glycemic Load (GL) 51
4.3 Glucose
Response Area of Test Foods 53
CHAPTER 5
CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 55
5.2 Recommendations 55
REFERENCES 56
APPENDIX
LIST OF TABLES
Table
3.1: Recipe for processing of melon
soup 37
Table
4.1: Proximate composition of the
samples 50
Table
4.2: Classification of glycemic
index (GI) and Glycemic
Load (GL) 52
LIST OF FIGURES
Figure 3.1: Flow chart
for processing fufu 33
Figure 3.2: Flow chart
for processing garri 35
Figure 3.3: Flow chart
for processing melon soup 38
Figure 4.1: Graphical
representation of the glucose response area for
test
foods 54
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Glycemic
index and loads are physiological measure that ranks carbohydrate-containing
foods according to their blood glucose raising potential (Clar et al., 2017). Glycemic index (GI)
reveals information on the glycemic response (GR) that is likely expected when
an individual consumes the quantity of a food containing a fixed amount of
carbohydrate (usually 50 g) (Vega-López
et al., 2018). In this system,
GR refers to as the increase in blood glucose concentration as a result of
eating. This is expressed as the incremental area-under-the-blood-glucose-curve
(iAUC) over a period of two hours (Vega-López
et al., 2018). According to
Vega-López et al. (2018), GI value is
actually given as a relative GR; the GR of the food is expressed as a
percentage of the GR of a reference food (usually a glucose solution or white
bread): GI = (iAUCtest food/iAUCreference food) x 100.
Glycemic
load (GL) combines the qualitative and quantitative measures of carbohydrates
and it is the product of the GI and the amount of carbohydrates consumed (Clar et al., 2017). Madhu (2017) stated that
GL gives a fair idea of the glucose load or burden that results from the
ingestion of a carbohydrate containing meal. A high GI food can have a low GL
if the portion size consumed is small and a low GI food can have a high GL if
the serving size is big (Madhu, 2017). Assessment of glycemic loads of carbohydrate-rich
foods is a tool of nutritional guidelines for glycemic control and to reduce
the risk of diabetic complications (Abiche et
al., 2019). Various factors
affecting the glycemic index and loads of foods includes but not limited to
carbohydrate content of the food, starch composition and properties,
amylose-amylopectin ratio, gelatinization, retrogradation, dietary fibre,
sugars, insulin response, protein
content, processing techniques, particle size, fat and acidity (Eleazu, 2016).
Root
crops belong to the class of foods that mainly provide energy in human diet in
the form of carbohydrates, aside providing some micronutrients (Ogunlakin et al., 2012) and numerous desirable health benefits
like antioxidative, hypoglycemic, hypocholesterolemic, antimicrobial, and
immunomodulatory activities (Chandrasekara and Joseph-Kumar,
2016). In Africa, the total per capital consumption of root crops is 181
kg/capital, with cassava (115 kg/capital) being the most important (Sanni et
al., 2018). FAO (2012) revealed that in Nigeria, the per capita consumption
of root crops is 90 kg/capital, whereas 226 kilocalories of cassava are
consumed per person per day, and yearly per capita consumption of cassava is
about 102 kilograms (kg).
Cassava (Manihot esculenta, Crantz) is an
energy giving staple root crop in Nigeria (Onyenwoke and Simonyan, 2014) which has some inherent
characteristics which make it attractive. Firstly, it is rich in carbohydrates
especially starch and consequently has a multiplicity of end uses (Ogunyinka
and Oguntuase, 2020). Secondly, it is available all year round, making it
preferable to other seasonal crops such as grains, peas and beans (Ogunyinka
and Oguntuase, 2020). Cassava is a food
security crop with the capacity of addressing some health-related problems
(Onyenwoke and Simonyan, 2014). Cassava possesses 1.65 to 2.32 % crude
fibre (Eleazu and Eleazu, 2012), and essential micronutrients like vitamins A,
B and C, iron, zinc (Adenle et al., 2012), sodium, magnesium and calcium
(Omosuli, 2018). Ukenye et al. (2013), reported that white cassava
variety provides 2.07 to 7.92 % crude protein, 0.02 to 3.66 % lipids, 0.62 to
4.92 % crude fibre and 0.51 to 2.29 µg/g carotenoids while the yellow-fleshed
variety possess 1.20 to 3.88 µg/g carotenoids (Aniedu and Omodamiro, 2012).
Cassava can be
transformed into various food forms. Food products made from cassava roots are
classified into primary and secondary products. Garri,
fufu, starch, chips, flour, pellets are classified under primary
products due to the fact that they are obtained directly from cassava roots (Onyenwoke and Simonyan, 2014).
Further processing of these primary products results to obtaining of secondary
products which includes but not limited to glucose syrup, modified cassava starch
and noodle (Onyenwoke and Simonyan,
2014). Cassava can also be processed into chips (Kuda et al.,
2017), lafun (Anyaiwe et al.,
2018) and complementary food (Wireko-Manu
et al., 2016). This study therefore evaluate the glycemic index
and load of commonly consumed cassava varieties.
1.2 STATEMENT
OF PROBLEM
Diabetes
mellitus (DM) has shown a tremendous increase in prevalence with a demographic
transition in its epidemiology in recent years. The latest prevalence figure
published by the International Diabetes Federation (IDF) is 425 million persons
living with DM worldwide, with nearly 50 % of these undiagnosed (International
Diabetes Federation, 2017). In Nigeria, the prevalence of DM among adults aged
20 to 69 years is reported to be 1.7 % (International Diabetes Federation,
2017).
In Nigeria,
226 kilocalories of cassava are consumed per person per day, and yearly per
capita consumption of cassava is about 102 kilograms (FAO, 2012). Cassava is a
major staple that is a major staple that cannot be overlooked, hence the
solution is to know how much glucose raising potential of the various cassava
varieties available in our locality.
Processing
of food aids in improving the digestibility and palatability of foods. However,
the methods involved in the processing of foods vary widely, and the nutritive
value of food may be diminished depending on the methods employed. Cassava
being basically processed using various unit operations such as steeping,
dewatering and sieving results to loss of valuable nutrients such as
carbohydrate and fibre (Onyenwoke and
Simonyan, 2014). Besides, most cassava consumers are not aware of the
proximate composition of this valuable crop.
There are diverse varieties of
indigenous cassava staples available. They includes but not limited to TME 419,
TMS 98/0581, TMS 98/0510, TMS 98/0505, TMS 97/2205 and NR8082. Glycemic
index and load of most staple, commercial and/or imported food crops are well
documented (Mattei et al., 2015). However, the same cannot be said about
these staple indigenous
cassava varieties. With the increased consumption
of some of these cassava varieties, comes a need to know which appears to be
healthy choice in terms of blood glucose raising potentials.
There is a
rising burden from the complications of DM alongside the ever-increasing
prevalence of the disease (Uloko et al., 2012). DM is now seen as a risk
factor for amputations, cerebrovascular disease, heart-related problems, and
kidney disease in populations that were not previously known for these
challenging health problems (International Diabetes Federation, 2017).
1.3 OBJECTIVES OF THE STUDY
1.3.1 General objective of the study
The general objective of this study
was to determine the glycemic index and load of the common cassava varieties
1.3.3
Specific
objectives of the study were to:
i)
obtain
commonly consumed cassava varieties consumed in South East, Nigeria
ii)
determine
the proximate composition and energy density of the sample
iii)
produce
flours from these cassava varieties in traditional edible forms with
corresponding soups.
iv)
evaluate
the glycemic index and load of commonly consumed cassava varieties.
1.4 SIGNIFICANCE OF THE STUDY
Assessing
the glycemic index and loads of commonly consumed cassava varieties is a
cost-effective means of promoting research on the crops and as well enhancing
their consumption. The increased cassava consumption will be of economic
benefit farmers/agriculturists considering that the demand of cassava varieties
will increase.
Findings of
this research will provide information which would help individuals suffering
from health problems such as diabetes mellitus on the particular cassava
variety that will be more beneficial for their use in diverse food
formulations. This will help to keep their sugar level under control.
Data
obtained in this study will be of immense importance to healthy individuals and
also provide useful guidance for nutritionists and dietitians involved in meal
planning for diabetic patients. Besides, public health workers and health care
professionals will find outcome of this research highly valuable. More so,
findings of this study may be incorporated in Nigeria’s food composition table so that
provision of dietary guidance using such food composition database as a
reference material could be more effective.
This work
will also guide the government and policy makers in formulating enabling laws
to guide consumption of cassava in Nigeria, most especially in monitoring and
ensuring that cassava varieties with low glycemic index and loads and those
that possess high glycemic index and loads are used in formulation of foods for
individuals they are suited for.
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