ABSTRACT
This study evaluated the nutritional and phytochemical properties, its retention/loss in five cultivars of sweet potato flour (Umuspo3, Umuspo1, Tis87/0087, Ex-igbariam and Tis8165) as affected by unit operations (peeling, oven drying and milling). The result showed that physicochemical properties of the five cultivars were significantly (P<0.05) affected by cultivar variation and unit operations. Umuspo1 and Umuspo3 flours had the highest protein (7.63% and 6.83%), minerals (33.0% and 30.13% for phosphorus, 1.72mg/100g and 1.69mg/100g for calcium,0.39mg/100g and 0.35mg/100g, for magnesium,136.91mg/100 and 137mg/100g for sodium, 0.12 mg/100g and 0.21mg/100g for iron, 214.19mg/100g and 178.46mg/100g for potassium), flavonoids (52.27mg/100g, and 50.09mg/100g), total carotenoid (7.03mg/100g and 7.01mg/100g), beta-carotene (5.02mg/100g and 5.00mg/100g), vitamins B2 (0.49mg/100g and 0.57mg/100g), B3 (0.92mg/100g and 0.97mg/100g) and C (49.06mg/100g and 47.69mg/100 but were low in oxalate (0.02mg/100g and 0.03mg/100g), hydrogen cyanide (0.08mh/100g and 0.03mg/100g), saponin (0.01mg/100g and 0.01mg/100g), alkaloids (0.00mg/100g), phytate (0.82mg/100g and 0.83mg/100g), trypsin (5.78mg/100g and 2.08mg/100g) and phenol (0.31 and 0.51mg/100g). Tis87/0087 had the highest carbohydrate (2.68%), energy (355.80%), phytate (1.03mg/100g) and least protein (4.79%), fat (0.60%),calcium (0.64mg/100g), vitamin C (30.36mg/100g), beta-carotene (0.30mg/100g) and tannin (1.16mg/100g), Ex-igbarian was highest in vitamin B1 (5.30mg/100g), E (0.49mg/100g), trypsin (13.18mg/100g) but lowest in phosphorus (22.02mg/100g), iron (0.05mg/100g) and potassium (165.72mg/100g), Tis8164 had highest hydrogen cyanid (0.26mg/100g), oxalate (0.12mg/100g and saponin (0.05mg/100g), and lowest in total carotene (1.59mg/100g), vitamin B3 (0.35mg/100g), and vitamin C (30.36mg/100g) and magnesium (0.27mg/100g). Peeling had a significant decrease (P<0.05) on the proximate, minerals, beta-carotene and vitamin E. Oven drying significantly decreased all the parameters except potassium, flavonoids and phenol that increased. Milling showed significant decrease on, energy and fat and was not significantly affected on others. Despite the losses experienced by these cultivars during flour production in some of the physicochemical parameters analyzed, Umvspo3 and Umvspo1 had the highest values in majority of the nutrients and least values of anti- nutrients analysed, Therefore, it is recommended to use orange fleshed sweet potatoes for flour production since they retain better amount of their nutrients after processing and peeling sweet potato roots in flour production should be avoided.
TABLE OF CONTENTS
Title
page i
Declaration
ii
Certification
iii
Dedication iv
Acknowledgements v
Table
of contents vi
List
of tables xii
List
of figures xiii
List
of plates xiv
Abstract xv
CHAPTER 1: INTRODUCTION
1.1 Background of the Study 1
1.2 Statement of the Problem 3
1.3 Objective of the Study 4
1.4 Justification of the study
4
CHAPTER 2: LITERATURE REVIEW
2.1 Origin/history of Sweet Potatoes 6
2.2 Uses of Sweet Potato Especially in
Africa 7
2.3 Sweet Potato Varieties 8
2.4 Orange Fleshed Sweet Potato 9
2.5
Vitamin-A Deficiency and Orange
Fleshed Sweet Potatoes 11
2.6 Chemical and Nutritional Properties of
Sweet Potatoes 13
2.7 Phytochemicals and
Anti-nutritional Components of
Sweet Potatoes 16
2.8 Comparison of Sweet Potato with other
Staple Foods 17
2.9
Carotenoids 20
2.10
Sweet Potato Flour 21
2.11 Operational Units Involved in the Production of Sweet Potato Flour 22
2.11.1 Choosing raw material 22
2.11.2
Cleaning and trimming 22
2.11.3
Washing and brushing 23
2.11.3 Peeling 23
2.11.4
Sulphiting and blanching 23
2.11.5
Slicing 24
2.11.6
Drying 25
2.11.7
Milling and packaging 25
2.12.
Nutritional Changes of Sweet Potato
Roots during Processing 26
CHAPTER 3: MATERIALS AND METHODS
3.1
Materials 28
3.2 Production of Sweet Potato Flours 28 3.3 Proximate Analysis 30
3.3.1
Crude protein determination 30
3.3.2 Ash determination 31
3.3.3 Moisture content 31
3.3.4 Determination of carbohydrate 32
3.3.5 Determination of crude fibre 32
3.3.6
Fat content determination 33
3.3.7 Total energy 34
3.4
Determination of Minerals 34
3.4.1 Determination of phosphorus 34
3.4.2
Determination of sodium (Na) and potassium
(k) by flame photometry 35
3.4.3 Determination of iron 36
3.4.5 Determination of calcium and magnesium by
complexiometric
titrimetric method 37
3.5 Determination of Vitamins 38
3.5.1 Determination of vitamin C (Ascorbic acid) 38
3.5.2
Determination of thiamine (VIT. B1) 39
3.5.3 Determination of riboflavin (VIT B2) 39
3.5.4 Determination
of niacin content (VIT. B3) 40
3.5.6 Determination of vitamin E 41
3.5.7 Determination of total carotenoid (92074) 43
3.5.8 Determination
of β-carotene 43
3.6 Tests for
phytochemicals/anti-nutrients 44
3.6.1
Determination of hydrogen cyanide 44
3.6.2 Determination of trypsin inhibitor 45
3.6.3 Determination of tannin 46
3.6.4 Determination of alkaloid 47
3.6.5 Determination
of phytic acid 47
3.6.6 Determination of saponin 48
3.6.7 Determination of oxalate 49
3.6.8
Determination of phenol 51
3.6.9
Determination of flavonoid 52
3.7 Statistical Analysis 52
3.8 Percentage Loss and Percentage Retention 52
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Proximate
Composition of Five Cultivars of Fresh Sweet Potato Roots 54
4.1.1
Moisture content 54
4.1.2
Crude protein 59
4.1.3 Crude
fiber contents 60
4.1.4 Energy value 61
4.1.5 Fat content 63
4.1.6 Ash content 64
4.1.7 Carbohydrate content 65
4.2 Mineral Composition of Five Cultivars of
Sweet Potato Roots 67
4.2.1 Phosphorus (P) content: 68
4.2.2 Calcium (Ca) content 68
4.2.3 Magnesium (Mg) content 69
4.2.4. Sodium content (Na) 70
4.2.5 Iron (Fe) 71
4.2.6 Potassuim (k) content 72
4.3 Percentage Loss of Mineral Contents in
Five Cultivars of Sweet
Potato Flour 73
4.3.1 Percentage retention of mineral contents in
five cultivars of
sweet potato flour 76
4.4 Vitamins, Total Carotene and B-Carotene of
Five Cultivars of
Sweet Potato Roots 78
4.4.1 Total carotenoid 78
4.4.2 Beta
carotene 79
4.4.3 VitaminB1 81
4.4.4 Vitamin-B2 82
4.4.5 Vitamin B3 83
4.4.6 Vitamin C 83
4.4.7 Vitamin E 84
4.5 Percentage Loss of Total Carotenoid,
Beta-Carotene and Vitamin
Content of Five Cultivars of Sweet
Potato Roots 85
4.5.1 Percentage retention of five cultivars of
sweet potato root 91
4.6 Phytochemical/Anti-Nutritional Content of Five
Cultivars of
Sweet Potato Roots 93
4.6.1 Oxalate 93
4.6.2 Hydrogen cyanide: 95
4.6.3 Saponin 95
4.6.4 Tannin 96
4.6.5 Alkaloids 97
4.6.6 Flavonoid 98
4.6.7 Phenol 99
4.6.7 Phytate 100
4.6.8 Trypsin inhibitor (T
I) 102
4.7 Percentage Loss of
Phytochemicals and Anti-nutritional Components
of Five Sweet Potato cultivars. 104
4.8 Percentage Retention
of Phytochemicals/Anti-nutritional Components
Five Cultivars of
Sweet Potato Roots 106
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1
Conclusion 110
5.2 Recommendations 111
References 112
LIST
OF TABLES
2.1 Sweet potato chemical composition 15
(per serving of one medium 5 inch Long
Sweet Potato, 130g).
2.2 Nutritional value of raw sweet potato 100g 15
2.3:
Proximate composition of sweet potato roots and 19
other roots and tuber staples (per 100g edible)
4.1: Proximate
composition of five cultivars of fresh sweet potato root 55
4.2: Mineral composition (mg/100g) of five
cultivars of sweet potato roots 67
4.3: Percentage
loss of minerals from five cultivars of fresh sweet potato
flour 75
4.4 Percentage retention of minerals of five
cultivars of fresh sweet potato roots 77
4.5: Vitamins, total carotenoids and
beta-carotene composition (mg/100g)
of five cultivars of sweet potato
roots. 80
4.6: Percentage loss and percentage retention
of vitamins of five cultivars
of fresh sweet potato roots after
peeling, oven drying and milling. 87
4.7: Percentage retention of vitamins of five
cultivars of fresh sweet potato
roots after peeling, oven drying and milling. 90
4.8: Phytochemicals/anti- nutritional composition (mg/100g) of five
cultivars
of fresh sweet potato roots 92
4.9: Percentage (%) loss
of phytochemicals/anti- nutritional compounds of five sweet potato flour. 104
4.10: Percentage (%)
retention of phytochemicals/anti- nutritional compounds 108
LIST OF FIGURES
2.1: Unit
operations involved in the 26
production
of sweet potato chips and flour
3.1 Flow
chart for production of sweet potato flour 29
LIST OF PLATES
3. 1: Umuspo 3 56
3.2 Umuspo 1 56
3.3: Tis87/0087, 56
3:4 Ex-igbairiam 56
3.5: Tis8164 57
3.6 Umuspo 3 flour 57
3.7: Umuspo 1 flour 57
3.8: Tis87/0087 flour 57
3.9: Ex-igbairiam flour 58
3.10: Tis8164 flour 58
CHAPTER 1
INTRODUCTION
1.1
BACKGROUND OF THE STUDY
Sweet
potatoes (Ipomoea batatas (L) Lam)
belong to the botanical family Convolvulaceae (Morning Glory Family). They
are perennial crops that usually grown
annually. They grow from underground tuberous roots with trailing, twisting stems that can be as long as six meters.
Sweet potatoes provide food to most of the world’s
population, occupying the position of the seventh most important food crop in the world by the beginning of the 21st
century (Woolfe, 1992).
They
are fast in maturing, rich in nutrients and are often the first crops to be
planted after a natural disaster
to provide abundant food supply to the population (Food and Culture Encyclopedia, 2003). Sweet
potatoes’ nutritional components necessary in fulfilling
human nutritional needs include carbohydrates, fibres, carotenes, thiamine, riboflavin, niacin, potassium , calcium,
iron, vitamin A and C and high quality protein. Sweet potato primarily provides
energy in the human diets in the form of carbohydrate
(Oke and Workneh, 2013). In addition, they are also good sources of minerals such as magnesium, sodium and
phosphorus (USDA, 2009).
They
have cultivars with diiferent skin colours such as orange, purple, white, cream
and yellow etc. The orange flesh
cultivars are good sources of antioxidants, vitamins, minerals and dietary fibres. They are also rich in carotene
especially the B-carotene, vitamin
A, C, B-vitamins (B2, B3 and B6), potassium
and copper (WHO, 2002, Kosambo,2004;
Welch,2005; FAO,2007).
Orange
fleshed sweet potatoes have considerable potential to contribute to a food- based approach, to combat the problem
of vitamin A deficiency which is a serious public
health concern of the poorer sections. Thus, there is a high possibility of this
subsistence crop being accepted
as a regular diet of the consumer food chain in the era of extensive population growth and nutritional crisis
to supplement as an alternative staple
food source for the resource poor farmers (Mitra, 2012). Sweet potatoes are “staple food” because they provide the main component
of the diet for many people (Onwueme,
1987).
Like
many other foods, roots and tubers are hardly consumed in their fresh state. They usually undergo some form of processing
and cooking before eating. These methods
make them safe for human consumption, extend shelf life and improve variety of products which are more convenient to
prepare, cook and consume than the raw
sweet potato (Woolfe, 1999; Stephen et
al., 2005). The tuber can be boiled, baked,
or fried. As a raw material, it is extensively used in the textile and paper industries as starch; in the confectionary
and baking industries as flour; and in the production
of syrups etc. Sweet potato flour holds moisture well, brings a richness of flavor and adds a slight sweetness to
any baked goods. The flour can be used for a wide
range of products examples include breads, cookies, muffins, pancakes, cakes, doughnuts and as thickeners. It can be combined
with other cereals or proteinous crops
to produce weaning foods for babies (Woolfe, 1992; www.culinary
collective.com, 2016).
Sweet
potato flour processing involves peeling, washing, slicing, drying and milling and there are nutrient losses during
some of these unit operations (Lyimo et
al., 2010).
So
far, little information has been reported on nutrient content of sweet potato
flour varieties as affected by
processing in Nigeria. Hence, this work proposes to study the nutrient retention/loss of flour from five
cultivars of fresh sweet potatoes as affected by
various unit operations.
1.2 STATEMENT
OF THE PROBLEM
Sweet
potatoes cannot be stored for very long temperatures below 130C and
they develop injury at temperature below
100C. Sweet potatoes like most roots and tubers lose large percentage of their
nutritional composition when undergoing processing (Ihekoronye and Ngoddy, 1985).
In
many developing countries like Nigeria, food processing operations have been a major problem which results to
decline in nutritional composition of food stuff. Processing of sweet potato roots into flour involves various unit
operations (peeling, washing, slicing,
drying and milling).
According
to Lyimo et al. (2010) it is shown
that nutrients are affected by processing methods
used and that loss of nutrients during processing depends on varieties, since some varieties are tolerant to certain
processing methods than others. Lin et al.
(2000) also reported that physicochemical
properties of sweet potatoes significantly differ among varieties. Therefore, suitable varieties for each processed
product are needed.
1.3 OBJECTIVES
OF THE STUDY
1.3.1 General objective of the study
The
general objective of this research was to determine the nutrient retention/loss
(proximate, vitamins, minerals, total
carotenoid and beta-carotene) from flour of five cultivars of fresh sweet potatoes as affected by various unit
operations (peeling, oven drying and
milling).
1.3.2 Specific objective of the study
The
specific objectives of this research were to:
i.
determine the initial components of the
parameters before unit operations
ii.
produce flour from five cultivars of sweet
potato roots (two orange fleshed, two white fleshed and one cream fleshed
cultivars).
iii.
evaluate the changes in their compositions
during the production of flour (emphasis will be on the critical control points
as Peeling drying and milling).
iv.
compare the total carotenoid and beta- carotene
content of the five cultivars of sweet potato.
v.
determine the variety of sweet potato flour
with maximum and minimum level of nutrients and phytochemicals retention during
production.
1.4 JUSTIFICATION
OF THE STUDY
Orange-fleshed
sweet potato is now emerging as an important member of the tropical tuber crops having great possibility for
adoption as regular diet of the consumer food chain
to tackle the problem of vitamin A deficiency (Mitra et al., 2012).
Sweet
potato flour is a powder made from ground sweet potato that is commonly used in baking. It can be used as a thickener and
it can also add flavor and texture to foods like
cakes, bread and cookies (Wise, 2006).
Hagenimana
et al. (1992) reported that addition
of orange-fleshed sweet potato flour in
chapattis greatly increased the total carotenoid content and various proportions
of the sweet potato flour can be used
with wheat flour to improve nutritive values in terms of fibre and carotenoids. However, lack of adequate post-harvest
processing or unit operations (FAO,
2005; CIP, 2009) can lead to loss of nutrients in sweet potato.
Sweet potato has come under scientific focus
and experts have tried to cultivate the plant
through selective breeding to produce different types of sweet potatoes called cultivars. The cultivars of a sweet potato
have different names and colours. Therefore the
evaluation of the effect of the unit operations on the physicochemical contents
(especially at the critical control
points like peeling, drying and milling) in the production of sweet potato flour will help the processor to
know the best variety of sweet
potato which has minimal nutrient losses during processing and will also guide the processor on areas to watch out in
terms of nutrient loss.
The
result of this research may be useful to consumers who want to eat foods
derived from sweet potato flesh,
underdeveloped and developing countries facing malnutrition
(especially vitamin A) especially in pregnant women and children and in processing industries who are concerned with
quality with regards to the composition as
it goes through the processing chain as well as solving food security issues.
Click “DOWNLOAD NOW” below to get the complete Projects
FOR QUICK HELP CHAT WITH US NOW!
+(234) 0814 780 1594
Login To Comment