ABSTRACT
Orange fleshed sweet potato (OFSP) is a good source of carotenoid which can be used in Africa to combat a widespread of Vitamin A Deficiency in children. Hence, this study seeks to evaluate how different cooking methods used in the production of puree from Orange Fleshed Sweet Potato affects the chemical and sensory properties of the puree. The experimental design of this study involves 1 variety (Umuspo 1), 2 cooking methods;(boiling and steaming) and 2 treatments (peeled and unpeeled), the control being the raw sample making it a total of 5 samples. The proximate and sensory properties of the samples were analyzed. All data collected in this experiment were subjected to Analysis of Variance (ANOVA). The means were separated using Duncan Multiple Range Test (DMRT). The cooking methods used had significant effect on the proximate properties of puree samples. Puree samples that were cooked (boiling and steam) before peeling had higher nutrients (crude protein, fat, crude fibre, ash and carotenoid content) than those peeled before cooking (boiling and steam). This study revealed that the total carotenoid content of the sample were significantly different (p<0.05) and ranged from 65.61μg/g (Peeled Boiled) to 92.10μg/g (Raw). Peeling method caused significant differences (P<0.5) in the proximate properties of the samples. The sensory qualities of the OFSP purees varied significantly with the cooking methods with peeled before boiling samples having the highest acceptance. The study of puree from OFSP Variety (Var. Umuspo1) as affected by cooking methods has demonstrated that total carotenoid content was higher in unpeeled steamed samples and least in peeled boiled samples. However, based on the findings of this research work, steaming before peeling OFSP sample is a better cooking method in terms of nutrient retention compared to peeling before boiling sample.
TABLE
OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of Contents vi
List of Tables vii
List of Figures viii
List of Plates
ix
Abstract xii
CHAPTER
1: INTRODUCTION
1.1 Background of the Study 1
1.2
Statement of Problem 4
1.3 Justification of the Study 6
1.4 Objectives
of this Study 6
CHAPTER
2: LITERATURE REVIEW
2.1 Sweet Potato 8
2.1.1 Origin and distribution of
sweet potato 8
2.1.2 Botany of sweet potato 9
2.1.3 Global situation of sweet potato 10
2.1.4 Nutrient content of sweet
potato 11
2.1.5 Sweet potato value addition
and its importance 14
2.1.6 Utilization of sweet potato
and its products 16
2.1.7 Challenges associated with
the use of sweet potato 17
2.1.8 Processing techniques of
foods 19
2.1.9 Processing of sweet potato
into different products 20
2.2 Factors that Influence
Nutrient Content of Sweet Potato 20
2.3 Carotenoids 21
2.4 Factors Affecting
Degradation of Βeta-Carotene 22
2.5 Effect
of Cooking Methods on Βeta-Carotene Content of Sweet Potato 24
2.6 Effect of Cooking Methods on the
Proximate Properties of Sweet Potato 26
2.7 Sweet
PotatoPuree 27
2.7.1 Sweet potatoes purees processing 27
2.7.2 Packaging
and preservation of sweet potato purees 28
2.7.3 Quality
and rheology of sweet potato purees 29
2.7.4 Utilization
of sweet potato purees in processed foods 30
2.8 Sensory Quality
31
2.8.1 Perception
31
CHAPTER
3: MATERIALS AND METHODS
3.1 Collection
of Materials 33
3.2 Preparation
of Sample 34
3.2.1 Preparation of peeled steamed orange fleshed sweet potato puree samples 35
3.2.2 Preparation of unpeeled steamed orange fleshed sweet potato puree sample 36
3.2.3
Preparation of peeled boiled orange fleshed sweet potato puree samples 37
3.2.4
Preparation of unpeeled boiled orange fleshed sweet potato puree samples 38
3.3 Determination of Proximate Composition 39
3.3.1 Determination of moisture content 39
3.3.2 Ash content determination 39
3.3.3 Crude fibre determination 40
3.3.4 Fat determination 41
3.3.5 Crude protein determination 41
3.3.6 Carbohydrate determination 42
3.4 Determination of Total Carotenoid 43
3.4.1 Carotenoid determination 43
3.5 Sensory Evaluation 44
3.6 Experimental Design 45
3.7 Statistical Analysis 45
CHAPTER 4: RESULTS AND DISCUSSION
46
4.1 Proximate
Properties
46
4.1.1 Moisture content
47
4.1.2 Crude protein content 47
4.1.3 Fat content 48
4.1.4 Crude fibre content 49
4.1.5 Ash content
49
4.1.6 Carbohydrate content
49
4.2 Total
Carotenoid Content
53
4.3 Sensory Evaluation 56
CHAPTER 5:
CONCLUSIONAND
RECOMMENDATIONS 63
5.1 Conclusions
63
5.2 Recommendations 63
References 64
Appendices 76
LIST
OF TABLES
4.1:
Effect of cooking method on the proximate composition of Orange Fleshed Sweet
Potato Puree 51
4.2:
Effect of peeling on the proximate composition of orange fleshed sweet potato
puree 52
4.3:
Effect of cooking method on the total
carotenoid content of orange fleshed sweet potato puree 54
4.4:
Effect of peeling on the total carotenoid content of orange fleshed sweet
potato
puree
55
4.5:
Effect of cooking method on the sensory properties of orange fleshed sweet potato
puree 58
4.6: Effect of peeling on the sensory properties of orange fleshed
sweet potato puree 59
LIST OF FIGURES
2.1: Factors
leading to beta carotene degradation
23
3.1: Flow chart for preparation of peeled steamed orange fleshed sweet
potato puree samples. 35
3.2:
Flow chart for preparation of unpeeled steamed
orange fleshed sweet potato puree samples. 36
3.3: Flow chart for preparation of peeled boiled orange fleshed sweet
potato puree samples. 37
3.4:
Flow chart for preparation of unpeeled boiled
orange fleshed sweet potato puree Samples. 38
LIST OF PLATES
1:
Orange fleshed sweet potato variety (Var.
umuspo 1 (king J) 33
2: V1ps
(umuspo 1- peeled steamed) sample 60
3: V1ups(umuspo
1- unpeeled steamed) sample 60
4: V1pb
(Umuspo 1- peeled boiled) s ample 61
5: V1upb
(umuspo 1- unpeeled boiled) sample 61
6: V1r
(umuspo 1- peeled raw) sample 62
CHAPTER
1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Sweet Potato (Ipomoea batatas (L.) Lam) originated more than 5000 years ago in
South America or Central America (Rosse et
al., 2001). In the Sub-Saharan African (SSA) Nigeria is among the prime cultivators
of sweet potato with annual production estimated to be around 3.46 million tons
per year (FAO, 2008).
Orange fleshed sweet potato is a biofortified seasonal crop that is
perishable and cannot be stored for a long period of time unless preserved
adequately. Orange fleshed sweet potato (OFSP) varieties which are rich in
ß-carotene (precursor for Vitamin A) are now being used in Africa to combat a
widespread of Vitamin A Deficiency in 250,000 – 500,000 children (Low et al., 2007). Approximately two-thirds
of the children diagnosed with Xerophthalmia, as a result of lack of vitamin A,
die nearly a year after losing their sight (Aguayo and Baker 2005).The approach
of improving the consumption of orange fleshed sweet potato helps alleviate
vitamin A deficiency in Nigeria in which about 30 percent of children under the
age of six are scourged by the deficiency of vitamin A (Anderson et al., 2007; Egbe, 2012).
Orange fleshed
sweet potatoes are enrich with vitamins, minerals, dietary fiber and
antioxidants, for instance phenolic acids, anthocyanins, tocopherol and
β-carotene. They are good source of vitamin-A, vitamin-C, B-vitamins (B2, B3,
and B6), potassium and copper (FAO, 2007; Kosambo, 2004; Welch, 2005; WHO,
2002). Several nutritious food products can be produced from the nutritionally endowed
orange fleshed sweet potato (ADA, 2002; Coronel et al., 2005). It has been indicated that breads, chips, cookies,
purees, alcoholic and non-alcoholic beverage can be produced from OFSP with or
without the addition of flavour with fruit juices and spices (Dansby and
Boyell, 2003, Mills et al., 2003;
Ridley et al., 2005; Telcioglu and
Kayacier, 2007; Wireko, 2010).
There is
occurrence of changes on the nutritional makeup of sweet potato roots during
preparation and processing. Similarly,
during product development, processing may induce modification of its
nutritional, physico-chemical and organoleptic properties (Akhtar et al., 2010; Chun and Yoo, 2006;
Coronel, 2005; Leksrisompong et al. 2011;
Salvador and Fiszman, 2004; Serrat, 2004). Cooking process may lessen vitamins
(β-carotene, Vitamin C) and Minerals (Zn, Ca, Fe, P, Mn) of sweet potato as a
result of degradation and leaching (Avula and Guha, 2007). The extent of loss
depends on the cooking method used, temperature and time. Though, the positive
advantage of cooking is that it progresses digestibility and accessibility of
nutrients and promotes tastiness and shelf-life of the food (Avula and Guha,
2007; Grabowski et al., 2008).
Orange fleshed sweet potato asides serving as a
source of energy and nutrients, sweet potato flour can enhance natural
sweetness, color and flavor of processed food products. It can also be utilized
as a substitute for wheat flour to lower (bakery) expenses and as such
reduction in importation of wheat flour, and as an alternative market outlet
for those marketing the roots as raw material as well as improve the nutrient
content. Each cooking methods results in different changes in the quality
features of sweet potato (Takenaka, 2006).
In
recognition of Orange Fleshed Sweet Potatoes’ nutrition value, it is sweeter
than most varieties of white and yellow fleshed varieties and is especially
desired by children. There is concern involving its susceptibility to rotting.
In some cases, orange fleshed sweet potato varieties mature early and have low
in-ground storability making them predominantly susceptible to rotting, pest
damage and drought.
Sweet potato puree (or mash) is a
ground, pressed, blended or sieved to the consistency of a soft creamy paste or
thick liquid (Larousse, 2000). Purees normally must be cooked, either before or
after grinding, in order to improve flavor and texture, remove toxic
substances, and/or reduce their water content. Pureeing of sweet potato is performed
to improve the transformation of the roots into value-added products. Through
processing, production and home utilization, the puree is often heated. Sweet
Potato Puree is easy to prepare, but more difficult to store once made. It
often requires a processor to have a refrigerator or freezer or alternatively,
to store the fresh roots and prepare when needed.
The major
consideration in making this choice is purely economic. One must also consider
access to electricity, in many areas of rural Africa this is not available,
meaning that whatever product you select must be able to be made with an
alternative electricity source and still give quality products. It takes 1.25
kgs of fresh roots to produce kilogram of sweet potato puree. In most
Sub-Saharan African countries with sweet potato yields ranging from 5-15
tons/ha on farmer’s fields, sweet potato puree makes economic sense. Processing
technologies have been invented worldwide to transform sweet potatoes into the purees
form that can be utilized in several food products.
Process procedures for pounding of sweet
potatoes involve washing, peeling,
hand-trimming, cutting, steamed blanching or cooking, and grinding into purees
which can be canned or frozen for preservation. Finish-cooked puree can be
packaged in cans and retorted to produce shelf-stable product. The puree could
be packed in plastic containers for refrigeration or frozen storage (Perez-Dfaz
et al., 2008).
Sweet potato purees are naturally viscous and thicker
than other processed purees from other commodities such as carrots and tomatoes.
Sweet potato purees display shear thinning behavior with a yield stress, as
most of fruit and vegetable purees. Sweet potato puree has been utilized as a
constituent in numerous food products, as well as baby food, puddings, casseroles,
pies, cakes, bread, ice cream, yogurt, patties and soups (Yasufumi and Shigeki,
2000). However, the most effective commercial application of sweet potato puree
is for baby food.
Utilization of the sweet potato principally
controls the varieties to grow, either as food directly or as processed forms, as
component of feed or as sources of industrial starch. For utilization as food, a
variety preference likewise tends to vary amongst and even within countries
(Carpena, 2009). Orange fleshed sweet potato varieties could be promoted for
their food security, nutritional value and for their potentials in generating income
(Padmaja, 2009).
1.2
STATEMENT OF PROBLEM
There are phenomenal
changes on the nutritional value of sweet potato roots while undergoing preparation
and processing. Correspondingly, processing during product development may induce
alterations of organoleptic, nutritional and physico-chemical properties (Akhtar
et al., 2010; Chun and Yoo, 2006;
Coronel, 2005; Leksrisompong et al.,
2011; Salvador and Fiszman, 2004; Serrat, 2004). Cooking process may decrease
vitamins (β-carotene, vitamin C) and minerals (Ca, P, Zn, Fe, Mn) of sweet
potato as a result of degradation and leaching (Avula and Guha, 2007). The
degree of loss depends on the method of cooking, temperature and time. However,
cooking has a positive advantage because it improves digestibility and
availability of nutrients, it also promotes palatability and shelf-life of the
food (Avula and Guha, 2007; Grabowski et
al., 2008).
The utilization of orange fleshed
sweet potatoes frequently involves processing of the roots into purees which
could be afterwards frozen, canned or packed in aseptic conditions to yield
shelf-stable products for all year-round product availability. The processing
of Orange Fleshed Sweet Potato is gradually becoming a welcome development for
the food industry. Most people tend to consume Orange Fleshed Sweet Potato
majorly for its carbohydrate value, thereby, engage in various methods of
processing; such as boiling, frying, baking, steaming, roasting and drying,
hence tending to disregard pureeing, which is also an important processed form
for Orange Fleshed Sweet Potato. This in turn affects its overall acceptability
and utilization of the Orange Fleshed Sweet Potato by the teaming populace.
Therefore, it is pertinent to process the Orange Fleshed Sweet Potato into
storable product forms to add value to the crop in order to contribute
significantly to food security, nutrition, income generation and enhanced livelihoods
for the common man (Ndunguru, 2003) and in addition create an avenue to study
more about the numerous food properties of the crop when processed in puree
form.
Hence, the evaluation of how different
cooking methods used in the manufacture of puree from Orange Fleshed Sweet
Potato affects the chemical and
sensory properties of the puree is the back
ground reason for this study being undertaken.
1.3 JUSTIFICATION
OF THE STUDY
In Nigeria two-thirds of the populations
of children are developing Xerophthalmia, as a result of lack of vitamin A, and
these children die in not more than a year of losing their sight. The approach
of increasing the consumption of orange fleshed sweet potato has aided alleviation
of deficiency of vitamin A in Nigeria in which about 30% of children under the
age of six are suffering from the deficiency of vitamin A (Anderson et al., 2007; Egbe, 2012). Production of
Ready – to – Eat products such as purees from Orange Fleshed Sweet Potato will
help to reduce the quantity of sweet potato wasted due to inadequate storage,
reduce bulk during fresh root transportation and lead to products that are
convenient to serve.
The results of the study will express
the effect of cooking methods on the proximate and Sensory
properties of purees made from Orange Fleshed Sweet Potato Variety (Var. Umuspo
1); thereby recommend the best method of cooking with the highest nutrient
retention and best texture. Thus, this will greatly
be of interest and benefit to the food industries involved in the production
and processing of Orange Fleshed Sweet Potato purees, and as well, be of
benefit to mothers who can utilize it as a recipe for vitamin A supplement in
baby feeding.
1.4 OBJECTIVES OF THIS STUDY
General Objective:
The broad objective of the study is
to evaluate the effect of different cooking methods on the chemical, and sensory properties of Orange Fleshed
Sweet Potato (Var. umuspo 1 (King J).
Specific Objectives:
The specific objectives are to:
i.
Produce purees from Orange Fleshed Sweet Potato using different modes of
preparation (peeled steamed), (peeled boiled), (unpeeled steamed) and (unpeeled
boiled).
ii.
Determine the proximate composition
of the purees.
iii.
Determine the total carotenoid content of the
purees.
iv.
Evaluate the sensory properties of the purees.
.
Login To Comment