ABSTRACT
The effects of reuse of African breadfruit (Treculia africana) seed oil on the physico-chemical properties of the oil and quality of food product fried with it was studied. Oil was extracted from Treculia africana seeds by solvent extraction method. The same oil was repeatedly used in frying sweet potatoes three times. The physico-chemical properties of the oil in fresh and reused forms and sensory analysis of the fried potato chips were determined. The performance of African breadfruit (Treculia africana) seed oil and fried product (potato chips) were compared to those of selected vegetable oils (sunflower and groundnut oil). The results showed that the free fatty acid of breadfruit oil decreased from 0.33 ± 0.01 % - 1.60 ± 0.00 %, iodine value decreased from 135.13 ± 0.00 g/100g - 94.37 ± 0.00 g/100g, peroxide value increased from 3.18 ± 0.00 mEq/kg - 11.8 ± 0.09 mEq/kg, saponification value decreased from 209.3± 0.16 mgKOH/g-179.3± 0.00 mgKOH/g, moisture content decreased from 0.20 ±0.00 % - 0.01 ± 0.00 %, specific gravity 0.92± 0.00, smoke point from decreased 180.0 ± 0.00 oC - 130.0 ± 0.00 oC, fire point from decreased 337.0 ± 0.00 oC - 208.0 ± 0.00 oC, flash point decreased from 279.0 ± 0.00 oc - 172.0 ± 0.00 oc. The fatty acid profile compositions of African breadfruit (Treculia africana) seed oil before and after frying varied from 58.51 ± 0.00 - 43.37 ±0.00 (Oleic acid), 22.56 ± 0.00 - 17.48 ± 0.00 (Linoleic acid), 0.26 ± 0.00 - 0.18 ± 0.00 (Linolenic acid). The physico-chemical properties of African breadfruit seed oil used for frying were observed to depreciate with reuse. This depreciation in physico-chemical properties was also observed in reused groundnut oil and sunflower oil. Consumer preference test through sensory analysis showed that potato chips fried with fresh frying oils were significantly (p<0.05) different from those fried with reused oil with respect to attributes of appearance, taste, aroma, mouthfeel, crispiness and general acceptability.
TABLE
OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of Contents vi
List of Tables ix
List of Figures x
List of Plates xi
Abstract xii
CHAPTER 1:
INTRODUCTION
1.1
Background
of the Study 1
1.2 Statement of the
Problem 2
1.3 Objectives
of the Study 3
1.3.1 General
objectives of the study 3
1.3.2 Specific
objectives of the study 3
1.4 Justification
of the Study 3
CHAPTER 2:
LITERATURE REVIEW
2.1 African Breadfruit (Treculia africana) 4
2.1.1 Utilization of breadfruit 5
2.1.2 Nutritional value of African Breadfruit 6
2.2 African Breadfruit Seed Oil 7
2.3 Groundnut
Oil 9
2.3.1 Physicochemical
characteristics of groundnut oil 10
2.3.2 Fatty
acids composition 10
2.3.3 Triacylglycerol
composition 11
2.3.4 Phospholipids 12
2.3.5 Sterols
12
2.3.6 Tocopherols
13
2.3.7 Phenolic
compounds 14
2.4 Frying
Quality of Groundnut Oil 14
2.5 Nutritional
Properties and Health Benefits of Groundnut Oil 15
2.5.1 Anti-inflammatory
activity 16
2.5.2 Antitumor
activity and anticancerous activity 17
2.5.3 Groundnut
oil and cardiovascular diseases 18
2.5.4 Protection
against alzheimer’s disease 19
2.5.5 Anti-diabetic
activities 20
2.6 Sunflower
Oil 21
2.5.1 Physical
properties: 22
2.5.2 Chemical
composition of sunflower oil 22
2.5.3 Benefits
of sunflower oil 23
2.5.4 Health
benefits 23
2.5.4.1 Improves cardiovascular system 24
2.5.5 Sunflower oil as emollient: 24
2.5.6 Restaurant and food industry uses 24
2.6 Oil
Extraction Process 25
2.6.1 Mechanical
extraction 25
2.6.2 Solvent
extraction 25
2.6.3 Aqueous
oil extraction 26
2.6.4 Enzymatic
assisted aqueous oil extraction 27
2.7 Antioxidants 27
2.7.1 Antioxidant operation and mechanisms 28
2.7.2 Oxidative stability in oils 29
2.7.3 Auto-oxidation 31
2.7.4 Photo-oxidation 31
2.8 Physico-Chemical
Properties of Oil for Consumption 31
2.8.1 Free
fatty acid 31
2.8.2 Peroxide
value 32
2.8.3 Iodine value 33
2.8.4 Saponification value 34
2.8.5 Smoke,
flash and fire points 35
CHAPTER 3:
MATERIALS AND METHODS
3.1 Sample Collection and Preparation 36
3.1.1 African
Breadfruit (Treculia africana) seed oil 36
3.1.1.1 Extraction
of oil from African Breadfruit seed 36
3.1.2 Other frying oil sources 37
3.1.3 Preparation of sweet potato for frying 37
3.2 Frying Procedure 38
3.3 Determination
of Physico-chemical Properties of African Breadfruit
Seed
Oil, Groundnut Oil, and Sunflower Oil 38
3.3.1 Moisture determination 38
3.3.2 Specific gravity 39
3.3.3 Smoke, flash and fire points 39
3.3.4 Iodine value 40
3.3.5 Peroxide value 41
3.3.6 Free fatty acid 42
3.3.7 Saponification value 42
3.3.8 Fatty acids profile 43
3.4 Quality Determination of Fried Potato
Chips 43
3.4.1 Sensory evaluation 43
3.5 Statistical
Analysis 44
CHAPTER
4: RESULTS AND DISCUSSION
4.1 Physicochemical Properties of African Breadfruit Seed Oil Groundnut and
Sunflower Oil 45
4.1.1 Moisture 45
4.1.2 Specific gravity 47
4.1.3 Smoke point 49
4.1.4 Flashpoints 51
4.1.5 Fire
point 53
4.1.6 Iodine value 55
4.1.7 Peroxide value 57
4.1.8 Free fatty acid 59
4.1.9 Saponification
value 61
4.2
Sensory Evaluation of Potato Chips Fried with African
Breadfruit
Seed Oil, Groundnut, and Sunflower Oil 63
4.2.1 Appearance 63
4.2.2 Taste 64
4.2.3 Aroma 65
4.2.4 Mouthfeel 65
4.2.5 Crispiness 66
4.2.6 Acceptability
66
4.3 Fatty
Acid Profile of Fresh and Reused African Breadfruit Seed
Oil,
Groundnut Oil and Sunflower 68
4.3.1 Changes
in unsaturated fatty acid composition of African breadfruit
seed
oil, groundnut oil and sunflower oil 68
4.3.2 Changes
in saturated fatty acid composition of African breadfruit
seed
oil, Groundnut oil and sunflower oil 71
CHAPTER 5:
CONCLUSION AND RECOMMENDATION
5.1 Conclusion 80
5.2 Recommendation 81
References 82
Appendices 98
LIST OF TABLES
Table Title Page
No.
4.1: Changes
in the percentage (%) moisture content of frying oil 46
4.2: Changes
in the specific gravity of frying oil 48
4.3: Changes
in the smoke point of frying oil (OC) 50
4.4: Changes
in the flashpoint of frying oil (OC) 52
4.5: Changes
in the fire point of frying Oil (OC) 54
4.6: Changes
in the iodine value of frying oil (g/100g) 56
4.7: Changes
in the peroxide value of frying oil (mEq/kg) 58
4.8: Changes
in the free fatty acid of the frying oil (%) 60
4.9: Changes
in the saponification value of the frying oil (mgKOH/g) 62
4.10: Sensory evaluation of potato chips fried with African
breadfruit
seed oil, groundnut and
Sunflower oil 67
4.11: Fatty
acid composition of fresh and reused African breadfruit
seed
oil 74
4. 12: Fatty
acid composition of fresh and reused groundnut oil 75
4. 13: Fatty
acid composition of fresh and reused sunflower oil 76
LIST OF FIGURES
Figure Title Page
No.
3.1: Flowchart of breadfruit seed oil production 37
LIST
OF PLATES
Plate No. Title Page
No.
4.1: Potato chips produced with
fresh African
breadfruit seed oil,
groundnut oil and
sunflower oil 77
4.2: Potato chips produced with
African
breadfruit seed oil, groundnut
oil and sunflower oil
used once 77
4.3: Potato chips produced with
African
breadfruit seed oil, groundnut
oil and sunflower oil
used two times 78
4.4: Potato chips produced with
African
breadfruit seed oil, groundnut
oil and sunflower oil
used three times 78
4.5: Extracted African breadfruit (Treculia africana) seed oil 79
CHAPTER 1
INTRODUCTION
2.1
BACKGROUND
OF THE STUDY
African
breadfruit (Treculia africana) is
an important staple food of a high economic value (Soetjipto and Lubis, 1981).
The seeds from the fruit are edible and can be used in making various dishes;
it can be boiled, pounded, fried, or mashed to make porridge; it can also be
processed into flour and used in bread and biscuit making (Amusa et al., 2002). Treculia africana (breadfruit) seed is a good source of
edible oil. Its seed is said to contain oil of about 20.83% when fully
extracted (Ajiwe et al., 1995). The
seed oil contains components ranging from hydrocarbon (mainly monoterpenes,
terpenoids, etc.), alcohol and ketene which could be said to be responsible for
its unique flavor. The volatile fatty acid composition of African breadfruit (Treculia
africana) contains an appreciable
quantity of fatty acid that increases during processing. African breadfruit
seed oil when processed, is also comparable to that of some conventional oils.
Therefore, the oil can serve as raw material for food and other relevant
industries (Nwabueze and Emenonye,
2016).
Frying remains one of the
popular and tastier ways of preparing food. Consumption of ready-made food is
in much demand in developing countries. If it is deep fried then its demand becomes
even higher. Frying enhances the sensory quality of food by formation of compounds rich in aroma, crust,
texture, and attractive colour, all appreciated by the consumers (Goswami et al., 2015). During frying, the oil is
usually heated to about 170 
to 220 .
These temperatures subject the oil to physical and chemical reactions which
will affect the oxidative degradation in the presence of air and moisture
(Moreira et al., 1999). The chemical
reactions including oxidation, hydrolysis, and
polymerization of unsaturated fatty acid that change the composition of the
frying medium (Mariod et al., 2006). These
reactions lead to the production of
degraded products like free fatty acids, hydro-peroxides and polymerized
triglycerides (Choe and Min, 2007). The rate of frying oil degradation
increases with the duration of its reuse. Thus, the more the oil is heated
during reuse, the more degradation takes place and the more toxic compounds are
formed in the oil (Romero et al.,
2006). The rate of changes in the physical and chemical characteristics of the
oil dictates the quality of the oil for human consumption.
The
quality of frying oil is of great importance with regard to quality of the
fried food as it can contribute some unique organoleptic and sensory
characteristics including flavour, appearance
and texture (Kochhar, 2001; Aladedunye and Przybylski, 2009).
1.2 STATEMENT OF THE PROBLEM
The practice of repetitive use of frying oil
before discarding is a widespread practice. This is usually done to cut down on
cost. Studies have shown that the quality of repeatedly heated frying oil
deteriorates, leading to the formation of undesirable chemical compounds in the oil (Pokorny,
1989). There are potential health hazards
generated by the consumption of oxidized products resulting from oils used
repeatedly in frying processes (Gotoh et
al., 2007). These undesirable substances formed have been linked to health
hazards like atherosclerosis and cancer (Shastry et al., 2011). This
study, therefore, seeks to establish the effect of reuse of African breadfruit
fruit seed oil for frying on the physicochemical
properties of the oil and quality of food product fried in it.
1.3 OBJECTIVES OF THE STUDY
1.3.1 General objectives of the study
The
general objective of this work is to determine the effects of re-use of African
breadfruit (Treculia africana) seed
oil on the physciochemical properties of the oil and the quality of food
products fried with it.
1.3.2 Specific objectives of the study
- To produce
breadfruit oil from African breadfruit (Treculia africana)
seed.
- To fry sweet potato
into chips using African breadfruit (Treculia africana)
seed oil.
- To determine the
suitability of breadfruit oil (Treculia africana) in frying operations
and compare with groundnut oil and sunflower oil.
- To determine the
physical and chemical properties of these frying oils reused in frying
- To
determine the fatty acid profile of these oil samples before and after
being used in frying sweet potato.
- To determine
consumer acceptability of potato chips fried with these oil in its fresh
and reused forms through sensory evaluation.
1.4 JUSTIFICATION OF THE STUDY
Knowledge
from this study will help understand the levels of quality deterioration in
frying oils during reuse and its effect on the quality
and acceptability of products fried with them. It will further increase
awareness on the health risks associated with the re-use of frying oil.
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