ABSTRACT
Results of the proximate composition showed significant differences (p<0.05) with high values of moisture content in the fried samples ranging between (28.44-31.01)% than roasted samples with range values of between (24.02-29.03)%; crude protein and fat were also high and had values ranging between (23.01-25.11)% and (19.63-30.01)% respectively. The minerals, phosphorus (P), sodium (Na), calcium(Ca), magnesium (Mg), iron (Fe), zinc (Zn), manganese (Mn), Copper (Cu) and potassium (K) had values ranging between (391.62-442.53)mg/100g, (54.21-71.42)mg/100g, (33.06-49.82)mg/100g, (33.15-44.27)mg/100g, (18.32-19.96)mg/100g, (5.81-6.22)mg/100g, (0.78-1.27)mg/100g. (0.13-0.62)mg/100g, (0.823.33-913.59)mg/100g respectively. Microbiological assessment showed presence of bacteria (Lactobacillus spp. and Bacillus spp.) and three fungi (Saccharomyces species). The chemical properties of fried and roasted edible palm weevil larva that were determined were pH, free fatty acids and thiobarbituric acid and their ranges at ambient temperature in brown paper. Aluminium foil and polyethylene packages were 5.31-6.00, 5.5-6.00 and 5.3-6.00. Refrigeration temperature was seen to be the best storage temperature for the processed weevils compared to the samples stored at ambient temperature. Samples packaged with polyethylene bag showed the best results.
TABLE OF CONTENTS
Title page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
List of Tables xi
List of Figures
xiii
List of Plates
xiv
Abstract
xv
CHAPTER 1: INTRODUCTION
1.1
Statement of the Problem 3
1.2
Justification of the Study 4
1.3
Objectives of the Study 4
CHAPTER 2: LITERATURE REVIEW
2.1
Global Bias on Entomophagy 6
2.2
Life Cycle of Rhynchophorus phoenicis
7
2.3 Factors that Affect the Development of Rhynchophorus phoenicis 8
2.4 Factors Affecting Seasonal Availability of
Edible Insects 9
2.5 Impact of Edible Insect on the Environment 10
2.6
Harvesting, Processing and Preservation Methods 11
2.7 Nutritional Benefits of Consuming Edible Palm
Weevil
Larvae
(Rhynchophorus phoenicis). 12
2.8
Sensory Aspects 14
2.9
Insect Foods and its Acceptance 16
CHAPTER 3: MATERIALS AND METHODS
3.1
Sources of Raw Materials 17
3.2
Sample Preparation 17
3.2.1
Preparation of control sample (unprocessed) Rhynchophorus
phoenicis 17
3.2.2
Processing of roasted Rhynchophorus phoenicis 17
3.2.3
Processing of fried Rhynchophorus phoenicis larvae 18
3.3 Proximate Composition Analysis 21
3.3.1
Determination of moisture content 21
3.3.2
Determination of crude protein content 22
3.3.3
Determination of fat content 23
3.3.4
Determination of ash content 24
3.3.5
Determination of total carbohydrate content
25
3.4
Physical Analysis of Palm Weevil Larvae
25
3.5
Mineral Content Analysis 25
3.5.1
Determination of calcium and magnesium 26
3.5.2
Determination of potassium and sodium 27
3.5.3
Determination of phosphorus contents 28
3.5.4
Extraction of the heavy metals 29
3.6.0 Determination of Vitamin Content 30
3.6.1
Determination of vitamin A content 30
3.6.2
Determination of vitamin C content 31
3.6.3
Determination of vitamin E content 32
3.7 Fatty
Acid Composition Analysis 33
3.7.1
Extraction of lipids 33
3.7.2
Fatty acid profile 34
3.8 Determination
of Amino Acid Profile 34
3.8.1
Defatting of the sample 35
3.8.2
Determination of nitrogen 35
3.8.3
Hydrolysis of the sample 36
3.8.4
Loading of the hydrolysate into analyzer 36
3.8.5
Method of calculating amino acid values 37
3.9 Determination of Chemical Properties of
Edible Palm Weevil Larvae
(Rhynchophorus
phoenicis) 37
3.9.1 Determination of pH 37
3.9.2 Determination of free fatty acid 37
3.9.3 Determination of thiobarbituric acid value 38
3.10 Microbiological Analysis 38
3.11
Sensory Evaluation Test 40
CHAPTER 4: RESULTS AND DISCUSSION
4.1.
Proximate Composition of Fried and Roasted Edible Palm Weevil Larvae
(Rhynchophorus
phoenicis) 41
4.2 Physical Characteristics of Fresh, Roasted
and Fried Edible Palm Weevil Larvae
(Rhynchophorus
phoenicis) 49
4.3
Mineral Composition of Fried and Roasted Edible Palm Weevil
(Rhynchophorus
phoenicis) Larvae 54
4.4 Vitamin Composition of Fried and Roasted
Edible Palm Weevil Larvae
(Rhynchophorus
phoenicis) 66
4.5
Fatty Acid Composition of Fried and Roasted Edible Palm Weevil Larvae
(Rhynchophorus
phoenicis)
70
4.6
Amino Acid Profile of Rhynchophorus phoenicis
Larva 79
4.7
The Physico-Chemical Properties of Edible Palm Weevil Larvae
(Rhynchophorus
phoenicis) during Storage 84
4.7.1
Effects of packaging and storage on the pH of processed edible
palm weevil larvae 84
4.7.2 Effects of packaging and storage on the free
fatty acid (FFA) content
of processed edible palm weevil larvae 88
4.7.3 Effects of packaging and storage on the
thiobarbituric acid
analysis (TBA) values of processed
edible palm weevil larvae 91
4.8 Microbial Analysis of Processed Edible
Palm Weevil Larvae (Rhynchophorus phoenicis)
Stored at Ambient and Refrigeration
Temperatures and Packaged with Brown Paper,
Aluminium Foil and Polyethylene Bag
94
4.9 Sensory Evaluation of Fried and Roasted
Edible Palm Weevil Larvae
(Rhynchophorus
phoenicis)
108
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 111
5.2 Recommendations 111
References 112
Appendices 127
LIST OF TABLES
Page
2.1: Edible
Insects and Description of their Sensory Properties 15
4.1: Proximate
Composition of Roasted and Fried Palm Weevil Larvae
42
4.2: Physical Properties of Roasted and Fried Edible
Palm Weevil
(Rhynchophorus phoenicis) Larvae 50
4.3: Mineral
Composition of Fried and Roasted Edible Palm Weevil
(Rhynchophorus phoenicis) Larvae 55
4.4: Vitamin Composition of Fried and Roasted Edible
Palm Weevil
Larvae (Rhynchophorus phoenicis)
67
4.5
Showing Comparison of Amino Acid
Concentration of Processed Edible Palm
Weevil Larvae with other Sources of
Protein 80
4.6 pH of
Processed Edible Palm Weevil Larvae (Rhynchophorus
phoenicis) in
different Packaging Materials
during Storage
85
4.7 Free Fatty Acid Content of Processed Edible
Palm Weevil Larvae (Rhynchophorus
phoenicis) in
different Packaging Materials during
Storage 89
4.8 Thiobarbituric
Acid Content of Processed Edible Palm
Weevil Larvae
(Rhynchophorus
phoenicis) in different Packaging Materials during Storage 92
4.9 Cultural And Morphological Characteristics of
Microbial Isolates Identified in the
Processed and Stored Edible Palm Weevil Larvae (Rhynchophorus phoenicis) 95
4.10
Biochemical Characteristics of Microbial
Isolates Identified In The Processed And Stored
Edible Palm Weevil Larvae (Rhynchophorus phoenicis) Samples 97
4.11 Effects of
Processing Methods on Microbial Analysis of Edible Palm Weevil Larvae
Packaged with Brown Paper during Storage
100
4.12
Effects of Processing Methods on Microbial Analysis of
Edible Palm Weevil Larvae
Packaged
with Aluminium Foil during Storage
102
4.13 Effects of Processing Methods on Microbial Analysis of Edible Palm Weevil
Larvae
Packaged
with Polyetyhlene during Storage
104
4.14 Result of Sensory Evaluation of
Fried and Roasted Edible Palm Weevil Larva
(Rhynchophorus
phoenicis) 109
LIST OF PLATES
Page
1
Fresh Edible Palm Weevil Larva 43
2
Fried Edible Palm Weevil Larva
44
3
Roasted Edible Palm Weevil Larva 44
4
Edible Palm Weevil Larva Packaged before Storage
86
LIST OF FIGURES
Page
3.1 Flow chart for processed Edible Palm
Weevil larvae (Rhynchophorus
phoenicis) 20
4.1: Fatty Acid Profile of Edible Palm Weevil
Larva (Rhynchophorus phoenicis) 71
4.2:
Effect of Roasting Time on the Amino Acid Concentration of Edible Palm
Weevil Larva (Rhynchophorus phoenicis) 82
4.3:
Effect of Frying Time on the Amino Acid Concentration of Edible Palm
Weevil Larva (Rhynchophorus phoenicis) 83
CHAPTER 1
INTRODUCTION
Food
security and safety, coupled with malnutrition has been a challenging area and
cause of concern for economic growth and welfare of humans globally. A good
number of people in the continent find it difficult to access and utilize
effectively the required food for healthy living (Benson, 2004). The limited,
insufficient and expensive nature of protein diets in developing countries and
Africa, most especially, brought about the importance of consuming insects as a
food source (Allotey and Mpuchane, 2003). The consumption of insects has also
been reported in continents like Latin America, Asia and Australia directly as
food or as a source of food over the years (Allotey and Mpuchane, 2003).
Insect’s successful nature generally and high biodiversity, with special
reference to their richness specie-wise, critical ecological functions and
animal biomass especially the freshwater and terrestrial insects is
overwhelming (Samway, 2005). Most insects are of value commercially as they
provide products for both animal and human consumption (FAO, 2009). Pemberton
(1999) reported the folk medicinal effects and solution that the anthropods
play in Korea and China as they were referred to as sources for drug
development having analgesic, diuretic, immunological, antibacterial and also
anti-rheumatic properties (Yamakawa, 1998).
The Edible Palm Weevil, Rhynchophorus phoenicis is one of the most consumed species of
insects in Africa. Larvae, pupa and adult stages of the weevil constitute an
important source of protein to many communities (Meutchieye and Niassy, 2014).
This insect is one of the topmost consumed Coleopteran of Curculionidae family
in Africa (Van-Huis, 2003; Van-Huis, 2005). Rhynchophorus
phoenicis are eaten fried, roasted, grilled, dried, raw or incorporated into
diets or weaning foods (Allotey and Mpuchane, 2003; Gashe et al., 1997). Insects generally contain abundant and rich source
of nutrients like minerals, vitamins, proteins, fat and oil (Siame et al., 1996; Motshegwe et al., 1998; Oliviera et al., 1976; Braide et al., 2009; Braide et al., 2010). Edible Palm Weevil, Rhynchophorus phoenicis could be hunted
for and harvested during dry and rainy seasons and by day or night in fallen
palms (Ogbalu and Williams, 2015). Larvae of the weevil are usually able to thrive
under favourable conditions, provided by the palms whose trunks are rich in
vitamins and other nutrients (Ekrakene and Igeleke, 2007).
Foods
are not only of immense nutritional value to consumers, but could also be ideal
and reliable sources of culture media for microbial growth. They therefore
become and serve as means and vehicle for most disease transmission (Ekrakene
and Igeleke, 2007). The entire sequence of food handling, from the producer to
the final consumer should be of utmost importance as microorganisms are liable
to affecting the quality of food and human health generally, not leaving out
contamination by disease-causing microorganisms as they can occur at any point
in the food handling sequence (Ekrakene and Igeleke, 2007; Prescott et al., 1999).
Rhynchophorus phoenicis in
many parts of Nigeria are cherished highly to an extent of being described by
native names as: Akwa-Ibom State-Nten, Edo State (Bini)- Orhu, Edo State (Eshan)-Okhin,
Delta State (Itsekiri)-Ikolo, Delta State (Urhobo)-Edon, Delta (Isoko)-Odo, Oyo
State (Oyo)-Awon, Osun State (Ilesha)-Ekuku, Anambra State (most parts)-Akpa
ngwo, Anambra State (Ihiala)-Nza, Abia State-Eruru ngwo, Benue State (Idoma)-Eko-ali
(Ekpo and Onigbinde, 2005). Control over the occurrence of potential hazard in
the food supply chain is a sine qua non in increasing the consumer confidence
in the safety of food (Ebenebe and Okpoko, 2015). A food material adjudged to
be a delicacy can be a pot of poison if it contains disease-causing pathogens.
It becomes imperative to assess microbiological qualities of food relished by
humans to ensure that the nutritive value is not devalued by its microbial
content (Ebenebe et al., 2015). Estimation
of microbial numbers in food is commonly used in the assessment of
microbiological quality of food or to validate the presumptive “safety” of
foods (Ebenebe et al., 2015). Also,
various processing methods could have effect on sensory and physico-chemical
qualities of this insect during storage. To that effect, this study involves
the palm weevil being subjected to analysis and checking the effect which
roasting and frying (at varied timing) has on the microbiological quality,
physico-chemical characteristics and sensory quality of the fried and roasted
weevil larvae during storage.
1.1 STATEMENT OF THE
PROBLEM
In
westernized societies, the consumption of insect was and still a taboo to many.
Insects have also failed to feature on the agendas of agricultural research and
development agencies worldwide. Until recently, references to insects for food
and feed have been largely anecdotal; they are still lacking from the diets of
many rich nations and their sale for human consumption remains part of a niche
food sector of novelty snacks (Huis et
al., 2013).
Diets
prepared from insects are little in many rich nations and there are few
validated information on the potential of insects as food and feed sources
which could reliably help in promoting insects and placing them highly on
research agendas and political investments globally are yet to be realized
(Huis et al., 2013). Moisture and
protein contents being high in Rhynchophorus
phoenicis could encourage spoilage by bacteria and fungi species that are hydrophilic
and proteolytic in nature. Poor processing and storage, marketing conditions, poor
hygiene, lack of exposure to heat treatment may contribute to the weevil’s contamination
and re-contamination (Braide and Nwaoguikpe, 2011). Thus, portraying the weevil
larva as a breeding ground and host of pathogenic microorganisms which in turn,
predisposes consumers to diseases.
1.2 JUSTIFICATION OF THE
STUDY
Edible
Palm Weevil, being a rich source of nutrient could go a long way in curbing the
problem of food insecurity. It is therefore important to emphasize insect
consumption. The larva stage of Rhynchophorus
phoenicis when processed, could improve the microbiological,
physico-chemical and sensory qualities during storage. This study therefore
could project the best processing method that could extend the shelf-life of
this particular food source and expose the preferable best packaging materials
among the brown paper, aluminium foil and polyethylene.
1.3 OBJECTIVES OF THE
STUDY
The
main objective of the study is to determine the effect of processing methods on
the microbiological, physico-chemical and sensory qualities of edible palm weevil
(Rhynchophorus phoenicis) larvae
during storage.
The
specific objectives include:
I.
To fry and roast palm
weevil at different times and determine the proximate composition of the raw
and processed edible palm weevil larvae.
II.
To evaluate the mineral
contents and the physical characteristics of the raw and processed edible palm
weevil.
III.
To determine the amino acid profile and fatty
acid composition of the processed larvae of Rhynchophorus
phoenicis
IV.
To determine the physico-chemical
properties of the processed edible palm weevil larvae during storage.
V.
To determine the
microbiological quality of the processed edible palm weevil larvae during
storage.
VI.
To evaluate the sensory
quality of the processed edible palm weevil.
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