EVALUATION OF INSECTICIDAL AND ANTIOXIDANT PROPERTIES OF SELECTED INDIGENOUS SPICES ON

Treculia africana SEED PRODUCTS

BY

UGWUONA, FABIAN UCHENNA PG/MSc/07/42602

DEPARTMENT OF FOOD SCIENCE & TECHNOLOGY FACULTY OF AGRICULTURE

UNIVERSITY OF NIGERIA, NSUKKA

JULY, 2010.

iEVALUATION OF INSECTICIDAL AND ANTIOXIDANT

PROPERTIES OF SELECTED INDIGENOUS SPICES ON Treculia africana SEED PRODUCTS

A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of Master of Science Degree in Food Science

and Technology, University of Nigeria, Nsukka

BY

Ugwuona, Fabian Uchenna PG/MSc/07/42602

Department of Food Science & Technology

University of Nigeria, Nsukka

JULY, 2010.

iiAPPROVAL PAGE

This thesis has been approved for the award Master of Science degree

in Food Science and Technology, University of Nigeria, Nsukka.

By

………………………. DR. (MRS) J. C. ANI

Project Supervisor External Examiner

……………………… DR. (MRS). J. C. ANI

Head of Department Dean of Faculty

iiiCERTIFICATION

Ugwuona, Fabian Uchenna, a postgraduate student in the

Department of Food Science and Technology, Faculty of Agriculture,

University of Nigeria, Nsukka, has satisfactorily completed the requirements

for the degree of Master of Science (M. Sc.) in Food Science and Technology.

The work embodied in this thesis is original and has not been submitted in

part or full for any other diploma or degree of this or any other university.

…………………………………

Dr. J. C. ANI

Supervisor

………….…………………………

DR. (MRS). J. C. ANI

Head of Department

ivDEDICATION

This work is dedicated to God Almighty for giving me the inspiration to

persevere.

vACKNOWLEDGEMENT

My greatest thanks go to my project Supervisor, Dr. (Mrs.) J. C Ani for

her constant advice, assistance and technical involvement throughout the

course of this work. I must appreciate her husband for his fatherly care and

concern. I am also indebted to the entire staff of the Department of Food

Science and Technology, University of Nigeria, Nsukka for their assistance to

me at the various stages of this research work.

Also to be heartily acknowledged are my numerous relations,

colleagues and friends, my beloved wife, Eucharia, my mother, Mrs Agness

Ugwuona and a host of others, who have helped me financially and

otherwise

viTABLE OF CONTENTS

Title page ....................................................................................... i

Approval page ............................................................................... ii

Certification .................................................................................. iii

Dedication .................................................................................... iv

Acknowledgement ......................................................................... v

Table of contents ........................................................................... vi

List of figures ................................................................................ x

List of tables ................................................................................. xii

Abstract ........................................................................................ xiii

CHAPTER ONE: 1.1. Introduction ......................................................................... 1

1.2. Statement of the Problem ...................................................... 3

1.3. Justification for the Study .................................................... .3

1.4. Significance of the Study……………………………………. .......... .3

1.5. Aims and Objectives of the Study .......................................... 4

CHAPTER TWO: 2.0 Literature Review ..................................................................... 5

2.1. Structure and Chemical Composition of Grains ...................... 5

2.2. Important Points for Safe Storage of Grains ........................... 5

2.3. Damages Caused by Food Grain Storage Pests ........................ 6

2.4. Sources of insects that infest Stored Grains ............................ 7

2.5. Detection of Insect Infestation ................................................. 8

2.6. Major Storage insect Pests of Food Grains ............................... 8

2.7. Effect of Thermodynamic Properties of the Environment on Pest

Infestation of stored Grains ............................................................ 11

2.8. An Overview of Pest Problems and management in the

Tropics .......................................................................................... 13

2.9. Control and Management of Storage insect Pests of

grains and flours ............................................................................ 14

2.10. Use of Plant Materials and Powder for insect Control in stored grains

...................................................................................................... 16

vii2.11. Use of Plant extracts and Oils for Control of Insect Pests of stored

grains ............................................................................................ 17

2.12. Lipid oxidation…………………………………………………...........18

2.13. Functions of antioxidants in foods…………………………… ..... 20

2.14.Natural antioxidants ............................................................. 21

2.15. Assessment of antioxidants activity in food system ................ 21

2.16. Botany, ecology and distribution of Tamarindus indica Linn

.....................................................................................................22

2.17. Chemical composition and uses of fruits and seeds of Tamarindus

Indica Linn ...........................................................................................23

2.18. Ecology, botany and distribution of African nutmeg (Monodora

myristica [Gaertn]) ................................................................................24

2.19. Chemical composition and uses of African nutmeg ............... 25

2.20. Botany ecology, and distribution of Xylopia aethiopica Dunal A.Rich

(Ethiopian Pepper) ......................................................................... 25

2.21. Chemical composition and use of Xylopia aethiopica (Dunal) A.Rich 25

2.22. Ecology, botany and distribution of Piper guineense (Schum &

Thonn)(African black pepper) ...............................................................26

2.23. Uses of Piper guineense (Schum & Thonn)................................26

2.24 Ecology, Botany and distribution of African breadfruits (Treculia

africana Decne) ............................................................................. 26

2.25 Chemical composition and uses of Treculia africana Decne seeds 27

CHAPTER THREE: 3.0 Materials and Methods ......................................................... 29

3.1. Materials ................................................................................. 29

3.2. Experimental design ................................................................ 29

3.3. Extraction of the spice pulp or oils for storage study ............... 29

3.3.1 Extraction of Tamarindus fruit pulp………………… ................. 29

3.3.2 Extraction of African nutmeg for oil .........................................29

3.3.3 Extraction of spice oils from Ethiopian pepper (Xylopia aethiopica)

(Dunal) A.Rich and African black pepper [piper guineense (Schum & Thonn)].

...................................................................................................... 30

3.4. Cleaning and processing of Africana breadfruit ....................... 30

viii3.5. Rearing of the insect pests ...................................................... 30

3.5.1 Post-exposure toxicity ........................................................... 31

3.5.2 Fumigant toxicity .................................................................. 31

3.5.3 Contact toxicity .................................................................... 31

3.6. Storage stability of Treculia africana Decne seed dhals and flour treated

with spice extracts ......................................................................... 32

3.7. Antioxidant activity in stored Treculia africana Decne seed dhals and

flour .......................................................................................... 32

3.8. Preparation of aqueous and ethanolic extracts of spices for antioxidant

study ............................................................................................ 33

3.9. Assessment of the reducing power of the spices

materials…………………………………………… .................................. 33

3.10 Total phenol content determination ....................................... 34

3.11 Determination of radical scavenging activity .......................... 34

3.12 Proximate analysis of samples ............................................... 34

3.13 Digestion and analysis of minerals ........................................ 35

3.14 Data analysis ........................................................................ 35

CHAPTER FOUR 4.0 Results and Discussion ....................................................... 36

4.1 Nutrient composition of Treculia africana seed ..................... 36

4.2 Proximate composition of four spice samples used in the study 38

4.3 Mineral contents of the test spices ....................................... 39

4.4 Yield of oils from the spices .................................................. 40

4.5 Insecticidal activities of the spice materials .......................... 41

4.6 Effect of Monodora myristica Gaertn (African nutmeg) oil

against adult T.castaneum Herbst ............................................41 4.7 Effect of Monodora myristica (Gaertn) oil on S. zeamais (Motsch) 44

4.8 Effect of essential oil from Xylopia aethiopica Dunal A.Rich on survival of adult T. castaneum Herbst ....................................................47

4.9 Effect of Xylopia aethiopica Dunal A.Rich on survival of adult S. zeamais Motsch .........................................................................51

4.10 Effect of Piper guineense Schum & Thonn oil on T. castaneum Herbst ...................................................................................................55

ix4.11 Effect of Piper guineense Schum & Thonn oil on S. zeamais Motsch

...................................................................................................57

4.12 Antioxidant Activity of the spices .......................................... 60

4.13 Comparison of TBA value of Treculia africana Decne seed treated with Monodora myristica Gaertn spice oil. ........................................60

4.14 Comparison of TBA values of Treculia africana Decne seed treated with Xylopia aethiopica spice oil .................................................. 66

4.15 Effect of Piper guineense Schum & Thonn oil on TBA values of Treculia Africana Decne seed dhals and flour ................................... 71

4.16 Comparison of TBA values of Treculia africana Decne seed treated with aqueous extracts from Tamarind fruit pulp ................... 76

4.17 Comparison of mean TBA values of Treculia africana Decne seed dhals treated with aqueous extracts of Monodora myristica Gaertn, Xylopia aethiopica Dunal A.Rich, Piper guineense Schum & Thonn and Tamarind indica Linn ................................................................82

4.18 Antioxidant activities of the test spice water-extracts from the test spices as

Measured by the reducing power capacity . .......................... 84

4.19 Total phenol content............................................................. 87

4.20 Free radical scavenging ability of the spice extracts against

1, 1 Diphenyl – 2 – picryl hydrazyl (DPPH). ........................... 89 4.21 Comparison of the radical scavenging activities of the tested spice

material against 1,1 – Diphenyl - 2 – picryl hydrazyl (DPPH) . 101

CHAPTER FIVE Conclusion and Recommendation ................................................. 104 References ............................................................................... 106 Appendices ............................................................................. 121

xLIST OF FIGURES

1. Effect of Monodora myristica Gaetn oil concentration on TBA value of

Treculia africana Decne seed dhal during storage at 26±20c. ..... 63

2. Effect of Monodora myristica oil concentration on TBA value of

Treculia africana seed flour during storage at 26±20c. .............. 64

3. Effect of Xylopia aethiopica oil concentration on TBA value of

Treculia africana seed dhal during storage at 26±20c. .............. 68

4. Effect of Xylopia aethiopica Dunal. A. Rich oil concentration on TBA value

of

Treculia Africana seed flour during storage at 26±20c. .............. 69

5. Effect of Piper guineense oil concentration on TBA valve of

Treculia africana seed dhal during storage at 26±20c ................ 73

6. Effect of piper guineense Schum & Thonn oil concentration on TBA value

of

Treculia africana seed flour during storage at 26±20c. ................ 74

7. Effect of Tamarindus indica fruit pulp concentration on TBA value of

Treculia africana Decne seed dhal during storage at 26±20c. ...... 78

8. Effect of Tamarindus inidca fruit pulp concentration on TBA value of

Treculia africana seed flour during storage at 26±20c ...................79

9. 8. Effect of aqueous extracts of Monodora myristica Gaertn, Xylopia

aethiopica Dunal A.Rich Tamarindus indica Linn and piper guineese

Schum & Thonn spices on TBA values of Treculia Africana Decne seed

dhal during storage at 26±20c………………………………………….. 83

10 Antioxidant activities of water extracts of spices at different

concentrations as measured by reducing power. ……………………86

11. Total phenolic (tanic acid equivalent) content of aqueous and ethanolic

extracts of the spices …………………………………….88

12.DPPH radical scavenging activity of water extracts from Xylopia

aethiopica whole fruit residue. ………………………………………………91

13.PPH radical scavenging activity of water and ethanol extracts from

Xylopia aethiopia seed. ............................................................ 92

xi14.DPPH radical scavenging activity of water and ethanol extracts from

Xylopia aethiopica fruit pod. ...................................................... 93

15. DPPH radical scavenging activity of water and ethanol extracts from

piper guineense whole fruit . .................................................... 94

16.PPH radical scavenging activity of water extracts from piper guineense

fruit residue. ............................................................................. 95

17.DPPH radical scavenging activity of water and ethanol extracts from

Monodora myristica fruits. ........................................................ 97

18. DPPH radical scavenging activity of water extract from Monodora

myristica fruit residue ........................................................... 98

19.PPH radical scavenging activity of water and ethanol extracts from

Tamarindus Indica fruit (pod). ................................................... 100

xiiLIST OF TABLES

1. Parameters for assessing the types of pests causing damage to food

grains. ………………………………………………………………….7

2. Nutrient composition of underhulled and dehulled Treculia africana

Decne seeds before and after six (6) months of storage.

………………………………………………………………………………..37

3. Proximate composition (%) of the fruits of Xylopia aetheopica Dunal

A.Rich, Piper guineense Schum & Thonn, Tamarindus indica (Linn)

and Monodora myristica Gaertn ……………………..39

4. Mineral content (%) of Xylopia aethiopia Dunal A.Rich, piper

guineense Schum & Thonn, Tamarindus Indica Linn and Monodora

myristica Gaertn fruits ………………………………….40

5. Yield of oil (extracted with n-hexane) from Xylopia aethipiopia Dunal

A.Rich, piper guineense Schum & Thonn and Monodora myristica

Gaertn ……………………………………………………..40

6. Mortality (%)of T castaneum Herbst in broken Treculia seeds (15g)

protected with Monodora myristica Gaertn oil in 70% filled glass via.

…………………………………………………………………………42

7. Fumigant toxicity (%) of Monodora myristica Gaertn oil against T.

castaneum Herbst on broken Treuclia africana Decne seed at 10%

filling in 1500-ml fumigation chamber cumulative mean

S.D…………………………………………………………………………44

8. Mortality (%) of adult S. zeamais Motsch in whole Treculia africana

seeds (20g) treated with Monodora myristica Gaertn oil in 70% filled

glass vial. ……………………………………………………….. 45

9. Fumigant toxicity (%) effect of Monodora myristica Gaertn oil against

Sitophilus zeamais Motsch in whole Treculia seeds at 10% filling in

1500-ml fumigation chamber……………………………46

10. Effect of Monodora myristica Gaertn oil on survival of Tribolium

castaneum Herbst and Sitophilus zeamais Motsch after 24 hours of

post-exposure……………………………………………………………46

xiii11. Mortality (%) of adult T. castaneum Herbst in broken Treculia

Africana Decne seeds (15g) protectes with Xylopia aethiopica Dunal

A.Rich oil in 70% filled 50ml glass vial.…………………….48

12. Toxicity of Xylopia aethiopica Dunal A.Rich oil against T. castaneum

Herbst on broken Treculia africana Decne seeds at 10% filling in

1500-ml fumigation chamber

%………………………………………………………………………………50

13. Mortality (%) of adult S. zeamais Motsch in broken Treculia africana

Decne seeds (15g) treated with Xylopia aethiopica Dunal A.Rich oil in

70% filled glass vial. …………………………………….52

14. Fumigant toxicity (%) of Xylopia aethiopica Dunal A.Rich oil against

Sitophilus zeamais Motsch on whole Treculia africana seeds at 10%

filling in 1500-ml fumigation

chamber……………………………………………………………………54

15. Effect of Xylopia aethiopica Dunal A.Rich oil on survival of Tribolium

castaneum Herbst and Sitophilus zeamais Motsch after 24

hours…………………...............................................................55

16. Mortality (%) of adult T. castaneum Herbst in broken Treculia africana

Decne seeds (15g) protected with piper guineense oil in 70% filled

glass vial. …………………………………………………….56

17. Fumigant toxicity of piper guineense Schum & Thonn oil against T.

castaneum Herbst on broken Treculia africana Decne seed at 10%

filling in 1500-ml fumigation chamber………………………57

18. Mortality (%) of adult S. zeamais Motsch in whole Treculia seed

protected with Piper guineense Schum & Thonn oil in 70% filled glass

vial. ………………………………………………………………..58

19. Fumigant toxicity (%) of Piper guineense Schum & Thonn oil against

adult Sitophilus zeamais Motsch on Treculia africana Decne seeds at

10% filling in 1500ml fumigation

chamber……………………………………………………………………59

xiv20. Effect of Piper guineense Schum & Thonn oil on survival of

Tribulium castaneum Herbst and Sitophilus zeamais Motsch after 24

hours of exposure. ………………………………………………..60

21. Summary of significance (P

xvMonodora myristica, Piper guineense, Xylopia aethiopica and

Tamarindus Indica fruit pulps.

……………………………………………………………………………..84

31. Free radical 1,1 diphenyl – 2- picrylhydragyl (DPPH) scavenging

activity of the spice extracts. …………………………………………102

xviAbstract

Treculia africana seeds, Tribolium castaneum and Sitophilus zeamais insect pests, and Tamarindus indica, Xylopia aethipica, Piper guineense and Monodora myristica spices were procured for the study. Two kilogrammes of Treculia africana seeds and 400g of each of the spices were dried at 50oC in hot-air oven to about 12.8% moisture content. Dried Treculia africana seeds (2kg) were used for insecticidal properties. Another 5kg of Treculia africana seeds were parboiled in excess boiling (1000C) water for 15 minutes, drained out of water and dehulled to produce seed dhals. The seed dhals (4kg) were oven-dried at 50oC to about 12.8% moisture content, and 1.5kg weight of the seed dhal milled into flour. The seed dhals and flour were used for antioxidant study. Oil was extracted from 200g of each of Piper guineense, Xylopia aethiopica and Monodora myristica fruits with 500ml n-hexane, using maceration techniques. Fruit pulp was extracted from 200g of Tamarindus indica fruits, using 50ml of distilled water. Ethanolic and water extracts of spices were prepared using 1g of each spice to 20ml of ethanol or distilled water. Undehulled T. africana seeds (20g each) were treated with different concentrations of each spice oil (0, 0.25, 0.5. 0.75 1.0 ml) or fruit pulp (0, 1, 2, 3, 5g), and each treatment was infested with ten adults of T. castaneum or S. zeamais and stored for contact (10 days), fumigant (74 hours) and post-exposure (48 hours) toxicity tests Samples (100g) of Treculia africana seed dhals and flour were treated with different concentrations of spice oils (0, 0.5, 1.0, 1.5, 2.0 ml) or fruit pulp (0, 1, 2, 3, 5g) and stored at 26 + 2oC for 4 months for oxidation study. Ethanolic and water extracts of the spices were screened for total phenolic content, reducing capacity with FeCl3, and scavenging activity against 1, 1 diphenyl-2- picryl hydrazyl (DPPH). Tamarindus indica fruit pulp did not exhibit insecticidal effect on both Tribolium castaneum and Sitophilus zeamais. Monodora, Xylopia and Piper guineense oils showed dose-dependent insecticidal effects on T. castaneum and S. zeamais. Toxicity tests showed that insect mortality increased with storage time and was higher for S. zemais than for T. castaneum at all spice oil concentrations. Piper guineense oil had the highest mean mortality (%) for both insects, followed by Xylopia oil and then Monodora oil. The spice oils exhibited dose-dependent antioxidant property on Treculia seed dhals and flour as evident from the mean thiobarbituric acid values which decreased with increasing oil concentrations. Mean thiobarbituric acid (TBA) values for treated seed dhals and flour after 4 months of storage ranged from 2.5 to 3.1 ppm Malonaldehyde while the untreated samples had 4.6 ppm malonaldehyde. Ethanolic and water extracts of the spices exhibited antioxidant capacity in total phenolics, in reducing power with FeCl3, and in scavenging 1, 1-diplhenyl-2-picryl hydrazyl (DPPH) radical. Tamarindus indica fruit pulp had the highest phenolic content, followed by Monodora myristica, Piper guineense, and Xylopia aethiopica. Antioxidant capacity of the spices was in the order: Piper guineense > Xylopia aethiopica > Tamarindus indica > Monodora myristica. The IC50, final concentrations (mg/ml) of dry spice extracts required to decrease the initial concentration of DPPH to 50% in the corvettes, compared scavenging potency of the extracts with DPPH. Ethanolic extract of Monodora myristica had the least IC50 value of 2.5 while water extract of Xylopia fruit had the highest IC50 value of 154 in scavenging DPPH.

1CHAPTER ONE

1.1 INTRODUCTION

Evidence of malnutrition is increasing in many parts of the world, particularly in

developing countries, and unsatisfactory feeding has been shown to be common in such

countries (UNICEF, 1989; WHO, 2000). Millions of people, particularly children are affected

by inadequate food intake (UNICEF, 1989). Protein- energy malnutrition constitutes the

major nutritional problem of these children and this impairs their growth, health, mental

capability and productivity (Spur et al., 1979; Martonel, 1992; Bertman and Kawachi, 2000;

Ivanovic et al., 2002; Ischara, 2005).

Differences in adaptation of food crops and animals to various agro-ecological

regions across the globe and the incessant natural disasters including fire outbreak, flood,

draught and pest infestation pose problems of food insecurity worldwide. The world

population put at 8.3 billion is increasing at a geometrical progression at the expense of fall in

food supply (WHO, 2000). There is therefore the need for adequate storage of food produced

at the season of plenty against the period of scarcity; and adequate and regular distribution of

food produced from regions of harvest to regions where they are not available. Regions

would be at economic advantage in producing what they have the most favourable conditions

for. There would be more food security among nations.

Worldwide, effort is currently geared towards massive production, storage and

distribution of grains as economically cheap source of proteins (Peace et al., 1988; Nkama

and Gbenyi, 2001). Actually grains are wide and are nutritiously rich (Pascual, 1978) but are

adversely affected by pest infestation both in the fields and in stores after harvest. Also most

legumes and oilseeds, because of their high oil contents, when processed become rancid on

storage due to autoxidation (Attman et al., 1986). Common pests of grains in store include

microorganisms, rodents, mites and insects. Insect damage in stored cereals and pulses may

account for up to 10 to 40% in countries where modern storage technologies have not been

introduced (Shaaya et al., 1997) Currently, the measures to control autoxidation and pest

infestation in grain and dry food products rely heavily on the use of gaseous and liquid

synthetic Pesticides, which pose health hazards (to warm blooded animals) and a risk of

environmental contamination (Snelson, 1984).

Recently, chemicals in use for insect control have decreased drastically as problems

of insect resistance have intensified and mounting social pressures against the use of toxic

chemicals have limited the introduction of new compounds (Nakakita and Winks, 1981; Lale,

21995; Shaaya, 1997). At present methyl bromide and phosphine are still in use but methyl

bromide has been identified as a major contributor to ozone depletion which cast doubt on its

future use for insect control (WHO, 1995). Also there has been a repeated indication that

certain insects have developed resistance to phosphine, which is widely used today (Nakakita

and Winks, 1981; Mills, 1983; Tyler et al., 1983).

Application of antioxidants is one of the technically simplest ways of reducing

autoxidation of lipids (Karpinska et al., 2001). The antioxidants can be of synthetic and

natural origin. Some synthetic antioxidants including BHA and BHT might be dangerous for

living organisms (Attmann et al., 1986). Naturally derived antioxidants are considered better

and safer than synthetics (Dorko, 1994). There is the need to develop ecologically friendly

methods, which will use natural compounds, and yet be simple and convenient to use. A wide

variety of higher plants may provide new sources of natural antioxidants (Dorko, 1994;

Madsen and Bertelson, 1995), pesticides and antifeedants (Grainge and Ahmed, 1988;

Arnason et al., 1989; Ananthakrishnan, 1992). Among the many plant derived substances

studied are spices and extracts of spices which have various effects on insect pests, including

stored-product insects (Grainage and Ahmed, 1988; Jacobson, 1989; Shaaya et al., 1991).

Insect control agents of plants origin are broad spectrum in action, safe to apply, non-

persistent and easily processed (Talukder and Howse, 1995). The same is true of antioxidants

of plant origin. Several studies have shown that they offer good prospects for protection of

stored products against rancidity development and damage by pests (Nawrot et al., 1986,

Sharaby, 1988; Khanam et al., 1990, Serit et al., 1992; Telukder and Howse, 1994).

In view of the various activities of powders, extracts and oils of spices against

rancidity development and some insect pests of stored grains, pulp powder and oil extracts

from the fruits of tamarind, Ethiopian pepper, African black pepper and African nutmeg were

screened for antioxidant and insecticidal properties on the seeds of African breadfruit

(Treculia africana). These four spices are indigenous spices in Nigeria. Tamarind is popular

in the North while the other three are more popularly used in the Eastern and Western parts of

the country. These spices have been reported (Iwu, 1993) to have many medicinal values

apart from their flavouring effects. The pulp of the fruits of tamarind is used in traditional

flavouring while the entire fruit of African nutmeg is also used for food flavouring.

African breadfruit (Treculia africana) is native to tropical region and produces

abundant quantity of fruits. The seeds are of high nutritional value and are currently a

potential source of nutrient in the diet of many Nigerians (Iwe and Ngoddy, 2001). The flour

3is also a good complement to wheat flour in bakery products (Giami et al., 2004).

Unfortunately the seeds (dehulled and undehulled) and flour deteriorate easily on storage, due

partly to oxidation of lipids, lipolytic moulds and insect pests, namely Tribolium casteneum

and Sitaphilus orizae (Adindu and Williams, 2003). A preliminary study here in the tropics,

in the laboratory, revealed that Sitophilus zeamais ferociously attacked the seeds instead of

sitophilus orizae, a temperate pest.

This causes a lot of losses of the product and reduces its supply. Attempts were made

in this work to evaluate the insecticidal and antioxidant properties of pulp powder and oil

extracts of tamarind, Ethiopian pepper, African black pepper and African nutmeg fruits on

African breadfruit. Two primary insect pests, Tribolium castanuem and Sitophilus zeamais, of

stored Treculia African Decne were used for the insecticidal study.

1.2 Statement of the problem

Common grains in use for food are becoming too expensive and scarce. Alternative

food sources from some, unconventional grains which are lost periodically to insect

infestation need to be protected on prolonged storage for more exploitation for food use. This

would also increase the use of such grains globally. Treculia Africana Decne (African

breadfruit) seed is one of such less common oilseeds that are periodically being lost to insect

pest infestation and also become rancid on storage. It is, therefore, necessary to exploit some

spice materials to protect this grain legume from insect infestation and autoxidation.

1.3 Justification for the Study

There is the need to increase food supply from under-utilized food crops such as

Treculia africana Decne seeds in the tropics. Treculia africana is a good source of protein,

readily available, though not cheap but easily becomes rancid, and gets damaged by insect

pests on storage. The seeds are seasonal in supply. The undehulled and dehulled seeds need

to be protected against storage insect pests while the dehulled seeds and seed flour need to be

protected from rancidity development to extend its shelf life for more food application across

the globe.

1.4 Significance of the study

This work will improve storage and utilization of whole, dhal and flour of Treculia

africana seeds in homes and industries. It will facilitate exportation and industrial uses of the

food crop within and outside the tropics. It will create employment opportunities for many

people; and will lead to the development of new products based on Treculia africana seed.

41.5 Aims and Objectives

Based on the aforementioned problems, the objectives of this study are to:

i. Extract fruit pulp and oils from the spices namely Tamarind, African nutmeg,

Ethiopian pepper and African black pepper;

ii. Evaluate insecticidal properties of the spice pulp and oils against two prominent

(primary) insect pests (Tribolium castaneum Herbst and Sitophilus zeamais Motsch)

of African breadfruit, using three different approaches;

iii. Evaluate the antioxidant properties of the spices and their extracts (pulp and oils) on

stored dhals of African breadfruits;

iv. Assess the effects of such treatments on the composition and selected properties of African breadfruit

5CHAPTER TWO

2.0 LITERATURE REVIEW

2.1 Structure and Chemical Composition of Grains

A grain is a living biological cereal material that respires and can germinate. Grains

metabolize through respiration and this results in decrease in dry weight, oxygen

consumption, evolution of carbon dioxide and heat. The rate of metabolic activity of grain

depends on its moisture content and temperature; and will increase with increase in

temperature range of 40oC to 50oC. At this temperature range, the viability as well as the rate

of respiration decreases significantly (Chakruverty, 2004). Structurally a grain consists of an

outer husk which covers the seeds components: pericarp, seed coat, aleurone layer; germ and

endosperm. The husk is composed of strongly lignified floral integument which reduces the

rate of drying up of the seed. The embryo (germ) tissues consist of living cells which are very

sensitive to heat. The endosperm fills most inner part of the seed and consists of thin-walled

cells filled with protoplasm and starch granules. The endosperm is a food reserve for the seed

and is used up during development of the seedling.

Chemically the grain is composed of both organic and inorganic compounds, which

include carbohydrates, proteins, vitamins, fats, water, mineral salts and enzymes. Grains are

rich in protein, with few oilseeds and legumes rich in fats and oil. The pericarp contains

cellulose and pentosan; the aleurone layer is composed of mainly albumen and fat. The

endosperm has the highest content of carbohydrate in the form of starch but very low in

protein and cellulose. The germ has the highest amount of fat and protein but a small content

of carbohydrate in the form of sugar. However this is embedded with the seed enzymes.

2.2 Important points for safe storage of grains

The thermodynamic properties of the environment affect the storage life of grains. The

principles of grain storage are based on these properties. Therefore, these properties as they

relate to grain behaviour must be understood to be manipulated for safe storage of grain.

(Food Industry, 1979). Salient points to use and be worked on for safe storage of grain

include:

i. Moisture content of grain below 13% arrest the growth of most microorganism

and mites.

6ii. Moisture content below 10% limit development of most of the stored grain insect

pests.

iii. Moisture content within a grain bulk is hardly uniformly distributed and is

changeable.

iv. Mites do not develop below 50C.

v. Most of the storage fungi do not develop below 00C.

vi. The effect of temperature on an organism can be correlated with the amount of

grain moisture. The rate of respiration of grain, the growth of microorganisms,

and biochemical reaction during storage also increase, to some extent, with

temperature (Sinha, 1973)

2.3 Damages Caused by Food Grain Storage Pests

The major pests in stored grains and flour are insects, microorganisms and rodents

and their damage to grains/four is in sequence viz:

- Insects and rodents eat and contaminate the stored commodity(s); - Insects and rodents produce uric acid, faecal matter, cast skin and fowl odour,

and introduce fungi, bacteria and larvae on the food material. (s);

- Microorganisms including fungi and bacteria deteriorate and alter the chemical constituents of the food grain and flour;

- Microorganism, insects and rodents produce other harmful substances into the product. Some fungi produce mycotoxins;

- Clumping and clogging together of the product with change in colour and presence of stinking putrid odour;

- Reduction in seed viability especially if the germ is affected; - Contamination of the product with poisoning excreta, uric acid, mycotoxins

and other toxins, mould, bacteria and even viral cells.

Qualitative damage of food grains resulting from storage pest infestation are assessed

(Food Industry, 1979) by some parameters which are listed in Table 2.1.

7Table1: Parameters for assessing the types of pests causing damages in food grains.

S/N Evidence of insect damage Evidence of mould

damage

Evidence of mite

damage

1 Moisture Moisture Foul odour

2 Uric acid Apparent uric acid Guamine

3 Exuvae Discoloration Allergens

4 Chitins Mycotoxins ND

5 Dead insects Thermogenesis Pathogen vectors

6 Infested odour Musty odour Debries

7 Frass Loss of Viability ND

8 Killed germ ND ND

9 Microflora ND ND

Source: Food Industroy, 1979. ND = not determined

2.4 Sources of insects that infest stored grains

There are mainly five sources of insect infestation of food grains in the store. These

include the field, already infested grains, infested transport vehicles, stocks, and granaries

(Howe, 1965).

1. The field: Insects may attack the crops in the field, and grains from such crops may

continue being infested and attacked by such insect pests when harvested. Bruchid

beetle known to attack stored pulses also infest the crop in the field prior to harvest

(Booker, 1967; Taylor and Aludo 1974; Hagstrum, 1985; Patraik et al., 1986). Grains

affected by insects in the field when brought to store and silos continue being attacked

by the same set of insects probably because the insect eggs or and larvae have been

harvested along with the grain. With the eggs and larvae only, the infestation may be

hardly noticeable but once the larvae continue feeding to pupate, grain damage

become very prominent in the lot.

2. Infested Gunnies (Gunny-Sacks): Once the gunny or container is infested, there is

no need bringing wholesome grains into it. Even if sound and new granary is used to

store the freshly harvested grain, the insects hiding in the seam of the old containers

and in the sacks will attack the grains and continue infestation. Insect population is

known to breed in commodity residues in storage silos ( Mouro, 1969).

83. Infested Transport: The infestation condition of the transport system and

containers are of paramount importance in checking insect infestation of grains in

stores. The transport used to carry harvested grains when infested with insects from

old stocks can transfer the pests to wholesome ones if not fumigated after each use.

Evidence has shown that insect populations grow in commodity residues in farm

equipment and vehicles.

4. Infested granaries and Stores: The insects present in the cracks and crevices of the

wall or that hibernate in the structures may emerge out and attack the grains. The

cracks and crevices therefore should be plugged and empty granaries and stores

should be thoroughly cleaned and fumigated before use.

5. Infested Stocks: Cases abound where infested stocks are brought in contact with

wholesome ones in stores where the insects quickly attack the wholesome ones

(Boumans, 1985).

2.5 Detection of insect infestation

In stores and granary insect infestation on stored grain legumes can be detected by the

following methods (Chakraverty, 2004):

1. Visual examination of surface holes on the grain;

2. Floatation method, where the grains are soaked in water; and damaged grains and egg

float. This can be seen with naked eye;

3. Staining with appropriate dyes for detecting egg plugs;

4. Uric acid method;

5. Gelatinization methods;

6. Phenol method;

7. Ninhydrin method;

8. Aural method;

9. Carbondioxide (C02) as an index of infestation;

10. X-ray method to detect cells;

11. Cracking floating seeds to ensure pest types and stage of infestation.

2.6 Major storage insect pests of food grains

The major insect pests of food grains in storage in the tropics are beetles (Order

Colleoptera) belonging to a diversity of insect families and a few moths (Order Lepidoptera)

9belonging to the family Pyralidae (Appert, 1987; De Lima, 1987; Hill and Waller 1990). A

few mites (Subclass Acari) also damage stored grains. These storage insect pests, regardless

of families and order, can be grouped according to their mode of action, feeding habits and

activities into the following categories.

1. Major Insect Pests: These are those that attack the grain directly and destroy them

completely. Common examples are Khapra larvae, Rhizoperdhasp and Siltohollus

Spp.

2. Minor Insect Pests: These are those that follow and continue the destructions

already started by the major insect pests, but they cannot directly start attacks and

destroy the grains on their own. Common examples include Leophileous minutes and

oryzaphillus surinanmensis (Hill and Waller, 1990).

3. Incidental Insect Pests: These are those that may or may not harm the stored food

grain. In most cases they contaminate the grains only by their presence.

4. Parasites and predators: These are group of insects that feed on other insects or

organisms in the store. They are parasites when they solely depend on their hosts,

second animal for support and survival but do not kill the host instantly. They are

predator when they prey, kill and eat the second group of insect or animals (preys).

As noted by Vishanbharan (1985), some of the insects generally found in stored food

grains and other agricultural food crops include:

Sitophilus orizae and S, grainarius: These are called rice and granary weevils,

respectively. The adults are recognized by the presence of a snout-like projection or

probosis from the head, and the larvae are white, tiny irregular masses. The two

species (Sitophilus orizae and Sitophilus grainarius) can be distinguished by the

presence of dense round punctures on the thorax in rice weevil and less dense

elongated pits on the thorax of the granary weevil. Both adult and larvae stages are

harmful.

Rhizoperthadominica: This insect is recognized by the cylindrical body with head

bent downward and its slow movement. The larvae are coniform in shape and both the

adult and larvae are destructive to grains.

Tronoderma granarium: The general name to this insect is khapra. The adults have

very short life span. The larvae are many segmented and yellowish brown in colour

with morable erectile hair with the posterior segment forming a tail or a faft of hair.

The larvae are very harmful (Sahay and Singh, 1998).

10 Lasioderma sertcorne: These beetles affect tobacco, cigarette or tumeric, ginger,

and pepper. The adults have yellowish brown colour and hemispheral shape, quite

different from Khapra which have their heads hidden under the downward neck

shield. Both the adult and larvae are harmful. The freshly emerged larvae are very

mobile.

Tribolium castaneum and T.confusion: Their common names are red flower beetles

and confused beetles respectively. They exist everywhere with other insects. The

adults are red in colour with brisk movement. In the red flower insects the segments

of the antennae are smaller at the base and abruptly larger.

Lacmophileus minutes: These are called flat grain beetle and are longer antennae; and

can be seen in association with Oryzaphilus and Tribolium (Ofuya and Lale, 2001).

Bronchus spp: They are commonly known as pulse beetles. The adults are almost

specifically triangular in shape, brownish-grey in colour and covered with tiny

bristles.

Latheticus orizae: They are known as long head flour beetles. The adults are slender,

dorsa ventrally flattened insects, pale yellow in colour. The antennae are seven

segments, club-shaped and small.

Stegodium paniccum: These are commonly called spice beetles. The adults are

cylindrical in shape and brownish in colour. They have long antennae and the last

three segments clubbed at the end as distinct from Lesiodema serticorne (Haines,

1984).

Carcyra cephalonicca. This is a moth which is pale green in colour with an expansive

wing of about 12 to 14mm in diameter. Larvae are creamy white in colour with light

brownish yellow broad head. It is commonly known as rice moth and antennae are not

close over wings when the insect is at rest.

Ephestra coustella. This is commonly known as fig moth or almond moth. It is

greenish in colour with a wingspan of about 20 mm. The larvae are pinkish in colour.

They can be distinguished by the tranverse stripes on the outer wings.

Plodia interpunctella: The common name is Indian meat moth. The adult has wing

expanse of 14 to 20 mm. When at rest with the wind closed, the insect is 8 to 10cm

long and is greyish yellow in colour. Larvae are yellowish white while some are

reddish or even green with brown head.

11 Sitatroga cercaletta: This is commonly known as grain moth. The adult is small,

yellowish brown in colour with a wing expanse of 10 to 14 mm and 6.9 mm long.

Larvae are white in colour with a yellowish head.

2.7 Effects of thermodynamic properties of the environment on pest infestation of stored

grains

The physical conditions of the environment influence the development and behaviour

of stored product pests. Temperature, humidity and light interact to affect the development

and biological activities of stored product pests, and subsequently influence the storage life of

the stored products.

a. Temperature: Temperature influences the reproduction and production of pests in

stored products. As temperature increases the rate of development of individual pests

and their biological activities increase. .All species have optimum temperature at

which they grow faster. However, above the optimum temperature, the rate of

development and activities of individual decrease but mortality rises and the rate of

population falls. All important tropical storage insects have optimum temperature

range of 25 – 300C (Haines, 1991). Appert (1987) noted that the optimum

temperature for most store arthropods and microorganisms was 300C. For these

species, temperature below the range of 18 - 200C usually reduce the rate of

population growth so much that they cause no significant damage. Also temperature

above 450C for just a few minutes will kill most of these organisms. Storage at

extremely low temperature of about below 50C for extended periods will eradicate

most pest species in store.

The main storage problem of food grain in the tropic is its high temperature range at

the arid zone (20 – 400C) and at the humid zone (20 – 350C) throughout the year (De Lima,

1987; Adesuyi, 1997). This high temperature range speeds up the biological activity of

storage pests. The metabolic heat produced by the grain and the pests contribute also to the

temperature range of the product environment. In considering temperature for safe storage

system, the following conditions must be borne in mind:

i. Mites do not develop below 50C nor insects below 150C,

ii. The effect of temperature on an organism can be correlated with the amount of

grain moisture,

iii. Most of the storage fungi do not grow or develop at temperature below 00C.

12b. Humidity: The effect of temperature on biological activity of storage pests

depends very much on the ambient humidity, which varies considerably according to

the region and time of the year. In the sahel region, humidities are as low as 15 –

20% r.h. during the cold season when temperature is as low as 220C and during the

hot season temperature is usually above 350C (Lale, 1998). Under these conditions

the rate of population growth for most pest is slowed down (Kitch et al., 1992; Lale,

1998).

c. Light: Tropical region generally have long day length, but day length is relatively short during the cold season and high in the high attitude regions.

Many insect pests of stored grains are sensitive to photoperiod whereas many

complete their life cycle in the bulk of the commodity where there is no light at

all. Some species like C. Maculatus prefer dark condition for oviposition (Iloba

and Osuji, 1986). Others such as Oryzae philus mercator prefer equal durations

of dark and lightness for oviposition and development (Okiwelu et al., 1998).

3. Effect of biolotic factors on insect infestation of stored grain

Biolotic factors include all the interactions, both positive and negative within all the

living organisms in their environments. These could be seen as predation, parasitism,

pathogenecity, cannibalism and competition.

a. Predation: predators kill and eat other animals known as preys. Preys are usually

smaller than predators. The most efficient predators are obligate specific predators,

which attack only certain species of insects and are adapted to storage insects and

mites. Obligate specific predators can cause considerable damage to the rate of

population growth of stored product pest. Two very common predators are the

Hemiptera (the pirate warehouse bug), Xylocoris flavipes (Reuter) which preys on

eggs and lavae of most stored product species (Arbogast, 1975) and the histerid

beetle, Teratrisosoma migrascens Lewis, which prey on beetles of various families.

The efficiency of any predator largely depends on its ability to move freely through

the food medium, which is not very possible in dense media like flours.

b. Parasitism: the insects widely known as parasitoids are species of parasitic wasps

belonging mainly to three families namely Pteromalidae, Braconidae and Bethylidae

of Hymenopetra (Scholler et al., 1997). Stored product insects are hosts to many

different parasitoids, which in most cases cause the death of the hosts. Depending on

their nutritional ecology parasitoids like predalors are either generalists or specialist

13(Schollar et al., 1997). Important parasitoids of tropical storage include the tiny

wasps of the family trichogrammatidae. These are egg parasitoids of the genus

Trichgramina weswood. Specialist parasitoids parasitize eggs, lavae but rarely adults

of closely related hosts. Dinarmus basatis (Rondam) is a prasitoid of stored product

Bruchidae, especially colloso bruchus spp (Haines, 1991).

c. Pathogens. Stored- product insects are known to be infected by some

microorganisms such as Bacterium bacillus thungiensis, Protozoanse triboliocyetis,

Mattesia, Mosema, Adelina etc. Currently, preparation of B Huringiensis toxin or

insecticidal virus has been effectively applied against moths (McGuaphey, 1995,

1978) and beetles in biological control programmes.

d. Cannibalism: Several species of storage pests are cannibalistic and have

significant effects on population (Haines, 1991). Larvae of primary pests are

cannibalistic when developing in crowded grains and affect larvae of some

Tenebriomidae, family.

e. Competition: Competition occur when two or more individual of the same species

(intraspecific competition) or of different species (inter specific competition) attempt

to exploit the same resources such as food, oviposition site or habitat. Physical factors

also play a decisive role in determining the outcome of competition.

2.8 An overview of pest problems and management in the tropics

The tropics is a region between the tropic of cancer (North of the equator) and the

tropic of capricon (South of the equator) (Humphreys, 1978; Willamson and Payne 1978).

Variations in the interactions of the psychometric parameters including temperature,

humidity, rainfall, solar radiation, pressure and ionization give rise to such subtropical

regions of humid tropics, sub humid tropic and semiarid tropics (Gibbon and Pain, 1985)

Thus within the tropics there is variation in the degree of rainfall, diurnal temperature, solar

energy, radiation and other elements of weather. On the average diurnal temperature, annual

rainfall, solar radiation and air movement are high and very favourable to insect infestation of

food crops both in the field and in store (Haines, 1991).

Pests are feedant organisms that feed and destroy food crops, reducing their quality

and quantity either in the field or in store after harvest; and they include microorganisms,

mites, insects, rodents, and birds. Harvested food crops are not always consumed

immediately after harvest but some are reserved for a period of time before consumption. In

14the tropical environment pest problem may begin in the field once the crop has attained

maturity and is undergoing dehydration (De Lima, 1987). Several stored product pests have

been shown to infest a number of crops in the field prior to harvest (Flamigan, 1978; Appert,

1987; Hagstrum et al., 1996). Therefore, a primary source of pest infestation in storage is

field infestation. Studies have shown that field infestation by stored product insects emanates

from emigrating ones from farmer’s’ silos and stores since infestation decreased with

distance from storage (Hagstrum et al., 1996). Insects are also known to breed in commodity

residues, in farm equipment, vehicles, storage bins, flour mills, warehouses and port storage

facilities. These commodity residues allow insects population to survive during period when

the storage containers are supposed to be empty (Hagstrum and Stanley, 1979).

The degree and nature of grain damage by stored product pests depends on the types

of pests and extent of infestation. Damage to food grains due to stored product pests

manifests in different ways:

1. Reduction in mass. About 10% of the food grain weevils eat up grain during growth

from egg to adult. Three times this amount is eaten away by rodents.

2. Spoilage of grains by heating: Heating up of grains sometimes result from metabolic

activities of the infesting pests, and this cause serious grain damage and also give

room for wider infestation.

3. Reduction in seed germination: Seed grains devored by germ eaters are not likely to

germinate.

4. Contaminated with metabolic waste: Food grains specially the milled products get

contaminated with insect excreta, secretions and dead bodies of insects.

5. Reduction in the food value: The nutritive value is reduced.

6. Development of musty smell and pulvelactic odour.

7. Production of mycotoxins and other toxicants.

In the tropics generally, with Nigeria as reference, pest management of both field and

harvested crops is poorly handled and sometimes overlooked. Appreciable proportions of

grains are lost to pests in store due to lack of knowledge and poor handling. Hence there is

always season of glut and of scarcity for these grains each year.

2.9 Control and management of storage insect pest of grains and flours

Stored grains in the tropics depreciate in quality and quantity with time as a result of

insect infestation. Many food legumes are harvested already infested with pest in the field.

15Some get infested in the store with insect pests harboured in food commodity. Strategies to

reduce post-harvest loses due to insect infestation are varied and will depend on the

morphology of the pest being checked, the type and nature (grain or flour) of commodity

being stored, type of storage container/structure, quantity of commodity being stored and the

duration of the storage (Ofuya and Lale, 2001). Pest control and management of insect pest in

grains could be by preventive or curative measure (Mitsui, 1970) or by direct pest reduction

and indirect supplementary control (De-Lima, 1987). Preventive measures are taken to avoid

infestation at all while curative measures are taken to wipe out any kind of infestation. Very

common preventive measures include:

i. Drying (ii) Cooling by aeration (iii) Low temperature storage (Banks and Fields,

1995) (v) Protective measure storage / packaging. (vi)Use of chemical as grain

protectant, attractant and repellant. (vii) Use of hygienic measure to keep the store

environment clean and hygienic (Compton et al., 1993)

Some common preventive measures include:

Heating at 600C for more than 10 minutes or at 500C for 2 hours;

Exposure of the grain or flour to gama or beta radiation at a short time to kill all the

pests;

Male sterilization by irradiation and continuous release of adult male for one year

completely destroys the population;

Use of centrifugal force to kill all the insects in food flour;

Use of chemicals by spraying, dusting, vaporization and fumigation to kill all insects

and sterilize the food;

Use of biological methods by introducing parasitoid or predator in the stock

(Markham and Herren, 1990).

Fundamental principle and working operation of some of these methods may be necessary

for choice and successful application in use of chemical. Commercial insecticides most

commonly used include organophosphates pirmiphosmethyl, chloropyriphos-methyl,

fenitrothion and melanthion, and the synthetic pyrethroids, deltamethrin and permethrin

which are applied singly or in comination i.e organo phosphates and synthetic pyrethroids

according to manufacturers prescription (Appert, 1987; Singh et al., 1978; Compton et al.,

1993). Insecticides may be applied as aerosol, dust or water based or ultra-low volume spray

(Snelson, 1984)

16 Air-tight storage may involve hermatic sealing of grains in pits, under ground,

semi-underground or in air tight containers. This kills any pest present in the stock

and prevents further infestation. The pests are killed due to hypoxia, hypercarbia or a

combination of both which is created by respiration of the insects and the grains

(Fleural-Lessard, 1990)

Sometimes the threshed grains are stored together with admixture of inert materials in

the cans or bags. Common inert materials used to store grain legumes include clay, diatomite,

woodash, silicate and sand (Wolfson et al., 1991). They reduce insect population in the store

by abrasion causing mortalities of the insects by (De Lima, 1987; Chimoada and Giga 1997).

The most cost effective way of controlling pests is by preventing their infestation in

the first instance. Hence, the need for good management of the farm, harvesting, store and

transportation of the grains from farm to warehouse is important. Some management

practices had been reported:

- Harvested legumes (grains) at the peak of maturity are dried as soon as

possible to avoid pre-harvest infestation to pass to post-harvest infestation

(De-Lima, 1987);

- Mechanical methods should be used for threshing, shelling, sorting and

grading, but must be manual and gentle so as not to damage the grains nor

expose them to more inset havoc. There must be no delay between all these

processing stages;

- Improved storage designs that have no hide out for insects and their larvae

should be used;

- Insect-resistant crop varieties with high yielding should be used for planting

(De-Lima, 1987);

- Farmer should be vigilant and equipped to carry out pest surveillance to

detect on time and control any infestation.

2.10 Use of plant materials and powders for insect control in stored grains.

Plant materials used as insect control agents have broad spectrum in action, are safe to

apply, and easily processed (Talukder and Howse, 1995); and several studies have shown that

they offer good prospects for the protection of stored products against damage by pests

(Nawrot et al., 1986; Sharaby, 1988; Khanam et al., 1990, Serit et al., 1992; Talukder and

Howse, 1994). Some of the plant materials studied include spices, herbs, and their powders

17and extracts which have been shown to have serious effects on insect pests, including those

of stored products (Grainge and Ahmed, 1988; Jacobson, 1989, Shaaya et al., 1991).

Traditionally, plant materials have been mixed with legume pods or seeds in storage to

reduce brunchid attack (Golob and Webley, 1980, Delobel and Malonga, 1987). Many of

such plants used have known medicinal and pharmacological properties to depress

oviposition and projeny emergency of Callosobruchus maculates, deterred adults from mixed

cowpea (Taylor, 1975; Don-Pedro, 1985) and significantly reduced viability of Maculatus

eggs (Rajapakse, 1990). Many other plant materials, including leaves of Bascia sengalensis,

powders from Microtiana tabacum L., Erythrophleum suaveolcus and Ocimum gratissium L

have exhibited some insecticidal effects (Alzouma, 1989; Ofuya, 1990). Waterm root bark is

toxic to adult C. maculatus and protects cow pea seeds from the pest attack (Ogunwolu and

Idowu, 1994; Ogunwolu and Odunlami, 1996). Short time exposure of adult bruchids to Z.

sunthoziloids powder rendered the insects unproductive (Ogunwolu et al., 1998).

These insecticidal plants are applied at the concentration of less than 1g/kg to 20g/kg

of seeds (Lale, 1995). It is evident that plant materials which controlled C. maculatus will

generally control other Collosbruchus species. For example, Rajapakse and Van Emden

(1997) reported that the response of C.maculatus, C. chinensis and C. rhodessianus to control

by plant powder was similar.

However, some researchers (Taylor, 1974; Delobel and Malonga, 1987, Shikaan and

Uvah, 1991) questioned the applicability of plant parts in preventing insect damage in stored

seeds at commercial level because of the high quantity of the plant materials required.

2.11 Use of plant extracts and oils for control of insect pests of stored grains

The use of edible oils as contact insecticide to protect grains, especially legumes

against insect pests has been in practice many centuries ago in Asia and Africa (Jilani et al

1988; Rajapakse and Van Emden, 1997). Many different edible oils have been investigated

for insecticidal effects against stored product insect pests (Verma and Pandey, 1978; Oca et

al., 1978; Pandey et al., 1983, 1986; Missina and Renwick, 1983; Ivbijaro 1984 a; b; Don-

Pedro, 1985; Ahmed et al, 1988;). Extraction of insecticidal plant powders with appropriate

solvent often concentrate the active ingredients and make their potency more effective

(Benner, 1993). Crude ether extracts of monodora myristica is far more effective as legume

seed protectant against C. maculatus infestation than the ground seed (Ofuya et al., 1990).

18Aku et al., (1998) reported that extracts from A. senegalensis root bark were more

effective than the powder in the control of C. maculatus.

Several other workers have shown that plant oils and extracts are more effective than

the whole plant powder in the control of Bruchid damage to legumes (Singh et al., 1978;

Pandey et al., 1981; Missina and Renwick 1983; Pereira, 1983; Jadhav and Jadhav, 1984;

Daniel and Smith, 1994; Rajapaske and Van Emden, 1997). The vegetable oils which have

been shown to have insecticidal effects include oils from African palm, maize (corn),

groundnut, soyabean, cottonseed, neem, mint, saseme, rapeseed, sunflower and mustard.

These vegetable oils are available in the local market and are used by farmers in some

countries eg Nigeria as seed protectants against insect pests (Compton et al., 1993). However,

high concentrations may be needed for effective insect pest control. Peasant farmers may not

be able to afford such large quantity for just protection of their seeds against insect pests.

Also edible oil could be velorized for trade and export. Hence the need for plant oils of higher

volatility and of less commonly used as food commodity, but which must be toxic to adult,

young larvae and eggs of insect pests.

2.12 Lipid oxidation

Oxidation of lipids which occur during storage, processing and heat treatment is one

of the basic processes causing rancidity in food products leading to oxidative deterioration

(Hurdson, 1990). Oxidative deterioration of foods manifest in losses in colour, flavour,

texture and nutritive values of the food. The consequences of lipid oxidation include

decreased nutritional and physiological value of lipids and deterioration of fat-soluble

vitamins and essential fatty acids (Karpinska et al., 2001). Products of lipid oxidation have

also been shown to cause pathological changes in the mucus membrane of the alimentary

tract, inhibit the activity of enzymes and increase the contents of cholesterol and peroxides in

blood system, thus activating the process of atherosclerosis (Gardner, 1979; Karpinska et al.,

2001). Lipid oxidation products can also have carcinogenic activity (Gardner, 1979 Ames,

1983, Jacob, 1995).

Oxidative stability of food is related to the degree of saturation of the lipid fraction;

with the rate of oxidation increasing with the degree of unsaturation. Unless mediated by

other oxidants or enzymes, oxidation proceeds through a free radical chain reaction

mechanism involving three stages namely:

191. Initiation, resulting in formation of free radicals. An unsaturated

hydrocarbon loses a hydrogen to form a radical, and oxygen adds to the double

bond to form a diradical:

i. RH R* + H*

O – O

1

ii. R1-C=C-R2 + O2 R1 – C – C – R2

1 1 1 1

H H H H

2. Propagation, resulting in free radical chain reaction to form peroxy radical

(RO) hydroperoxide (ROOH) and new hydrocarbon radicals (R.)

R + O2 ROO*

ROO* + RH ROOH + R*

The new radical formed contribute to chain reaction by reacting with another

oxygen molecule (O2).

3. Termination, resulting in formation of stable, non-radical products by the

inter-reaction of the free radicals.

R* + R* RR

ROO* + ROO* - ROOR + O2

RO* + R* ROR

ROO* + R* ROOR

2RO* + 2ROO* 2 ROOR + O2

Antioxidants can be added to the food system to suppress the rancidity development.

Oxidation of lipids is accelerated by:

- Energy content in the form of heat and light

- Presence of divalent metal catalyst

- Presence of inherent enzymes in the system

- Oxygen concentration and type of oxygen

202.13 Functions of Antioxidants in foods.

Antioxidants are chemicals which delay the start or slow the rate of lipid oxidation

reaction in food systems. They either inhibit the formation of free alkyl radicals in the

initiation step or interrupt the propagation of the free radical chains. Most antioxidants in use

in food systems are monohydroxy or polyhydroxy phenol compounds with various ring

substitutions (Decker et al., 1992). They need low activation energy to be able to donate

hydrogen to free radicals to form stable complexes. When the hydrogen is donated, the

resulting antioxidant free radical ring cannot initiate another free radical formation because

they are stabilized. There is delocalization of radical election in the antioxidant free radical

ring. The antioxidant free radical ring cannot also undergo rapid oxidation but can react with

lipid free radicals to form stable complex compounds. Thus antioxidants inhibit oxidative

reaction of lipids in food system by either donating hydrogen to free radicals to form stable

compounds or by formation of a complex between the antioxidant radical (ring) and lipid

radicals viz.

1. R* + AH RH + A*

RO* + AH ROH + A*

2. ROO* + AH ROOH + A*

R* + A* RA

RO* + A* ROA, where R*, RO*, ROO* are respectively alkyl,

alkoxy and peroxy radicals from lipid molecules.

AH and A* are antioxidant and antioxidant radical respectively.

Commercial antioxidants in use in food systems are of two categories, synthetic and

natural antioxidants. Generally regarded as safe (GRAS) synthetic antioxidants include

butylated hydroxyl anisole (BHA), butylated hydroxyl toluene (BHT), propyl gallate (PG)

and tertiary butyl hydroxyl quinone (TBHQ). The natural antioxidants in commercial use

include tocopherols (delta > gamma > beta > alpha), nordihydrogurtic acid (NDGA), sesamol

and gossypols.

Application of antioxidants to foods really depends on the nature and composition of

the food system and also on the antioxidant and its composition. Antioxidants are applied to

foods by either mixing the antioxidant to oil or melted fat which is then mixed with the food,

adding the antioxidant in diluent which is then added to the food system, making a solution of

the antioxidant and then spraying to the food system or dipping food into the system. An

ideal antioxidant, whether natural or synthetic, should have the following features:

21- It should not be absorbable by the body and must have no harmful

physiological effect on the consumers;

- It must contribute no objectionable flavour, odour, colour or taste to the food;

- It must be fat soluble and effective at low concentration;

- It must not be affected or destroyed by processing operations.

Other agents including metal chelators, singlet oxygen inhibitors and peroxide

stabilizers also inhibit lipid oxidation.

Metal chelators in use include phosphoric acid, citric acid, ascorbic acid and their

salts and ethylene diamine – tetra – acetate (EDTA). They work by deactivating free trace

metals or metals of salt of fatty acids by forming complex ions or coordinated compounds.

Products from maillard reaction and smoking of meat and fish constitute the singlet oxygen

inhibitors and peroxide stabilizers.

2.14 Natural antioxidants

Antioxidants can be of natural or synthetic origin. Some synthetic antioxidants, such

as BHA and BHT, might be dangerous for living organisms (Attmann et al., 1986). Also

naturally derived antioxidants are perceived by consumers to be better and safer than the

synthetics (Dorko, 1994). Some well – known herbs and spices, which contain antioxidant

substances, are rosemary (Rosmarinus officinalis), sage (Salvia officinalis), garden thyme

(Thymus vulgaris), oregano (Origanum vulgare), Majoram (Origanum majoram), and so

many others (Madsen and Bertelsen, 1995; Ramarathnam et al., 1995).

Ascorbic acid, tocopherol isomers, Carotene and rosemary extracts have been applied

for their antioxidant properties in foods (Chipault et al., 1956, Lee et al., 1995). Tocopherols,

ascorbic acid and β-carotene have been reported as compounds that may protect against

cancer, heart disease and cataracts (Barrak and Langseth, 1994).

2.15 Assessment of antioxidant activity in food system

The effectiveness of an antioxidant in food system can be assessed by measuring the

degree of lipid oxidation of such food over time during storage. Such measurement fall into

the following categories:

1. Measurement of peroxide value (POV) (Asakawa and Matsushita, 1976) using

either iodometry:

22ROOH + 2KI ROH + K2 + K2O, or thiocyanide method: ROOH +

Fe2+ ROH + HO* + Fe 3+

2. Measurement of decomposition products (Asakawa and matsushita, 1980)

using:

- Colorimetry with 2,4 DND derivatives to assay for carbonyl value,

- Colorimetry with thiobarbituric acid to assay for TBA value

- Gass chromatography to assay for the volatile products,

- GC – MS to assay for the volatile products structures.

3. Measurement of oxygen consumption (Riely et al., 1974, Gut et al.,

1988).This is achieved using any of the following methods:

- dissolved oxygen meter,

- weighing method,

- weighing manometer

4. Physicochemical methods of measurement (Gut el al., 1988) by using

- UV absorption technique to measure the degree of double bonds using IR

spectrometry, etc.

2.16 Botany, ecology and distribution of Tamarindus indica Linn

Tamarindus indica is a tree crop originating from African but introduced long ago

into India where it has become more economically established through selection and breeding

(Duke et al., 1981). The tree is a monolypic genus within the caseulpinacaceae subfamily of

legumes (F/FRED, 1992). It is a large tree averaging 20 to 25 meters in height and 1 meter in

diameter. It is an evergreen tree with a wide, spreading crown and a short, stout trunk. It has

fresh green leaves on it all year round. The leaves often form a dense canopy on the branches

all round. There is always abundant leaf falls that cover the underneath from under growth.

The bark is strongly fissured and Silvery grey on the trunk and smooth on the branches.

Leaves are alternate and paripinnate, each with 9 to 12 pairs of small leaflets. The

flowers are small, yellowish with steaks of pink colouration and are clustered in groups of 5

to 10 in drooping racene of 3 to 5cm long. The pods are leguminous in appearance and are

oblong, straight or slightly curved. The pods change from green to dark brown as they ripen

(Purseglove, 1968)

Tamarindus is a pan tropical tree. It thrives well in both semiarid and humid

monsoonal climate. A single tree can produce as much as 50kg of fruits in West Africa where

23annual rainfall is often less than 500mm a year. Tamarind also thrives in humid areas of

Southeast Asia that receive more than 1500mm rainfall annually. Tamarind produces more

fruits when subjected to fairly long, annual dry period (Allen and Allen, 1981; Von Maydell,

1986). It is not tolerant of persistent cold or brief frost. It prefers slightly acid (pH 5.5), deep

alluvial, well drained soils of loamy texture (Von Maydell, 1986). It tolerates a wide range of

physical site characteristics but cannot withstand stagnant inundation, though is often found

on plains and stream banks where frequent flash floods occur. It grows very well in the

savanna belt, particularly along the Guinea Savanna and Sahel Savanna zones. It is always

seen growing on or behind an anthill in the Sahel savanna (Von Maydell, 1986). It also

thrives in the stiff, salty air of coastal areas (Von Maydell, 1986; Von Carlowitz, 1991)

Tamarindus indica, though originated from tropical East Africa- probably

Madagascar, seafaring Arabian traders are thought to have spread the seeds to South Asia. It

is mentioned in Bhuddist sources from 650 AD and in Indian Brahimasamhita scripture

between 1200 and 2000BC (Von Maydell, 1986). Today Tamarind is cultivated in India,

Africa, Southeast Asia, Australia and Southern United States of America (USA). The plant is

propagated by seed. The seed is first soaked in water for about 4 days to soften the hard seed

coat before sowing. This activates the enzymes for germinating before planting. It is planted

about 4cm deep in the nursery bed and is transplanted after about 9 – 10 months, usually

during rainy season. The plant starts flowering between April to May and the fruit ripens

between October and November.

2.17 Chemical composition and uses of the fruits and seeds of

Tamarindus indica Linn

Tamarindus fruit is marketed worldwide in sauces, syrups and processed foods (F/

FRED, 1992). The fruit has sweet sour taste showing that it has some acids and sugars. The

fruits have soft, succulent pulp. Nutrients composition of fruits are about 20.6% water, 3.1%

protein, 0.4% fat, 70.8% carbohydrate (mainly sugars), 3.0% fibre and 2.1% ash,

(Purseglove, 1968). However the seed kernel has protein content ranging from 15.4 to

37.91% depending on the variety and ecological source (Obodo, 1982) Mineral contents vary

significantly in composition from fruit to fruit and varieties across ecological regions.

Minerals detected include sodium, calcium, potassium, phosphorus and iron. Vitamins

include thiamine, riboflavin, niacin and ascorbic acid (Duke et al., 1981; Relwani, 1993). Ega

(1986) reported the amino acid profile to consist of lysine, histidine, arginine, aspartic acid,

24threonine, serine, glutamic acid, proline, alanine cystine, valine, methionine, isoleucine,

tyrosine and phenyl alanine do exist in very small proportions.

Tamarind fruit pulp is used in sauces, syrups, foods, confectionary, curies, preserves,

pickles and beverages (F./FRED, 1992). Once the seeds are extracted and the pods are

removed, tamarind pulp can be stored for several months in compressed form. This practice is

employed in India where tamarind pulps yield averages 250, 000t annually part of which are

exported (Von Maydell, 1986). In Northern Nigeria the fruit pulp is prepared into balls that

are sun dried to harden for future use. The balls are made into drinks in hot water with onions

juice as spice. Also cold infusion of the pulp with sugar or honey in water is allowed to brew

into pleasant acid drink after several days of fermentation. The infusion quenches thirst easily

after muscular work.

Ripe tamarind fruit is widely claimed to have medicinal value. The American

pharmaceutical industry process 100t of tamarind pulp annually (Von Maydell, 1986). The

fruit is said to reduce fever and cure intestinal ailment. It is effective against scurvy and is an

active ingredient in cardial and blood sugar reducing medicines. The pulp is also used as

astringent on skin infections. Young seed contains amber, sweet-tasting oil (about 10 to 15%

by weight (Allen and Allen, 1981). Tamarind oil from the seed has been used in paints and

varnishes and as an illuminant. In India and Southeast Asia, tamarind seeds are crushed and

boiled to produce a paste that is used as a roofing material. This material is highly resistant to

sea water and salt spray corrosion.

2.18 Ecology, botany and distribution of African nutmeg (Monodora

myristica Gaertn)

Morphologically, African nutmeg (Monodora myristica) is a perennial edible plant of

the Annonaceae family. It is a berry that grows wild in evergreen forests of Africa (Burubai,

et al., 2008). It is an ornamental tree of up to 30m high,, with dense foliage and spreading

crown. The stem is fluted, the outer bark is thin, dark brown while the inner bark is light

brown above and pale cream beneath. The stem is aromatic. The leaves are elliptical,

sometimes becoming wider at the apex, about 14 – 15cm long and 5 – 14 cm broad, and

arranged alternately. The plant flowers between September and April, at the time of

appearance of new leaves. The flowers are large, fragrant and pendant, hanging on very long

stalk with a crinkly bract of about 2.5cm long near the end of the stalk. The sepals are about

4cm long, spotted with red and with wavy edges and crisped. There are about 6 petals, with

25the outer ones about 10cm long, brightly yellow in colour and with dark red mark on the

edges. The inner petals are sub triangular in shape, dull cream yellow in colour with red

sports in the inner side.

2.19 Chemical composition and uses of African nutmeg

The fruits are produced, between April and September. They are about 15cm in

diameter, green, round, and usually suspended in large stalk. The pulp is white and contains

numerous seeds. The seeds are composed of moisture (14.7%), protein (9.1%), oil (29.1%),

food energy (458kcal/100g), fibre (25.9%) and ash (2.3%) (Burubai et al., 2008). The seeds

also are rich in potassium, phosphorus, calcium and magnesium.

The seeds yield colourless, volatile oil with a pleasant taste and odour. The seeds are

used as condiments for soups, and are added into snuff as flavouring agent. The seeds are

applied externally to treat migraine, taken orally as a stimulant as stomach cleanser,

caminative and antiparasitic medicine as well as treatment for guninea worm (Agoha, 1974)

2.20 Ecology, botany and distribution of Xylopia aethiopica (Dunal) A. Rich

(Ethiopian pepper).

Xylopium aethiopicum is a perennial edible plant of the Annonaceae family. It is an

evergreen tree plant that grows wild in the lowland rain forest and moist fringe forest of the

savanna zone of Africa (Purseglove, 1968). The tree could be as high as 15 – 25m with dense

foliage forming a canopy. The trunk and stem are smooth, with the outer bark thin and dark –

brown while the inner bark is light brown in colour. The stem is aromatic. The plant flowers

between November and April. The fruits mature between May and July. The flowers occur in

clusters and are fragrant and pendant.

2.21 Chemical composition and uses of Xylopia aethiopica (Dunal A.Rich)

Important constituents of fruits and seeds responsible for their antiseptic properties

include diterpenic acid, xylopic acid and cauranoic acid (Ekong et al., 1969). The pleasant

smelling volatile oil contains pipenes, carene, cyruene, cineole, bisabolane, limonene,

terpinolene, linalool, terpineal, cuminyl, alcohol and cumminic aldehyde (Iwu, 1993).

The fruits are the aromatic part and are peppery, producing stimulating sensation

when chewed. Fruit is used as food condiment and valued for its carminative effects and as

cough remedy. Among the Igbos, soups prepared with the fruits are given to women after

26child-birth as a general tonic and to promote heating, lactation and fertility (Iwu, 1993).

The Yorubas drink a decoction of the fruits as a remedy for stomach ache, dysentery,

bronchitis and biliousness (Iwu, 1993). The seed extract is drunk to eliminate round worm.

2.22 Ecology, botany and distribution of Piper guineense (Schum & Thonn) (African

black pepper).

Piper guineense is a slender climber with weak stem and belong to the family

piperaceae. It is distributed in the high forest zone of the tropical region (Iwu, 1993). It exists

as a secondary forest, occupying forest clearings and underneath of forest trees. It clings on

trunks and remains of trees.

2.23 Uses of Piper guineense (African black pepper)

Constituents of the fruits vary in composition as a result of cultural practices, habitat

and maturity (Iwu, 1993). The fruits and seeds are used as food condiments for flavouring,

and as a component of many local decoctions. The roots, fruits and leaves are incorporated in

preparations for treatment of many infectious diseases such as gonorrhea, bronchitis, and

syphilis (Iwu, 1993). Leaf extract is applied to wounds for healing and is used to regulate

menstrual cycle and remedy fertility in women. Fruit extract is used as a stimulant, a counter-

irritant and as a cough remedy or for gripping stomach ache. Oil from the fruit is used for

perfume and soap-making.