0

POTENTIALS OF Piper guineence (Schum and Thom) AND Mondora

myristica (Gaertn) FOR THE PROTECTION OF STORED MAIZE (Zea

mays) AGAINST Sitophilus Zeamais

BY

NWOSU, ADAORA N.

PG / PGD/ 08 / 48474

DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY

UNIVERSITY OF NIGERIA NSUKKA

DECEMBER, 2010.

i

TITLE PAGE

POTENTIALS OF Piper guineence (Schum and Thom) AND Mondora

myristica (Gaertn) FOR THE PROTECTION OF STORED MAIZE (Zea

mays) AGAINST Sitophilus Zeamais

BY

NWOSU, ADAORA N.

PG / PGD/ 08 / 48474

DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY

UNIVERSITY OF NIGERIA NSUKKA

SUPERVISOR: DR. (MRS.) J.C. ANI

DECEMBER, 2010.

ii

CERTIFICATION

NWOSU, ADAORA N. 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 Post Graduate Diploma (PGD) in Food Science and

Technology. The work embodied in this project report is original and has not been submitted in

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

Dr. (Mrs.) J. C. Ani Date

Supervisor

Dr. ( Mrs.) J. C. Ani Date

Head of Department

iii

DEDICATION

This work is dedicated to my beloved parents Mr. and Mrs. C. B. O. Nwosu.

May God Almighty reward you for me.

iv

ACKNOWLEDGEMENT

I whole heartedly express my profound gratitude to the pillar that holds my life, who by

his grace enabled me to do this work to this point. I also acknowledge all the efforts of my

supervisor, Dr. (Mrs.) J.C. Ani who painstakingly saw to the success of this project despite all

odds. I am very grateful.

I owe a great depth of gratitude to all my lecturers, especially Prof. T. M. Okonkwo and

Mrs I.E. Nwaoha for their valuable contributions towards the success of this project. I appreciate

you all. My deep affection goes to my class mates Loveth, and Obum for your understanding

throughout our stay, and also to Margreth for all your extra input May God in his infinite mercies

reward you.

My inestimable appreciation goes to my parents Mr. and Mrs. C.B.O. Nwosu and my

beloved brothers Okwudili and family, Chidubem, Ikenna and family and Ugochukwu and to

my cousin Chiedozie, whose love and support sustained me throughout the period of this

programme.

As long as I remain a living entity, I am indebted to you all.

NWOSU, ADAORA N.

v

TABLE OF CONTENTS

Title page - - - - - - - - - i

Certification - - - - - - - - - ii

Dedication - - - - - - - - - iii

Acknowledgement - - - - - - - - iv

Table of content - - - - - - - - v

List of Tables - - - - - - - - - vi

List of Figures - - - - - - - - - vii

Appendices - - - - - - - - - viii

Abstract - - - - - - - - - ix

CHAPTER ONE: INTRODUCTION

1.1 Cereals - - - - - - - - - 1

1.2 General Objective - - - - - - - 3

1.3 Specific Objectives - - - - - - - 3

1.4 Justification for the Study - - - - - - - 4

CHAPTER TWO: LITERATURE REVIEW

2.1 World Maize Production - - - - - - 5

2.2 Maize and the Developing World - - - - - 6

2.3 Maize Storage - - - - - - - - 8

2.4 Chemical Composition - - - - - - - 10

2.4.1 Carbohydrate - - - - - - - - 10

2.4.2 Protein - - - - - - - - - 10

2.4.3 Lipids and Related Compounds - - - - - - 10

2.4.4 Minerals - - - - - - - - - 11

2.4.5 Vitamins - - - - - - - - 11

2.4.6 Pigments - - - - - - - - - 11

2.5 Uses of Maize - - - - - - - - 12

2.6 Post harvest Losses in Maize - - - - - - 13

vi

2.7 The Maize Weevil - - - - - - - 14

2.7.1 Ecology - - - - - - - - - 14

2.7.2 Damage - - - - - - - - - 14

2.7.3 Life History - - - - - - - - 14

2.8 Harmful Effects of Synthetic Pesticides - - - - 15

2.9 Higher Plant Products as Alternatives to Synthetic Pesticides - - 17

2.9.1 Monodora myristica - - - - - - - 18

2.9.2 Piper guineense - - - - - - - - 19

CHAPTER THREE: MATERIALS AND METHODS

3.1 Materials - - - - - - - - - 20

3.2 Preparation of Samples - - - - - - - 20

3.3 Culturing of Weevil - - - - - - - 20

3.4 Preparation of Spices - - - - - - - 20

3.5 Storage of Maize - - - - - - - 20

3.6 Proximate Analysis - - - - - - - 21

3.6.1 Determination of Moisture Content - - - - - 21

3.6.2 Determination of Ash Content - - - - - - 22

3.6.3 Determination of Crude Protein - - - - - - 22

3.6.4 Fat Determination - - - - - - - 23

3.6.5 Crude Fibre Determination - - - - - - 24

3.7 Damage Assessment - - - - - - - 25

3.8 Seed Viability - - - - - - - - 25

3.9 Production of Maize Products - - - - - - 26

3.9.1 Production of Fermented Maize Product - - - - 26

3.9.2 Toasted Corn Production - - - - - - 27

3.10 Sensory Evaluation - - - - - - - 27

3.11 Statistical Analysis - - - - - - - 28

CHAPTER FOUR: RESULTS AND DISCUSSION

4.1 Proximate Composition of Untreated Maize sample before Storage - 29

4.2 Effect of Spice Treatment and Storage Time on Protein Content of Maize- 33

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4.2.1 Effect of Concentration of Monodora myristica and Storage

Time on Protein content of maize - - - - - 34

4.2.2 Effect of Concentration of Piper guineense and Storage time on Protein

Content of Maize - - - - - - - 36

4.3 Effect of Spice Treatment on Seed Viability after Storage - - 37

4.4 Effect of Spice Treatment on Damage of Maize by Weevil during Storage 38

4.5 Sensory Quality of Products from Spice Treated stored Maize - - 40

4.5.1 Sensory scores of Pap Produced from spice Treated stored

Maize Sample - - - - - - - - 40

4.5.2 Sensory Scores of Toasted Corn Produced from Spice Treated

Stored Maize Samples - - - - - - 42

CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS

5.1 Conclusion - - - - - - - - 44

5.2 Recommendation - - - - - - - 45

REFERENCES - - - - - - - - 46

APPENDICES - - - - - - - - 50

viii

LIST OF FIGURES

Figure 1: Flow diagram for pap production

Figure 2: Flow diagram for toasted corn production

Figure 3: Effects of concentration of Monodora myristica and storage time on protein

content of maize

Figure 4: Effects of concentration of Piper guineense and storage time on protein

content of maize

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LIST OF TABLES

Table 1: Top ten Maize Producers in 2009

Table2: proximate composition of untreated maize before storage

Table 3: Proximate composition of maize treated with different concentrations of

Monodora myristica and Piper guineense at the

end of storage period of one month

Table 4: Effect of spice treatment on seed viability after storage

Table 5: Effect of spice treatment on damage of maize by weevils after storage

Table 6: Sensory scores of pap produced from spice treated, stored maize

Table 7: Sensory scores of toasted corn produced from spice treated, stored maize

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ABSTRACT

Undamaged and uninfested maize grains were hand picked, packaged in moisture proof

package and disinfested in the deep freezer for 96 hours. Thirty six sets (500g per set) of

disinfested maize were weighed into prepared containers. Each set of maize was infested with

200 live maize weevils (Sitophilus zeamais). The weevils were reared on whole maize at room

temperature inside a plastic bucket covered with muslin cloth. Graded levels (0 to 10%) of

coarsely ground spices Monodora myristica and Piper guineense were introduced into the

infested maize samples. The content was mixed and covered with cotton material held in place

with rubber bands. Contents were stored for a period of one month. Protein content of the stored

samples was monitored weekly. Results show that significant differences (P<0.05) existed

between samples. After storage treated samples were analysed for the effect of the spices on seed

viability and extent of damage done by the weevils. Results show that Piper guineense offered

more protection to the maize grains than Monodora myristica. Significant differences (P<0.05)

existed amongst the spice treated samples and the control. Effect of the spice treatment on the

acceptability of the products made from the spice treated maize was assessed subjectively using

two products namely fermented maize gruel, pap (akamu) and toasted corn. Products were

scored for colour, taste, flavour and general acceptability by a 20 member untrained panel, using

a 5 - point hedonic scale, where 5 represents the most desirable attribute (very desirable) and 1

represents the least desirable attribute (very undesirable). The result of sensory evaluation

revealed that treatment did not affect the colour of the products, since there were no significant

differences in colour (P>0.05) between samples. There were significant differences (P<0.05) in

flavour, taste and general acceptability. The control and the sample treated with 2%

concentrations of Monodora myristica received the highest panel scores on taste, flavour and

general acceptability.

1

CHAPTER ONE

INTRODUCTION

1.1 Cereals

Cereals are monocotyledons belonging to various tribes of the grass family and they

constitute various crops which serve as industrial raw materials and staple foods the world over.

World cultivated cereals include wheat, maize, rice, barley, oat, rye sorghum, millet, among

others. Some of the important characteristics of cereals include the following, high

carbohydrate, low fat, and a fair content of protein. The functionality of these components in the

different cereals determines, to a large extent, their uses as food and industrial raw materials.

(Enwere, 1998).

Structurally, there are a few important features that cereals have in common and these

form the basis for subsequent milling and processing operations. All cereals are plant seeds and

as such contain a large centrally located starchy endosperm which is also rich in protein, a

protective outer coat consisting of two or three layers of fibrous tissue, and an embryo or germ

usually located near the bottom of the seed (Ihekoronye and Ngoddy, 1985).

Cereals have an easy-to-preserve advantage over other plant crops, in their being able to

dry to a safe moisture level naturally in the field. In humid environments, cereals can be dried

by artificial means. For the safe storage of cereal, the following conditions need to be

implemented.

(1) Grains must be dried to an appropriate moisture content within a reasonable period for

safe storage.

(2) Grains, once dried to a safe moisture level must be protected from excessive moisture

generation and uptake.

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(3) Grains for storage must be made free of insect pests by pre-storage chemical or physical

treatment followed by insect proofing to suppress insect proliferation or attack (Okaka

2005).

Cereals are generally referred to as grains due to their granular nature.

Maize (Zea mays) originated in the Western hemisphere, but is now cultivated in many parts of

Africa, North, South, and Central America, Europe and Asia (Matz 1969, Obi 1991). According

to Purseglove (1992) there are different varieties of maize examples include pod corn, popcorn,

flour or soft maize, sweet corn or sweet maize, waxy maize, flint maize and dent maize. The last

two are also known as field corn or maize..

Spices have been defined by the Food and Drug Administration as aromatic vegetable

substances used for the seasoning of food, and from them, no portion of any volatile oil or other

flavouring portion has been removed, and are free from artificial colouring matter, adulterants

and impurities. (Enwere,1998).

Spices add flavour to foods. They consist of rhizomes, barks, leaves, roots, flowers,

fruits, seeds and other parts of a plant (Parry, 1969). Most are fragrant, aromatic and pungent.

The flavouring agent in spices constitute only a small fraction of the dry matter. The bulk of the

materials consists of carbohydrates, such as cellulose, starch, sugars, pentosans and mucilages.

Spices also contain proteins, tannins, resins, pigments, mineral matter, volatile oils, terpenes,

alcohols, sesquiterpenoids, esters, aldehydes, ketones, phenols, ethers among others. These and

other compounds vary in different spices and flavouring agents (Enwere, 1998).

Published research on the use of plant materials, extracts and oils for the control of stored

products pests show that over the past 12 years, a large number of plant species from a wide

range of families have been evaluated. Jacobson, (1989), suggested that the most promising

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botanicals were to be found in the families Meliaceae, Rutaceae, Piperaceae, Annonaceae,

Asteraceae, Labiatae and Canellaceae.

Insecticidal evaluation of some plant materials as grain protectants shows that

Aristolochia ringines and Zanthoxylum xanthoxyloides were potent within 1-4 days of treatment.

(Arannilewa and Odeyemi, 2007),

Ohazurike et al., (2006) reported that the efficacy of seed extracts of Jatropha curcas as

maize grain protectants against storage pest Sitophilus zeamais, was dose dependent with higher

doses providing greater protection for the maize grains. Xylopia aethiopica was shown to have

good potential for short term cowpea storage.(Ojimelukwe and Okoronkwo,1999). Udo, (2005)

evaluated the potential of some local spices as stored grain protectants against maize weevil, and

reported that the spices showed good potentials as grain protectants. Among the spices used were

Allium sativum, Piper guineense, Afromomum melequata, Tetrapleura tetraptera, and Xylopia

aethiopica. Also Orji et al., (1991), reported the insecticidal activity of dried fruits of Xylopia

aethiopica and Piper guineense on stored maize.

1.2 GENERAL OBJECTIVE

This study was designed to ascertain the efficacy of two local spices, namely Piper

guineense and Monodora myristica in protecting stored maize.

1.3 SPECIFIC OBJECTIVES

(1) To identify the most effective spice concentration.

(2) To determine the effect of these spices on seed viability after storage.

(3) To evaluate the effect of the spices on the sensory properties of maize and its products.

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1.4 JUSTIFICATION FOR THE STUDY

There is the need for farmers in the rural areas to use affordable materials for the control

of pests, since the use of synthetic fumigants is expensive.

The use of spices will eliminate the serious health problems due to the accumulation of

toxic residues on food grains consumed by human beings.

The farmers will have access to their grains even after a short time of storage, since with

the use of some fumigants the grains must be stored for at least three months before

consumption.

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CHAPTER TWO

LITERATURE REVIEW

2.1 WORLD MAIZE PRODUCTION

The land area planted with maize increased from 105 million hectares in 1961 to about

127 million hectares in 1987. Significant increases in production resulted from more efficient

technological field practices and fertilizer applications, as well as from the introduction of new,

more highly reproductive varieties.

The developing countries have more area given to maize cultivation than developed

countries, but yield per hectare in developed countries is about four times higher since

1961.Yields in the United States for example, have increased significantly, while yields in

Mexico, Guatemala and Nigeria (selected as countries where maize intake by human population

is high), have increased only slightly. While most of the production in developing countries is for

human consumption, in the developed world it is mainly for industrial use and animal feed.

The United States, out produces countries such as Mexico where maize is the most

important staple grain. With changing rural-to-urban populations and lifestyles in developing

countries, there is a continuous shift to the consumption of wheat, which may influence maize

production. (FAO, 1988).

In 2009, over 159 million hectares of maize were planted worldwide, with a yield of over

5 tonnes per hectare.

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Table 1: Top ten maize producers in 2009

COUNTRY PRODUCTION (tons)

United States 333,010,910

Asia 233,633,476

China 163,118,097

Europe 83,958,488

Africa 56,685,857

Brazil 51,232,447

Mexico 20,202,600

Indonesia 17,629,740

India 17,300,000

France 15,299,900

Source : Food and Agricultural Organisation of United Nations Economic

And Social Department; The Statistical Division (2009).

In 2010 the corn planted area for all purpose in the United States was estimated at 35 million

hectares following an increasing trend since 2008.

2.2 MAIZE AND THE DEVELOPING WORLD

Maize contributes 42 million tons of protein a year, which represents 15% of world

annual production of food crop protein. It also represents 19% of worlds food calories (NAS,

1988).

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In many areas of the developing world, maize is a vital staple, particularly for the rural

poor. It spread quickly and widely among poor countries because it is highly adaptable to a wide

range of environments and because of its many valuable properties, stated as follows

It gives one of the highest yields per hour of labour spent.

It provides nutrients in a compact form.

It is easily transportable.

The husks protect it against birds and rain.

It is easy to harvest and can be shelled by hand.

It stores well if properly dried.

Competes with weeds better than other cereals. Etc.

As a result of these benefits, maize has become a favorite crop with farmers in many

developing countries. It is the staple of at least 200 million people in Brazil, El Salvador,

Ecuador, Guatemala, Haiti, Honduras, Mexico, Nicaragua, Paraguay, Ghana, Nigeria, South

Africa etc. Maize is also an important food crop in the Mediterranean region, the Middle East,

and parts of Asia. (Enwere, 1998).

A comparison of the available data on wheat, maize and rice put maize as the second

most important cereal, after wheat and before rice. In terms of yield per hectare, however, maize

out yields the other two, (FAO, 1988). By far the greatest production of maize is field corn of the

dent and flint types. The kernel of the dent maize is hard but not as hard as the flint maize.

The term maize is derived from the Spanish form of the indigenous Taino word for the

plant, maize. This was the form most commonly heard in the United Kingdom. In the United

States and Canada the usual term is “corn”. This was originally the English term for any grain,

but now usually refers to maize. Having been shortened from the term “Indian corn”. Indian

8

corn is currently often used in the US and Canada to refer specifically to multicoloured “field

corn” cultivars.

In scientific and formal usage, “maize” is normally used in a global context but, in bulk

trading contexts, “corn” is used most. In the UK, Australia and other English-speaking countries,

“corn” is often used in culinary contexts, particularly in naming products such as popcorn and

corn flakes, but “maize” is used in agriculture and science.

(http://www.en.wikipedia.org/wiki/maize).

2.3 MAIZE STORAGE

Over the years several storage techniques have been employed for both short-term and long-

term storage of maize, some of which include the following

(1). Sacks: In this method the producer stores the grains in sacks for some time before they are

sold. During this period, precautions have to be taken to ensure the safety of the grain and

to maintain its quality. At least the bagged grains must be kept off the ground to prevent

moisture uptake, and if there is a risk of damage by rodents or other animals, high

platforms fitted with rodent barriers are used.

(2). Metal or Plastic drums: Drums are often used as domestic storage containers. Plastic drums

are used intact or the upper part are cut off to facilitate loading and unloading. If the lid is

tight fitting and the drum is completely filled with grain, any insects present will use up the

oxygen in the drum and die. Metal drums can be adapted for domestic grains storage in a

similar way. Metal drums can also be made air tight inaccessible to rodents, efficient

against insects, sealed against entry of water, drums make excellent grain containers.

However, they need to be protected from direct sunshine and other sources of heat to avoid

condensation.

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(3). Metal silos: Economically valid for storing large quantities of grains, (over 25 tonnes),

metal silos are often regarded as too costly for small scale storage. Nevertheless small

metal silos of 0.4 to 10 tonne capacity has been produced and used, at farm or village level

in developing countries.

(4). Jars: These are large clay receptacles whose shape and capacity vary from place to place.

The upper part is narrow and closed with a flat stone or a clay lid, which is sealed in

position with clay or other suitable material. They are generally kept in dwellings, so that

they may remain in good serviceable condition, not exposed to sun, not porous or cracked.

Proper storage temperature and moisture content control are important for preventing the

growth of moulds and rapid multiplication of insects. Even when these storage moisture and

temperature conditions are optimized, insect and rodent control measures must be instituted so

that all other inputs in storage of produce do not become a wasted effort. Insect pests can cause

damage in many ways including boring of holes on the maize grains. A common pest of the

maize grain is the Sitophilus zeamais commonly known as the maize weevil (Okaka, 2005).

Local spices are used in much location for the purpose of imparting desirable flavour to

foods. A study by Ndukwu and Ben- Nwadibia (2009) showed that local spices have varying

therapeutic applications by local communities. Their uses include acting as stimulants,

expectorants, purgatives, anticonvulsant, and sedatives in the treatment of diarrhea, malaria,

rheumatism, asthma, bronchitis and catarrh.

It was reported that the indigenous people value the plants more for their medicinal uses

than for spicing food. For instance, ginger is more valued for its use in the treatment of coughs,

asthma, cold and hypertension, than as condiments. Ginger is also used for the treatment of

toothache, congested nostrils, piles and hepatitis among others. Also the African nutmeg is used

10

as a stomach cleanser, the powders are used to treat guinea worm, the seeds are used to treat

migraine by applying externally on the forehead (Agoha, 1974). These wide range medicinal

uses however do not obviate the need to test if materials derived from these spices are to be

promoted for use as food protectants.

2.4 CHEMICAL COMPOSITION

The composition of different varieties of maize differ to some extent, with respect to their

carbohydrate, protein, fat, fibre, ash, and vitamins (Enwere, 1998). Different parts of the maize

grain also differ in composition. The flint and dent maize varieties have similar compositions.

2.4.1 Carbohydrate

The carbohydrates and related compounds found in maize are mainly starch, cellulose

and pentoglycan in the cell wall. In addition, maize kernels contain 0.1 to 0.3% raffinose, 0.9 to

1.9% sucrose, 0.2 to 0.5% glucose, 0.1 to 0.4% fructose and smaller amounts of myo-inositol and

glycerol. Maltose and other sugars may appear during germination while raffinose disappears.

2.4.2 Protein

Most of the nitrogen in maize is present as proteins. The predominant protein in maize is

zein, and it is soluble in dilute alcohols. Zein is found mostly in the endosperm. Lysine is the

first limiting amino acid in maize followed by tryptophan. Germ protein usually accounts for

about 15 to 25% of the total protein of maize and may contribute about 25 to 40% of the total

kernel lysine. The total protein of maize grain ranges between 6 to 15%.

2.4. 3 Lipids and related compounds

Lipids in maize vary between 1.2% and 5.7% depending on the variety. Varieties

developed particularly for high oil content are known to yield as much as 14% oil. Among the

11

fatty acids reported to occur in maize lipid are linoleic, (56%), oleic (30%), linolenic (0.7%),

small quantities of stearic, palmitic, and arachidic acids.

Fat soluble substances such as tocopherols (vitamin E) (0.03 to 0.33%) phosphatides

(1%), with lecithin accounting for about 0.5%, beta- sitosterol occur in maize lipids to a minor

extent.

2.4.4 Minerals

Maize contains many minerals such as sodium, potassium, copper, calcium, phosphorus

and magnesium. Most of the phosphorus is present as phytin and nearly all the phytin is in the

germ (Enwere, 1998). Maize has low calcium content of less than 6.00mg/100g, sodium

50.00mg/100g, iron 2.50mg/100g, magnesium 160.00mg/100g, potassium 400.00mg/100g,

phosphorus 300.00mg/100g and sulphur 140.00mg/100g. (Ihekoronye, and Ngoddy, 1985).

2.4.5 Vitamins

Maize is rich in many vitamins. These include B-vitamins such as thiamin, riboflavin,

panthothenic acid, vitamin E (tocopherol), and carotene precursor of vitamin A. The vitamins are

concentrated in the germ. Maize contains niacin but most of it occur in a bound form as niacytin

which is biologically unavailable, and renders maize deficient in niacin. (Ihekoronye and

Ngoddy, 1985).

2.4.6 Pigments

Carotenoids which impart yellow colour to maize grain are abundant in the yellow maize

but not in the white ones. The carotenoids present include carotenes and xanthophylls. The levels

of carotenoids vary in different parts of maize kernel.

12

2.5 USES OF MAIZE

Maize has three possible uses: as food, as feed for livestock, and as raw material for

industry. As a food, the whole grain, either mature or immature, may be used. The maize may be

processed by dry milling techniques to give a relatively large number of intermediary products,

such as maize grits of different particle sizes, maize meal, maize flour, and flaking grits. These

materials in turn have great number of application in a large variety of foods. Maize grown in

subsistence agriculture has continued to be used as a basic food crop. The by-products of dry

milling include the germ which is used as a source of high quality edible oil. In Africa, the most

common method of eating maize is to boil the meal with water until it forms a thick mush or

dough called tuwo. It is also often cooked in more dilute forms to produce pap, porridge, soup,

and even beer. In roasted form,(corn-on-the-cob), it is eaten by most African people with pear,

coconut, or palm kernel. (Ihekoronye and Ngoddy, 1985)

In developed countries more than 60% of the production is used in compounded feeds for

poultry, pigs and ruminant animals. In recent years, in developing countries where maize is a

staple food, more of it has been used as animal feed ingredient.

Wet milling of maize is usually carried out to produce starch with by-products such as

bran, germ and protein concentrate (gluten). The traditional wet milling of maize generally

involves steeping grains to about 45 percent moisture content and then grinding such grains. In

Nigeria for example, the wet milling of maize is more geared towards the production of foods

such as “ogi” and the alcoholic beverages, burukutu and pito.

13

Maize is also the major ingredient used industrially to produce corn flakes and golden

morn, and some commercial weaning foods such as, Babeena, Cerelac, Nutrend etc. Starch from

maize can also be made into plastics and adhesives.(http//www.en.wikipedia.org/wiki/maize)

Stigmas from female maize flowers, known popularly as corn silk, are sold as herbal

supplements. Maize cobs are also used as a source of biomass fuel. Maize is a source of cooking

oil (corn oil). Maize starch can be hydrolyzed and enzymatically treated to produce syrups,

particularly high fructose corn syrup, (a sweetener). Maize meal is also a significant ingredient of

some commercial animal food products, such as dog food.

The corn steep liquor, a watery product of maize wet milling process, is widely used in

the biochemical industry and in research as a culture medium to grow many kinds of

microorganisms (Liggett et al., 1948).

2.6 POST HARVEST LOSSES IN MAIZE

In developing countries agriculture is the driving force for broad based

economic growth. One of the major problems with agriculture in recent times is demand. The

production of more in order to provide food for the population. In realizing this one of the

stumbling blocks seems to be the yield losses due to pests. One of the most important constraints

of having every day sufficient food is the post harvest preservation of its quality and quantity.

During storage food grains and products are severely destroyed by insects and other pests.

In spite of the use of all available means of plant protection, about one third of the yearly

harvest of the world is destroyed by pests. Losses at times are so severe so as to lead to famine in

large areas in many countries of the world. There is need to give priority to post harvest studies,

particularly in the tropics where at least half of the food supply may be lost between harvest and

consumption. In Africa where subsistence grain production supports the livelihood of majority of

14

the population, grain loss caused by storage pests such as the maize weevil threatens food

security. Reduction of insect damage in stored grains is a serious problem in developing

countries due to favourable climatic conditions and poor storage structures (Bekele et al., 1997).

2.7 THE MAIZE WEEVIL

The maize weevil is of the phylum Arthropoda, which is the largest phylum in the animal

kingdom, it is of the class Hexapoda, order Coleoptera and family Curculionidae.

2.7.1 Ecology

The maize weevil is distributed in tropical environments. However, it is becoming

established in temperate environments. In Canada, it is reported in Ontario and Quebec. The

maize weevil is commonly associated with feeding on corn, rice and on other raw or processed

cereals. It infests standing crops before the harvest. It is the dominant Sitophilus species in

tropical subsistence agricultural systems. The maize weevil is closely related to the rice weevil.

2.7.2 Damage

Damage is distinctive. Maize weevil causes damage similar to that of rice weevil. The

larva feeds within the kernel and consumes the endosperm. The adult leaves a large, ragged exit

hole in the kernel and feeds on damaged kernels. The adult maize weevil gathers and reproduces

in stored grains. This produces heat and moisture which can lead to mould development and

invasion by other insect species.

2.7.3 Life History

15

The adult is small about 2.5 to 4mm long. It is dark brown, has a distinctive long snout

and elbowed antennae. It has four distinct reddish patches on the elytra. It can fly. Breeding

conditions are temperatures between 15 and 34°C and 40% relative humidity.

The female lays most eggs within the first 4 weeks after it emerges. It lays one egg on

each grain. The female chews a small hole in the grain to lay the egg and covers it with a waxy

secretion. It lays approximately 150 eggs in its lifetime.

The larva is white, grub-like and legless. It develops and pupates in the kernel. Under

optimal temperature conditions between 27 and 31°C, the maize weevil’s life cycle takes 5 to 8

weeks to complete. Development stops if temperature falls below 17°C. Once the adult emerges

from the kernel, it mates and lays eggs immediately. http://www.grainscanada.gc.ca/storage.

Dusting and fumigation can be used in the store to kill carry over insects and to keep off

insect invasion. Control of insects can be by use of pesticide as dust or spray applied directly on

the grain. Although several methods have been developed as a part of an integrated pest

management (IPM) strategy, at present the control of sitophilus zea mais in Africa relies on the

fumigation of stores using methyl bromide and phosphine. The use of synthetic pesticides poses

a substantial risk to the environment in the form of toxicity to non target organisms and even

human beings. (Ukeh et al., 2008).

2.8 HARMFUL EFFECTS OF SYNTHETIC PESTICIDES

Insect pest control in stored food products relies heavily on the use of gaseous fumigants

and residual contact insecticides. The implications of these are serious problems of toxic

residues, health and environmental hazards, development of insect strains resistant to

insecticides, increased cost of application and erratic supply in developing countries due to

foreign exchange constraints (Obeng-ofori et al., 1997).

16

The current methods for managing stored grain pests depend heavily on synthetic

pesticides. However repeated use of certain chemicals in packing houses has led to the

appearance of fungicide resistant populations of storage pathogens. In recent years there has been

considerable pressure by consumers to reduce or eliminate chemical fungicides in foods. The use

of synthetic chemicals to control post harvest biodeterioration has been restricted due to their

carcinogenicity, high and acute residual toxicity, environmental pollution and their adverse

effects on food and side effects on humans (Brent and Hollomon, 1998; Dubey et al., 2007;

Kumar et al., 2007). The use of synthetic chemicals as anti microbials for the management of

plant pathogens has undoubtedly increased crop protection but with some deterioration of

environmental quality and human health (Cutler and Cutler, 1999). Their uninterrupted and

indiscriminate use has not only led to the development of resistant strains and accumulation of

toxic residues on food grains used for human consumption has also led to serious health

problems (Sharma and Meshram, 2006).

Another method is the use of synthetic fumigants, which has also led to increased cost of

application, pest resistance, lethal effects on non target organisms and toxicity to users

(Okonkwo and Okoye, 1996).

There are three types of harmful effects of pesticides: acute effects, delayed effects, and

allergic effects. Acute effects are injuries or illnesses that appear immediately after exposure.

The effects are usually obvious and reversible if appropriate medical care is given right away.

Delayed effects are illnesses or injuries that do not appear immediately, such as cancer.

Pesticides have been known to cause lymphoma, leukemia, breast cancer, asthma, and other

immune system disorders. Food safety is receiving increased attention worldwide as the

important links between food and health are increasingly recognized. Improving food safety is an

17

important element of improving food security which exists when population have access to

sufficient and healthy food

The increasing concern over the level of pesticide residues in food has encouraged

researchers to look for alternatives to synthetic pesticides. In the context of agricultural pest

management, botanical pesticides play a great role in the post harvest protection of food products

in developing countries. (Dubey et. al., 2008). This has led to the use of spices as grain

protectants.

2.9 HIGHER PLANT PRODUCTS AS ALTERNATIVES TO SYNTHETIC

PESTICIDES

Recently, in different parts of the world attention has been paid towards exploitation of

plant products as novel substances in plant protection. During the past few decades, interest in

the use of plant products increased greatly (Subramanyam and Roesli, 2000). Many tropical

medicinal plants and spices have been used as pest control agents (Lale, 1992). Peasant farmers

and researchers often claim successful use of plant materials in insect pest control including ash

(Ajayi et al., 1987), vegetable oils (Sahayaraj, 2008) and powders of plant parts (Lajide et al.,

1998). Numerous studies have documented the antifungal (Mishra and Dubey, 1994, Elgayyar et

al., 2001 Suhr and Nielson, 2003) and antibacterial (Canillac and Mourey, 2001) effects of plant

essential oils. Examination of indigenous local herbs and plant materials have also been reported

from around the world example, India (Ahmad and Beg, 2001), Australia (Cox et al., 1998).

Higher plants contain a wide spectrum of secondary metabolites such as phenols, flavonoids,

quinines, tannins and essential oils. Such plant derived chemicals may be exploited for their

different properties. And they do not leave harmful residues.

18

Resource poor farmers in developing countries use different plant materials to protect

stored grains against pest infestation by mixing grains with protectants made up of plant

products.

2.9.1 Monodora myristica

Monodora myristica, commonly known as calabash nutmeg, ehuru, Jamaican nutmeg,

nuscade de calabash, ariwo, airama, African nutmeg and African orchid nutmeg is a tropical

shrub of the Annonaceae or custard apple family of flowering plants. The flowers look very

much like those of an orchid, hence the common name “African orchid nutmeg”, and the fruit is

a nearly spherical drupe about the same size as an orange.

The fruit contains a number of these aromatic seeds embedded in a yellow pulp. The

seeds and their seed coat are removed and dried giving a heart shaped spice some 3cm long and

2cm in diameter at its widest part. Once dried these seeds have an aroma reminiscent of nutmeg.

(http://en.wikipedia.org/wiki/Monodora_myristica)

An analysis carried out by Burubai et al., (2007), on the proximate composition of

Monodora myristica reveals that the seeds contain moisture (14.7%), protein (9.1%), oil (29.1%),

food energy (458kcal/100g), fibre (25.9%), ash (2.3%), and acidity (8.3%). In the same vain,

mineralogical analysis using an inductively coupled plasma atomic emission spectrometer, was

conducted. The result revealed that potassium, phosphorus, calcium and magnesium were the

predominant elements in the seeds.

According to Koudou et al., (2007), the composition of the essential oil from the seeds of

Monodora myristica studied by capillary gas chromatography, using a combination of retention

indices and combined Gas Chromatography/Mass Spectrometry (GC/MS) revealed the presence

of 30 components. The oil contains mainly monoterpenoids (93.2%) out of which 77.4% are

19

monoterpene hydrocarbons and some sesquiterpenoids (5.8%). The study suggests that the

presence of these essential oils could contribute to the anti hypertensive activity of Monodora

myristica.

2.9.2 Piper guineense

Piper guineense is also called Ashanti or West African black pepper. It is a harbeceous

climber, commonly found in the African tropical forest zones. The fruits or berries and leaves are

usually sold in Nigerian markets as condiments and for food flavouring. The fruits are widely

used in Nigerian traditional medicine as a remedy for rheumatism and bronchitis. It belongs to

the group of peppers called the false cubebs. It is of the family Piperaceae.

The proximate composition of three varieties of Piper guineense namely, cultivated and

peppery, wild forest variety, and wild riverine variety, were determined by Isong and Essien

(2005). The cultivated peppery variety has the highest content of crude protein and moisture

(18.9% and 97% respectively), while the wild riverine variety has the highest content of ether

extract, carbohydrate and calories (7.79%, 63.38% and 398cals. respectively). The cultivated

variety has appreciable amounts of phosphorus (1.12mg/100g), potassium (1.2mg/100g), sodium

(0.24mg/100g), zinc (0.18mg/100g), and copper (0.18mg/100g) while the forest variety

contained more calcium (12.38mg/100g), magnesium (1.21mg/100g) and iron (0.85mg/100g).

Piper guineense seeds are dominated by monoterpenoids and moderate sesquiterpenoids.

Like other types of piper, Piper guineense yield an aromatic essential oil on steam distillation.

These organic compounds could be responsible for the repellent and toxic activity of Piper

guineense powder against Sitophilus zea mais (Ukeh et al., 2008).

20

CHAPTER THREE

MATERIALS AND METHODS

3.1 MATERIALS

The materials used for the study were maize (yellow variety), Monodora myristica,

(Ehuru), Piper guineense, (Uziza), Sitophilus zea mais. The maize was purchased from Nsukka

main market. The dried fruits of Monodora myristica and Piper guineense were also purchased

from Nsukka main market. The maize weevil was reared on maize grains.

3.2 PREPARATION OF SAMPLES

The clean undamaged and uninfested maize grains were hand picked, packaged in

moisture proof package and disinfested in the deep freezer for 96hours. The disinfested grains

were allowed to attain room temperature, weighed out in 500g units and treated with the spices at

a dosage level of 2%, 4%, 6%, 8% and 10% of 500g.

3.3 CULTURING OF THE WEEVIL

Sitophilus zeamais was obtained from infested stock of maize from Nsukka main

market. and reared on whole maize at 25+ 20C and 65% relative humidity for two weeks inside a

plastic bucket covered with muslin cloth, in order to allow in air.

3.4 PREPARATION OF THE SPICES

The seed coats of the seeds of Monodora myristica was removed. Both spices were

individually weighed out to obtain 2%, 4%, 6%, 8%, and 10% of 500g that was used for the

study. The spices were reduced to coarse particles using laboratory mortar and pestle to reduce

the extent of volatilization of the active components.

21

3.5 STORAGE OF THE MAIZE

Five hundred grams each of disinfested maize was weighed into plastic containers. The

different concentrations of the spices were added, to the weighed maize samples, except for the

controls which contained no spices. Two hundred maize weevils(Sitophilus zeamais), reared for

two weeks were added to each maize-spice mixture and the content shaken to ensure adequate

contact. Each container was covered with cotton material held in place with rubber band. Each

treatment was replicated three times, and stored for one month. Stored samples were analyzed at

one week interval to determine the protein level as an index of the effect of the infestation on the

quality of the maize.

At the end of the storage period damage assessment and seed viability were determined.

Consumer acceptability was also determined through sensory evaluation of maize products

produced using the stored maize, to evaluate the effect of the spices on the sensory acceptability

of the products.

3.6 PROXIMATE ANALYSIS

Proximate analyses were performed on untreated maize before storage and on the stored

maize samples after the storage period.

3.6.1 DETERMINATION OF MOISTURE CONTENT

The moisture content of the maize samples was determined according to the standard

methods of Association of Official Analytical Chemists (AOAC, 1990). The crucibles were

washed thoroughly and afterwards dried in the oven at 100°C for 1hr. The hot dried crucibles

were cooled in the desiccator and weighed. Two grams of the sample was weighed into the

22

crucible and the total weight taken. The samples were dried at 100°C cooled and weighed.

Drying and cooling continued until a constant weight was obtained.

% moisture content = W2 - W3 X 100

W2 - W1

Where WI = Initial weight of empty crucible.

W2 = Weight of crucible + weight of sample before drying

W3 = Weight of crucible + weight of sample after drying.

3.6.2 DETERMINATION OF ASH CONTENT

The ash content of the maize samples was determined according to the standard methods

of Association of Official Analytical Chemists (AOAC, 1990). Two grams of the sample was

weighed into a preheated, cooled crucible. The sample was charred on a bunsen flame inside a

fume cupboard. The samples were transferred into a preheated muffle furnace at 550°C for 2

hours until a white or light grey ash was obtained. It was cooled in a dessicator, weighed and

the ash content was calculated using the expression:

% ash content = W3 -W1 X 100

W2 - W1

Where W1 = weight of empty crucible

W2 = weight of crucible + weight of sample before ashing

W3 = weight of crucible + weight of sample after ashing

3.6.3 CRUDE PROTEIN DETERMINATION

The protein content of the samples was determined according to the standard methods of

AOAC (1990), using kjeldahl apparatus.

23

(a) Digestion of sample: the sample (2g) was weighed into 30ml kjeldahl flask. and 1 tablet of

kjeldahl catalyst was added. Addition of 25mls of concentrated H2SO4 was done with few

boiling chips. The flask with its content was heated in the fume chamber until the solution

became clear. The solution was cooled to room temperature after which it was transferred

into a 250ml volumetric flask and made up to the level with distilled water.

(b) Distillation: The distillation unit was cleaned and the apparatus set up. A 100ml conical

flask, (receiving flask) containing 5ml of 2% boric acid and two drops of methyl red

indicator was placed under the condenser. Digest (5ml) was pipetted into the distillation unit

through the small funnel, washed down with distilled water, followed by the addition of 5ml

of 40% sodium hydroxide solution. The digestion flask was heated until 100ml of distillate

was collected in the receiving flask. The solution in the receiving flask was titrated with 0.1N

H2SO4 to get pink colour. The same procedure was carried out on the blank.

Calculation

% Nitrogen of sample (% N) = (VS -VB ) x N acid x 0.01401 x 100

W

Where Vs= Volume ( ml) acid required to titrate the sample

VB = Volume (ml) of acid required to titrate the blank.

N acid = Normality of acid (0.1N)

W = Weight of sample in gram

% crude protein = % N x 6.25 (conversion factor).

3.6.4 FAT DETERMINATION

The fat content of the sample was determined using the standard method of AOAC

(1990). A soxhlet extractor with a reflux condenser and a 500ml round bottom flask were fixed.

24

Two grams (2g) of the sample was weighed into a labeled thimble. Petroleum ether (300ml) was

filled into the round bottom flask. The extraction thimble was plugged with cotton wool. The

soxhlet apparatus after assembling was allowed to reflux for about six hours. The thimble was

removed with care, and petroleum ether collected at the top and drained into a container for

reuse. When the flask was free of ether, it was removed and dried at 105°C for 1 hour in an oven.

It was cooled in a dessicator and then weighed.

Calculation

% fat content = weight of fat X 100

weight of sample

3.6.5 CRUDE FIBRE DETERMINATION

The crude fiber content of the sample was determined using the standard method of

AOAC (1990). Petroleum ether was used to defat 2g of sample. This was put in boiled 200ml of

1.25% H2SO4 and boiled for 30 minutes. The solution was filtered through linen or muslin cloth

on a fluted funnel. It was washed with boiling water until it was free of acid. The residue was

returned into 200ml boiling NaOH and allowed to boil for 30 minutes. It was further washed

with 1% HCl, and lastly with boiling water to free it of acid. The final residue was drained and

transferred to silica ash crucible (porcelain crucible), dried in the oven at 100°C for 2 hours and

cooled repeatedly until a constant weight was obtained. The cooled sample was incinerated or

ashed in a muffle furnace at 600°C for 5 hours, cooled in a dessicator and weighed.

Calculation:

% crude fibre = loss in weight after ignition X 100

weight of original sample

25

3.7 DAMAGE ASSESSMENT

To ascertain the efficacy of Piper guineense and Monodora myristica in protecting stored

maize against the maize weevil and extent of damage by Sitophilus zea mais, damage assessment

was calculated at the end of the storage period. One hundred (100) grains were randomly taken

from each container, the numbers of damaged grains (with characteristic holes) and undamaged

grains were counted and weighed. The percent weight loss was calculated following the method

of FAO (1985) using the expression:

% weight loss = UaN- (U+D) 100

UaN

Where U = weight of undamaged fraction in the sample

N = total number of grains in the sample

Ua = average weight of one undamaged grain

D = weight of damaged fraction in the sample

3.8 SEED VIABILITY

At the end of the storage period seed viability was determined using a Petri dish. Ten

seeds with no characteristic holes were selected from each container and placed in a Petri dish

containing water soaked cotton wool. After 4 days the seeds were examined for signs of

germination.

Calculation:

% Seed viability = Number of viable seeds X 100

Total number of seeds

26

3.9 PRODUCTION OF MAIZE PRODUCTS

To evaluate the effect of the spices on the sensory properties of the stored maize, the

stored maize was used to produce two maize products namely fermented maize pap (akamu),

and toasted corn.

3.9.1 PRODUCTION OF FERMENTED MAIZE PRODUCT

Cleaning of maize

Washing

Fermenting / Steeping

Washing

Milling

Sieving

Settling

Draining

Dewatering

Fig. 1 : Flow diagram for pap (Akamu) production

Maize was separated from the spices and the weevils whether dead or alive. The

separated maize was washed using excess water, the washed maize was fermented by soaking in

clean water for 48 hours. The maize was washed and wet milled into a fine slurry. The resultant

slurry was sieved using muslin cloth, allowed to settle, drained to remove excess water, and

dewatered.

27

3.9.2 TOASTED CORN PRODUCTION

Cleaning of maize

Washing

Drying

Toasting

Fig. 2: Flow diagram for toasted corn production

The maize was sorted to remove the spices and the weevils, washed, allowed to dry and

was toasted over fire at about 50˚C for about 30 minutes using a frying pan. These products

were subsequently used for sensory evaluation.

3.10 SENSORY EVALUATION

The fermented maize product was produced as shown in Fig.1. Twenty grams of the

product was rehydrated with water (30ml) at room temperature and subsequently boiling water

was added to form a gruel. Nothing else was added to the gruel before serving to the panelists to

avoid any alteration in taste. The toasted maize was produced as shown in Fig .2. The toasted

maize was served with toasted groundnuts. Prepared maize gruels were also administered

separately.

Products were subjected to sensory evaluation using a twenty member untrained panel.

Quality attributes such as colour, flavour, taste and general acceptability were evaluated.

Panelists scored the two food products on a 5 point hedonic scale where 5 represents the most

28

desirable attribute (very desirable) and I represents the least desirable attribute (very

undesirable).

3.11 STATISTICAL ANALYSIS

Data generated from the storage study was analysed using one way ANOVA. The means

were separated using new Duncan’s multiple range test at (P<0.05).

29

CHAPTER FOUR

RESULTS AND DISCUSSION

4.1 PROXIMATE COMPOSITION OF UNTREATED MAIZE SAMPLE (BEFORE

STORAGE)

Table 2: Proximate composition of untreated maize sample before storage

CONSTITUENT PERCENT COMPOSITION (%)

Moisture 14.01±0.01

Fibre 2.11±0.01

Ash 3.01±0.01

Fat 3.11±0.01

Protein 9.29±0.02

Carbohydrate 68.48±0.04

Values are means of triplicate determination ±SD

According to Cortez and Wild-Altamirano (1972), maize grains contain 11.2% moisture,

2.9% ash, 9.1% protein, 1.8% fibre, 72.8% carbohydrate, and 2.2% fat. Ihekoronye and Ngoddy

(1985), reported the following as ranges for proximate composition of maize grains, moisture

12%-15%, fibre 2% to 3%, ash 3%, fat 3%-5%, protein 9%-10% and carbohydrate 65%-84%. It

is evident that the proximate composition of untreated maize sample in this study (Table 1)

compares with values reported by these authors.

30

Table 3: Proximate composition of maize samples treated with different concentrations

of Monodora myristica and Piper guineense at the end of storage period of one month (%)

SAMPLE Carbohydrate

(%)

Protein (%) Fat (%) Fibre (%) Moisture (%) Ash (%)

MC 76.87a+ 0.01 5.43

bc + 0.02 1.72

bc + 0.01 2.38

a + 0.01 12.00

bc + 0.03 1.60

bc + 0.03

M2 76.77a+ 0.01 5.48

bc + 0.01 1.77

bc + 0.01 2.35

a + 0.01 12.01

bc + 0.02 1.62

bc + 0.03

M4 76.10a + 0.01 5.86

bc + 0.01 1.81

bc + 0.01 2.32

a + 0.01 12.23

bc + 0.01 1.68

bc + 0.01

M6 75.75a + 0.01 6.00

bc + 0.01 1.86

ab + 0.01 2.31

ab + 0.01 12.38

bc + 0.01 1.70

bc + 0.03

M8 74.55ab

+ 0.01 6.79ab

+ 0.02 1.92ab

+ 0.03 2.32 a + 0.01 12.52

ab + 0.01 1.90

ab + 0.01

M10 74.08ab

+ 0.01 6.86ab

+ 0.01 1.98ab

+ 0.01 2.31ab

+ 0.02 12.67ab

+ 0.02 2.10 a + 0.01

PC

P2

76.87a + 0.01

75.07ab

+ 0.01

5.43bc

+ 0.02

6.77ab

+ 0.02

1.72bc

+ 0.01

1.96ab

+ 0.03

2.38a + 0.01

2.28ab

+ 0.03

12.00bc

+ 0.03

12.16bc

+ 0.01

1.60bc

+ 0.03

1.76ab

+ 0.01

P4 73.23ab

+ 0.01 7.00ab

+ 0.03 2.12ab

+ 0.01 2.28ab

+ 0.03 13.50ab

+ 0.01 1.87ab

+ 0.01

P6 71.78ab

+ 0.01 7.62ab

+ 0.01 2.79 a + 0.01 2.26

bc + 0.01 13.55

a + 0.02 2.00

ab + 0.03

P8 69.60bc

+ 0.28 8.91 a + 0.03 2.80

a + 0.04 2.20

bc + 0.01 13.70

a + 0.03 2.79

a + 0.03

P10 69.07bc

+ 0.02 9.00 a + 0.03 2.86

a + 0.01 2.20

bc + 0.03 13.86

a + 0.01 3.01

a + 0.01

Values are means of triplicate determinations + SD

Values on the same column bearing different superscripts are significantly different (P<0.05).

KEY

MC = Control (does not contain any spice) PC = Control (does not contain any spice)

M2= Treated with 2% Monodora myristica P2 = Treated with 2% Piper guineense

M4 = Treated with 4% Monodora myristica P4 = Treated with 4% Piper guineense

M6 = Treated with 6% Monodora myristica P6 = Treated with 6% Piper guineense

M8 = Treated with 8% Monodora myristica P8 = Treated with 8% Piper guineense

31

M10 = Treated with 10% Monodora myristica P10 = Treated with 10% Piper guineense

Table 3 shows the proximate composition of maize samples treated with different

concentration of Monodora myristica and Piper guineense at the end of storage period of one

month.

The result shows that there were significant (P< 0.05) differences in the proximate

composition of the samples after a storage period of one month. There were decreases in protein,

fat, ash, and moisture content of the samples after a storage period of one month with different

concentrations of Monodora myristica and Piper guineense. The protein content of the control

sample decreased from the initial value of 9.29% to 5.43% after storage. In samples treated with

Monodora myristica the values of protein content ranged from 5.48% to 6.86%, while in samples

treated with Piper guineense the values ranged from 6.77% to 9.00%, indicating that the control

was the most affected, followed by the samples treated with Monodora myristica, while the

samples treated with Piper guineense was the least affected. The same trend was observed in fat,

moisture and ash contents.

This decrease observed in protein, fat, moisture and ash content is due probably to the

infestation by Sitophilus zeamais which fed on the maize grains. This explains why the sample

(MC), which is the control, containing no spice was the most affected.

An increase was observed in the fibre content at the end of the storage period. This

increase was at the highest level in the control from 2.12% to 2.38%. This is believed to be as a

result of the mode of feeding of the weevils. They gain entrance into the interior of the grains

and feed on the germ leaving behind the fibrous part of the grains. The higher fibre content of the

control and the samples treated with Monodora myristica is believed to be as a result of the

weevils feeding more on them than in the samples treated with Piper guineense, due probably to

the non pungent nature of Monodora myristica. In the samples treated with Piper guineense high

32

rate of mortality was observed by the end of the storage. This may be attributed to the presence

of strong pungent odour from Piper guineense thus making it impossible for the weevils to feed

on the maize samples. Also the pungent nature may have exerted a toxic effect by disrupting

normal respiratory activity of the weevils thereby resulting in asphyxiation and subsequent death.

(Adedire and Ajayi, 1996).

33

4.2: Effect of spice treatment and storage time on protein content of maize.

key

MC-0% concentration

M2-2% concentration

M4-4% concentration

M6-6% concentration

M8-8% concentration

M10-10% concentration

Figure 1 : Effects of concentration of Monodora myristica and storage

time on protein content of maize

5

5.5

6

6.5

7

7.5

8

8.5

9

9.5

10

1 2 3 4

Time (weeks)

Prot

ein

cont

ent (

%)

MC

M2

M4

M6

M8

M10

Figure 3:

34

4.2.1 Effect of concentration of Monodora myristica and storage time on protein

content of maize

Figure 3 shows the effect of concentration of Monodora myristica and storage time on

protein content of maize. There were significant differences (P<0.05) in protein content amongst

samples at the end of the storage period of one month.

The protein content of maize grains was not affected in the first week. As storage entered

the second week the decrease became noticeable. The protein content of the control sample (MC)

decreased from 9.29% to 7.91%. M2 decreased from 9.29% to 8.02%. M4 decreased from 9.25%

to 8.02%. M6 decreased from 9.29% to 8.98%. M8 decreased from 9.255 to 8.98% and M10

decreased from 9.26% to 9.02. Further decrease was recorded in the third week and by the end of

the fourth week the control has decreased from the initial value of 9.28% recorded in the first

week to 5.44%.This shows that the weevils attacked the maize grains to a large extent.

Monodora myristica was not found effective in preventing the attack by the weevils it was not

repulsive to the weevils this is probably because the spice has been reported to be aromatic and

mild (http://www.celnet.org.uk/recipes/spice) and thus could not deter the weevils from feeding

on the maize grains. Although at higher concentrations of 6%, 8% and 10% the spice exhibited a

mild protective effect relative to the control. However the 2% and 4% concentrations, were not

very effective in providing total protection for the maize grains.

35

36

4.2.2 Effect of concentration of Piper guineense and storage time on protein content of

maize

Figure 4 shows the effect of concentration of Piper guineense and storage time on

protein content of maize. There were significant differences (P<0.05) in protein content

amongst samples at the end of one month storage period.

There was a slight reduction in protein content as storage progressed. The reduction was

dose dependent with samples treated with 6%, 8% and 10% concentrations of Piper guineense

offering greater protection and hence little decrease in protein content. In the first week there

were no changes observed, as storage entered the second week the reduction in protein content

became more noticeable as sample P2 treated with 2% concentration of Piper guineense

decreased from the initial 9.27% recorded in the first week to 6.77% by the end of the fourth

week. P4 decreased from 9.30% to 7.02%, sample P6 decreased from 9.31% to 7.64%, sample

P8 decreased from 9.27% to 8.91% and sample P10 decreased from 9.25% to 9.02 %.

The trend shows that the weevils could not feed effectively on the maize grains. This is

believed to be due to the ability of the Piper guineense to deter weevils from feeding on the

maize grains. The extreme pungent odour of Piper guineense was evidently repulsive and

perhaps toxic to the weevils as a greater percentage of the weevils were observed to be dead

before the end of the storage. Thus Piper guineense offered more protection than Monodora

myristica.

37

4.3 Effect of spice treatment on seed viability after storage

Table 4: Effect of spice treatment on percent seed viability after storage

SAMPLE VIABILITY (%)

MC Control (does not contain any spice) 6.67e + 5.77

M2 Treated with 2% Monodora myristica 13.33d

+5.77

M4 Treated with 4% Monodora myristica 13.33d +5.77

M6 Treated with 6% Monodora myristica 16.67c +5.77

M8 Treated with 8% Monodora myristica 20.00c +10.00

M10 Treated with 10% Monodora myristica 20.00c +10.00

PC Control (does not contain any spice ) 6.67e +5.77

P2 Treated with 2% Piper guineense 50.00b +17.32

P4 Treated with 4% Piper guineense 50.00b

+0.00

P6 Treated with 6% Piper guineense 50.00b +0.00

P8 Treated with 8% Piper guineense 50.00b +0.00

P10 Treated with 10% Piper guineense 76.67a +5.77

Values are means of triplicate determinations + SD

Mean values on the same column bearing different superscripts are significantly different

KEY

PC = Control (does not contain any spice) MC = Control (does not contain any spice)

P2 = Treated with 2% Piper guineense M2= Treated with 2% Monodora myristica

P4 = Treated with 4% Piper guineense M4= Treated with 4% Monodora myristica

P6 = Treated with 6% Piper guineense M6 = Treated with 6% Monodora myristica

P8 = Treated with 8% Piper guineense M8 = Treated with 8% Monodora myristica

P10 = Treated with 10% Piper guineense M10 = Treated with 10% Monodora myristica

Table 4, shows the effect of spice treatment on percent seed viability after storage.The

result shows that there were significant (P<0.05) differences in seed viability, the samples treated

with Piper guineense were more viable than samples treated with Monodora myristica and the

38

control was the least viable. This result is in line with earlier observations of Piper guineense

offering more protection to grains by deterring the attack by the weevils, which led to a greater

protection and also to more viable grains.

4.4 Effect of spice treatment on damage of maize samples after storage

Table 5: Effect of spice treatment on percent damage of maize after storage

SAMPLE DAMAGE ASSESSMENT (%)

MC Control (does not any spice) 44.73a +6.39

M2 Treated with 2% Monodora myristica 36.10b +3.18

M4 Treated with 4% Monodora myristica 38.10b +2.25

M6 Treated with 6% Monodora myristica 22.20c +3.81

M8 Treated with 8% Monodora myristica 18.83c +1.04

M10 Treated with 10% Monodora myristica 16.50c +0.50

PC Control (does not contain any spice) 44.73a

+ 6.39

P2 Treated with 2% Piper guineense 11.67d

+ 1.53

P4 Treated with 4% Piper guineense 12.67d

+ 0.58

P6 Treated with 6% Piper guineense 8.60de

+ 0.36

P8 Treated with 8% Piper guineense 5.27e + 0.15

P10 Treated with 10% Piper guineense 4.23e

+ 0.25

Values are means of triplicate determinations + SD.

Mean values on the same column bearing different superscripts are significantly different (P<0.05).

KEY

MC = Control (does not contain any spice) PC = Control (does not contain any spice)

M2= Treated with 2% Monodora myristica P2 = Treated with 2% Piper guineense

M4 = Treated with 4% Monodora myristica P4 = Treated with 4% Piper guineense

M6 = Treated with 6% Monodora myristica P6 = Treated with 6% Piper guineense

M8 = Treated with 8% Monodora myristica P8 = Treated with 8% Piper guineense

M10 = Treated with 10% Monodora myristica P10 = Treated with 10% Piper guineense

39

Table 5, shows the extent of damage done to treated and untreated maize samples by the

weevil. The results compared well with those reported by Udo (2005) and Arannilewa and

Odeyemi (2007). There were significant differences (P<0.05) in the extent of damage amongst

the spice treated samples relative to the control in reducing damage caused by Sitophilus

zeamais. The result therefore suggest that the two spices displayed some degree of potency as

control agents. Although none of the spices offered complete protection Piper guineense was

more effective in protecting the maize than Monodora myristica. The potency was dose

dependent with higher doses offering more protection. This trend could also be attributed to the

toxic effect of Piper guineense on the weevils, which Monodora myristica lacks. The high

pungent effect of Piper guineense did not encourage weevil infestation and therefore offered

greater protection.

40

4.5: Sensory quality of products from treated, stored maize samples

(Pap and toasted corn)

4.5.1: Table 6: Sensory scores of pap produced from treated, stored maize samples

SAMPLE

COLOUR

FLAVOUR

TASTE

GENERAL

ACCEPTABILITY

MC 4.20a±0.62 4.60

a±0.50 4.75

a±0.44 4.55

a±0.51

M2 4.25a±o.55 4.30

a±0.47 4.55

ab±0.51 4.55

a±0.51

M4 4.25a±0.55 4.30

a±0.47 4.35

ab±0.59 4.40

a±0.50

M6 4.20a±0.62 4.25

a±0.55 4.10

bc±0.97 4.40

a±0.50

M8 4.15a±0.49 3.80

b±0.89 4.00

bc±1.08 4.30

a±0.57

M10

PC

4.25a±0.64

4.20a+ 0.62

3.55b±1.09

4.60a+ 0.50

3.60c±1.09

4.75a+0.44

3.70b±0.86

4.55a+0.51

P2 4.30a±0.66 4.20

ab±0.62 4.55

a±0.51 4.45

a±0.60

P4 4.45a±0.51 4.30

ab±0.47 4.50

a±0.51 4.35

ab±0.59

P6 4.25a±0.55 4.25

ab±0.55 4.40

a±0.58 4.30

ab±0.47

P8 4.20a±0.52 4.05

b±0.89 3.95

bc±1.05 3.90

b±0.91

P10 4.15a±0.49 3.50

c±0.89 3.70

c±0.92 3.95

b±0.99

Values are means of triplicate determinations ±SD

Values on the same column bearing the same superscripts are not significantly different

(P>0.05).

KEY

MC = Control (does not contain any spice) PC = Control (does not contain any spice)

M2= Treated with 2% Monodora myristica P2 = Treated with 2% Piper guineense

M4 = Treated with 4% Monodora myristica P4 = Treated with 4% Piper guineense

M6 = Treated with 6% Monodora myristica P6 = Treated with 6% Piper guineense

M8 = Treated with 8% Monodora myristica P8 =Treated with 8% Piper guineense

M10 = Treated with 10% Monodora myristica P10 = Treated with 10% Piper guineense

41

Table 6, shows the sensory scores of pap produced from treated, stored maize samples.

Treatment affected flavour, taste, and general acceptability. The control which contained no

spice was the most acceptable. There were no significant differences in samples treated with 2%,

4%, and 6% concentrations of spice thus they were more acceptable than samples treated with

8% and 10% concentrations.

Since the control which contained no spice was the most acceptable, it shows that weevil

infestation has no adverse effect on acceptability of the product by the panelists.

In the production of pap, the maize grains were thoroughly washed using excess water.

During this period of washing and soaking in water the deposits of the spices on the maize grains

were washed off, in those samples that contained less concentrations of spice it is believed that

they were washed off entirely thus they were more acceptable just like the control which stands

as a standard, but in those samples that contained higher concentrations of the spice (samples

treated with 8% and 10% concentrations) they still retained some measure of the spice after

soaking and subsequent washing, and this affected the acceptability of the product by panelists.

42

4.5.2 Table 7: Sensory scores of toasted corn produced from treated, stored maize

samples

SAMPLE COLOUR FLAVOUR TASTE GENERAL

ACCEPTABILITY

MC 4.25a±0.44 4.75

a±0.44 4.35

a±0.59 4.30

a±0.80

M2 4.15a±0.37 4.40

a±0.68 4.05

a±0.60 4.00

a±0.73

M4 4.20a±0.41 3.65

b±0.81 3.30

b±0.92 3.25

b±0.85

M6 4.40a±0.50 3.20

bc±0.69 3.10

b±0.79 2.90

b±0.64

M8 4.10a±0.44 2.85

c±0.88 2.85

b±1.14 2.35

c±0.81

M10 4.40a±0.50 2.35

d±0.93 1.85

c±0.75 1.95

c±0.89

PC 4.25a±0.44 4.75

a±0.44 4.35

a±0.59 4.30

a±0.80

P2 4.30a±0.47 4.15

b±0.81 3.65

b±0.59 3.50

b±0.69

P4 4.30a±0.57 3.45

c±0.76 2.85

c±0.93 2.90

c±0.64

P6 4.55a±0.51 2.75

d±0.97 2.25

d±0.59 2.25

d±0.63

P8 4.25a±0.44 2.45

d±0.89 1.75

e±0.64 1.65

e±0.59

P10 4.45a±0.51 2.30

d±0.92 1.60

e±0.59 1.55

e±0.51

Values are means of triplicate determinations ±SD

Values on the same column bearing the same superscripts are not significantly different (P>0.05)

KEY

MC = Control (does not contain any spice) PC = Control (does not contain any spice)

M2= Treated with 2% Monodora myristica P2 = Treated with 2% Piper guineense

M4 = Treated with 4% Monodora myristica P4 = Treated with 4% Piper guineense

M6 = Treated with 6% Monodora myristica P6 = Treated with 6% Piper guineense

M8 = Treated with 8% Monodora myristica P8 =Treated with 8% Piper guineense

M10 = Treated with 10% Monodora myristica P10 = Treated with 10% Piper guineense

43

Table 7, shows sensory scores of toasted corn produced from treated, stored maize

samples.Treatment did not affect the colour of the products since there were no significant

differences between samples.

There were significant differences in flavour, taste and general acceptability. The control

and the sample treated with 2% concentration of Monodora myristica received the highest panel

scores. This is believed to be due to the fact that the panelists were used to the control that had

no spice treatment. This shows that the infestation of the product by the weevils did not affect the

acceptability of the product, rather the spice treatment did. The sample treated with 2%

Monodora myristica was rated higher than others probably due to the aromatic nature of the

spice. Since the 2% concentration was low the product had a mild acceptable flavour and taste

this is believed to have made it more acceptable to the panelists.

In toasting corn the samples were washed and toasted without soaking, because of this

the spice were retained more in the products and this affected flavour, taste and general

acceptability. The panelists complained that the samples treated with Piper guineense were

pepperish and thus highly unacceptable.

44

CHAPTER FIVE

CONCLUSION AND RECOMMENDATIONS

5.1 CONCLUSION

This research work shows that the fruits of Monodora myristica and Piper guineense

have anti weevil infestation potentials when used in storing maize. Piper guineense proved to

have offered more protection than Monodora myristica. The protection was dose dependent,

with higher doses offering better protection. Both spices are readily available to farmers in the

rural areas and can be used for short term storage of maize grains.

From the study it was established that:

1. The high pungent effect of Piper guinense deterred attack of the grains by the weevils. The

protein of samples treated with Piper guineense was conserved better than the protein of

samples treated with Monodora myristica.

2. There were significant differences (P<0.05) in viability of seeds stored with the spices. The

samples treated with Piper guineense were more viable than samples treated with

Monodora myristica and the control was the least viable.

3. There were significant differences (P<0.05) in the extent of damage amongst the spice

treated samples over the control in reducing damage caused by Sitophilus zeamais. The

higher doses (8% and 10%) of Piper guineense caused the lowest damage, thus offered

better protection than Monodroa myristica.

4. The treatment did not affect the colour of the fermented maize pap (akamu) and toasted

corn products. The treatment rather affected flavour, taste and general acceptability. The

control and the sample treated with 2% concentration of Monodora myristica were the most

acceptable.

45

5.2 RECOMMENDATION

Air tight containers should be used for storage, this is believed to offer more protection as

weevil infestation would be prevented by the pungent nature of the spice and also by

asphyxiation.

46

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http://www.grainscanada.gc.ca/storage

http://www.en.wikipedia.org/wiki/maize

http://www.en.wikipedia.org/wiki/monodora myristica

50

APPENDIX 1

SENSORY EVALUATION SCORE SHEET

Appendix 1a PRODUCT- PAP

PLEASE ACCESS THE PRODUCTS AND INDICATE YOUR REACTION

COLOUR PCa P2a P4a P6a P8a P10a MCa M2a M4a M6a M8a M10a

Very desirable

Moderately

desirable

Neither desirable nor

undesirable

undesirable

Very undesirable

FLAVOUR

Very good

Good

Neither good nor

bad

Bad

Very bad

TASTE

Very good

Good

Neither good nor

bad

Bad

Very bad

GENERAL

ACCEPTABILITY

Completely

acceptable

Acceptable

Indifferent

Unacceptable

Completely

unacceptable

51

Appendix 1b PRODUCT-TOASTED CORN

PLEASE ACCESS THE PRODUCTS AND INDICATE YOUR

REACTION

COLOUR PCa P2a P4a P6a P8a P10a MCa M2a M4a M6a M8a M10a

Very desirable

Moderately

desirable

Neither desirable nor

undesirable

undesirable

Very undesirable

FLAVOUR

Very good

Good

Neither good nor

bad

Bad

Very bad

TASTE

Very good

Good

Neither good nor

bad

Bad

Very bad

GENERAL

ACCEPTABILITY

Completely

acceptable

Acceptable

Indifferent

Unacceptable

Completely

unacceptable

52

APPENDIX 2

EFFECT OF SPICE TREATMENT AND STORAGE TIME ON PROTEIN

CONTENT OF MAIZE

Appendix 2a: Effect of concentration of Monodora myristica and storage time on

Protein content of maize

WEEKS

SAMPLE 1 2 3 4 Treatment

mean

MC 9.28

±0.015

7.91

±0.099

6.59

± 0.015

5.44

± 0.015

7.31e

M2 9.26

± 0.015

8.02

±0.020

6.57

±0.012

5.46

± 0.020

7.33e

M4 9.25

± 0.010

8.02

± 0.010

6.67

± 0.072

5.86

±0.015

7.45d

M6 9.29

± 0.015

8.98

±0.012

6.82

± 0.020

6.02

±0.025

7.78c

M8 9.25

±0.020

8.98

± 0.017

7.01

±0.015

6.79

±0.015

7.97b

M10 9.26

±0.010

9.02

±0.021

8.67

±0.015

6.86

±0.006

8.04a

Weeks

mean

9.26a 8.49

b 6.76

c 6.07

d

53

Appendix 2b: Effect of concentration of Piper guineense and storage time on

Protein content of maize

WEEKS

SAMPLE 1 2 3 4 Treatment

mean

MC 9.28

±0.015

7.91

±0.099

6.59

±0.015

5.44

± 0.015

7.31e

P2 9.27

± 0.011

8.29

±0.015

7.58

±0.015

6.77

± 0.015

7.98d

P4 9.30

± 0.020

8.58

±0.020

7.69

± 0.011

7.02

±0.025

8.15c

P6 9.31

± 0.021

8.98

±0.010

8.82

±0.020

7.64

±0.020

8.69b

P8 9.27

±0.015

9.,20

±0.015

8.98

±0.020

8.91

±0.015

9.09a

P10 9.25

±0.015

9.25

±0.015

9.12

±0.021

9.02

±0.021

9.16a

Weeks

mean

9.28a 8.70

b 8.13

c 7.47

d

54

APPENDIX 3

ANOVA for percent seed viability after storage

Sum of

squares

Df Mean

square

F Sig.

Viability (M)

Between

groups

383.333

5 76.667 1.971 0.150

Within

groups

466.667 12 38.889

Total 850.000 17

Viability (P)

Between

groups

5044.444 5 1008.889 16.509 0.000

Within

groups

733.333 12 61.111

Total 5777.778 17

(M)-Monodora myristica (P) – Piper guineense

55

APPENDIX 4:

ANOVA for percent damage assessment after storage

Sum of

squares

Df Mean

square

F Sig.

Damage

assessment

(M) Between

groups

2056.784 5 411.357 33.409 0.000

Within

groups

147.753 12 12.313

Total 2204.538 17

Damage

assessment

(P) Between

groups

3452.723 5 690.545 98.819 0.000

Within

groups

87.393 12 7.283

Total 3540.116 17

(M)- Monodora myristica (P)- Piper guineense

56

APPENDIX 5:

Appendix 5a: Sensory evaluation ANOVA for pap produced from treated, stored

Maize samples

Sum of

squares

Df Mean

square

F Sig.

Colour (M)

between

groups

0.167 5 0.033

0.099 0.992

Within groups 38.200 114 0.335

Total 38.367 119

Flavour (M)

between

groups

14.767 5 2.953 5.896 0.000

Within groups 57.100 114 0.501

Total 71.867 119 3.415

Taste (M)

between

groups

17.075 5 0.683 5.001 0.000

Within groups 77.850 114

Total 94.925 119

General

acceptability

(M) between

groups

10.067 114 2.013 5.752 0.000

Within groups 39.900 119 0.350

Total 49.967 5

Colour (P)

between

groups

1.142 114 0.228 0.726 0.605

Within groups 35.850 119 0.314

57

Total 36.992 5

Flavour (P)

between

groups

13.400 114 2.680 5.887 0.000

Within

groups

51.900 119 0.455

Total 65.300 5

Taste (P)

between

groups

15.942

114 3.188 6.093 0.000

Within groups 59.650 119 0.523

Total 75.592 5

General

acceptability

(P) between

groups

7.100 114 1.420 2.820 0.019

Within

groups

57.400 119 0.504

Total 64.500

(M)- Monodora myristica (P)- Piper guineense

58

Appendix 5b: Sensory evaluation ANOVA for toasted corn produced from treated,

Stored maize samples

Sum of

squares

df Mean

square

F Sig.

Colour (M) between

groups

1.600 5 0.320 1.593 0.168

Within groups 22.900 114 0.201

Total 24.500 119

Flavour (M) between

groups

84.467 5 16.893 29.447 0.000

Within groups 65.400 114 0.574

Total 140.867 119

Taste (M) between

groups

79.900 5 15.980 23.782 0.000

Within groups 76.600 114 0.672

Total 156.500 119

General acceptability

(M) between groups

83.875 5 16.775 26.840 0.000

Within groups 71.250 114 0.625

Total 155.125 119

Colour (P) between

groups

1.500 5 0.300 1.230 0.300

Within groups

27.800

114

0.244

Total 29.300 119

Flavour (P) between

groups

97.442 5 19.488 29.175 0.000

Within groups 76.150 114 0.668

Total 173.592 119

Taste (P) between

groups

119.042 5 23.808 46.836 0.000

Within groups 57.950 114 0.508

Total 176.992 119

General acceptability

(P) between groups

117.342 5 23.468 55.448 0.000

Within groups 48.250 114 0.423

Total 165. 592 119

59