ABSTRACT
Fungi are major spoilage agents of cereals and other foodstuffs before and during storage. Studies were conducted to determine the fungal pathogens of stored rice (Oryza sativa), maize (Zea mays), and millet (Pennisetum thyphodes) and the effect of fungal spoilage on the proximate and vitamin composition. Samples of deteriorated rice, maize and millet grains were sourced from Ubani market and investigated for fungal growth at plant pathology laboratory in the department of Plant Science and Biotechnology. Isolation of fungi from the grains was carried out on potato dextrose agar (PDA) and water agar (WA). The grains were surface sterilized onto WA and incubated for 3 days at room temperature (25 ± 20c) on the laboratory bench. Emerging fungal growth were transferred to PDA and subsequently sub cultured to obtain pure cultures. The pure cultures were identified and subjected to pathogenicity test. The results showed that Aspergilus, rhizopus, Penicillium, Mucor and Fusarium were spoilage pathogens of the grains. Proximate and vitamin analyses were carried out on the infected and healthy grains. Results of the proximate analysis showed that carbohydrate, fibre, ash and moisture content are significantly higher (LSD: 0.05) in the healthy samples than the infected samples. The carbohydrate and fibre content of the healthy samples ranged from 80.39 ± 39 to 69.80± 0.08 and 0.97 ± 0.14 to 2.41 ± 0.03 respectively. While that of the infected samples ranged from 79.63 ± 0.09 to 69.55 ± 0.09 and 0.46 ± 0.02 to 1.99 ± 0.14. The infected samples had higher protein values which ranged from 11.79 ± 0.09 to 15.52 ± 0.10. While the healthy samples ranged from 10.82 ± 0.05 to 15.29 ± 0.09. The infected samples had higher protein content because advanced fungal deterioration increases protein content mathematically. Results of the vitamin analysis showed that the healthy samples had very high vitamin C than any other vitamin. The value of vitamin C of the healthy samples ranged from 28.15 ± 0.05 to 0.29 ± 0.01 while that of the infected samples ranged from 3.28 ± 0.10 to 5.16 ± 0.20.
TABLE OF CONTENTS
Title page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of contents vi
List of table’s ix
List of plates x
Abstract xi
CHAPTER ONE
1.0 INTRODUCTION 1
1.1 JUSTIFICATION 3
1.2 AIMS AND OBJECTIVES OF THE STUDY 3
CHAPTER
TWO
LITERATURE REVIEW 4
2.0 GENERAL DESCRIPTION OF RICE, MAIZE AND
MILLET 4
2.1 RICE (Oryza
sativa Linn) 4
2.2 MAIZE (Zea
mays Linn) 6
2.3 MILLET (Pennisetum
typhoides Stapf. &Hubbard) 8
2.4 COMPOSITION OF RICE, MAIZE AND MILLET 10
2.5 HEALTH BENEFITS OF CEREALS 11
2.6 FUNGI AS A PATHOGEN TO RICE, MAIZE AND
MILLET 12
2.6.1 FACTORS INFLUENCING FUNGAL GROWTH AND
DETERIORATION OF RICE, MAIZE AND MILLET 13
2.7 NUTRITIONAL CHANGES IN DETERIORATED GRAINS
14
2.7.1 CARBOHYDRATES 15
2.7.2 PROTEIN 15
2.7.3 VITAMINS 15
2.8 AESTHETIC CHANGES IN THE GRAINS 15
2.9 CONTROL OF FUNGAL DETERIORATION IN RICE,
MAIZE 16
AND
MILLET
CHAPTER THREE
3.0 MATERIALS AND METHOD 17
3.1 COLLECTION
OF FOOD SAMPLES 17
3.2 PREPARATION
OF MEDIUM 17
3.3 ISOLATION AND IDENTIFICATION OF FUNGI 17
3.4 SUBCULTURING
AND PURIFICATION 18
3.5 PATHOGENICITY
TEST 18
3.6 CONFIRMATION OF ISOLATES USED FOR 19
PATHOGENICITY TEST
3.7 CHARACTERIZATION
OF PURIFIED MICRO ORGANISM 19
3.8 PROXIMATE AND VITAMIN COMPOSITION OF RICE, 19
MAIZE AND MILLET
3.9 STATISTICAL
ANALYSIS 19
CHAPTER
FOUR
4.1 RESULTS 20
CHAPTER
FIVE
5.1 DISCUSSION 25
5.2 CONCLUSION 27
5.3 RECOMMENDATION 27
REFERENCES 28
APPENDIX 34
LIST OF TABLES
Table
2.1 Nutrional Information on Rice 5
Table
2.2 Vitamin Composition of Rice 6
Table
2.3 Nutritional Value of Maize 7
Table
2.4 Vitamin Composition of Maize 8
Table 2.5 Nutritional Value for Millet Per 100g
(3.5 oz) 9
Table 2.6 Vitamin Composition of Millet 9
Table 4.1 Frequency of occurrence of isolated
pathogen 20
Table 4.2 Proximate Compositions of Healthy and Infected
Rice, Maize and Millet 21
Grains
Table
4.3 Vitamin Compositions of Healthy
and Infected Rice, 23
Maize and Millet Grains
LIST OF PLATES
Plate 1 Mucor spp
34
Plate 2 Aspegillus spp 34
Plate 3 Rhizopus spp 35
Plate 4 Fusarium spp 35
Plate 5 Penicillium spp 36
Plate 6 Aspergillus spp 36
CHAPTER ONE
1.0 INTRODUCTION
Cereals
or grains belong to the monocot family Poaceae and are cultivated widely to
obtain the edible components of their fruit seeds (Masih et al., 2014). Botanically, these are called caryopsis and are
structurally divided into endosperm, germ and bran. Cereals are good sources of
carbohydrates and are consumed in huge quantities than any other type of crop (Mbithi
et al., 2002). They are rich in
complex carbohydrates which provide energy and also contain fibre, proteins,
fats, lipids, minerals, vitamins and enzymes that enrich the overall health and
help prevent cancer, constipation, colon disorders and high blood sugar levels (Penagini
et al., 2013). Africa is a major
producer of several cereals including sorghum (sorghum bicolor), millet (Pennisetum
typhoides), maize (Zea mays) and
African rice (Oryza glabberima) which
are widely consumed by people with varying food preferences and socio-economic
background. More than 300 million people in the sub-Saharan Africa depend on
these cereals as a source of food and livelihood (Baudron et al., 2015). In Nigeria in particular, rice, maize and millet are of unique
importance because they can be grown across the ecological zones making them
readily available.
However,
cereals are susceptible to several diseases both in the field and during
storage. The invasion of microbial pathogens especially fungi is considered the
most critical facts in deterioration of cereals (Amadi et al., 2009).
Fungi
are ubiquitous plant pathogens that are major spoilage agents of food and
feedstuffs. The infection of plants by various fungi not only results in
reduction in crop yield and quality with significant economic losses but also
contamination of grains with poisonous fungal secondary metabolites called
mycotoxins. The ingestion of such mycotoxin contaminated cereals by human
beings and animals has enormous public health significance, because these
toxins are capable of causing diseases in man and animals (Bhat and Vasanthi,
2003).
Mycotoxins
are secondary metabolites of fungi which are formed during enzymatic reactions.
The Chemical characteristics and biological activities of mycotoxins are very
wide and able to cause different pathological and pathohistological changes
which cause serious effects in humans, the final consumers at certain dosages
(Amadi and Adeniyi, 2009).
Recently,
some chemical compounds like mycotoxin binders (Hydrated Sodium Calcium
Aluminosilcates) and mould inhibitors (Calcium propionate) have been used to
eliminate the presence of storage fungi.
Fungi
growing in cereals could be divided in general into two groups, field and
storage fungi. Genera Aspergillusare typical storage fungi and their higher amount in cereals
are connected with a higher humidity and colder region (Agboola, 1992). There
are more than 100,000 species of mould producing more than 300 metabolites
which have a toxic potential for humans and animals (Hintz, 1990).
It
is known that fungi of the genera Aspergillus
and Penicillium produce carcinogenic
mycotoxins, aflatoxins and ochratoxins. While Fusarium species produce the oestrogenic toxin Zearalenone. Cereals
as energy source are the main ingredients in the making of feed (up to 90%) for
all kinds and categories of fish andereal feedstuffs are vulnerable to fungal
contamination either prior to harvesting of the cereal or due to poor storage
conditions. In such condition the storage fungi multiply and their metabolite
cause changes in the feed quality.
1.1 JUSTISFICATION OF THE STUDY
Since
rice, maize and millet are highly consumed in Nigeria and are used in the
production of animal feed, a knowledge of the fungal contaminants of these
grains in a major cereal producing country like Nigeria would be a rational
basis for their elimination in the grains through careful selection, proper storage
and treatment with mycotoxin binders before use. Secondly proper and rationale
speculation as to the type of animal and human diseases expected from fungal
contaminated food/feed and pragmatic strategies to averting the hazards would
be put in place. In addition, the knowledge of the nutrient depleting effect of
the contaminants on such cereals would make consumers and traders to settle for
the best quality when choosing grains for food and feed.
Based
on these premises, this study was conducted to determine the kinds of fungi
responsible for deterioration of rice,
maize and millet under natural conditions in Abia state.
1.2 AIMS AND OBJECTIVES OF THE STUDY
1.
To isolate and identify the fungi that is responsible for the deterioration of
rice, maize and millet grains.
2. To determine the frequency of occurrence of
the isolated fungi.
3. To
compare the nutritional value of the healthy samples with that of the
deteriorated samples.
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