ABSTRACT
The microbial load and quality of yam flour purchased from three markets in Aba was examined using standard microbiological method. The total viable count of market A ranges from 1.2x104cfulml to 6.85x105cfu/ml, market B ranges also from 3.96x104cfu/ml to 4.45x105cfu/ml while market C had a viable count between 2.13x104cfu/ml and 1.03x105cfu/ml. The yam flour purchased and examined microscopically showed the isolation of Staphylococcus aureus, S. Saprophyticus, E. coli, Klebsiella and Enterbacter sp for bacteria, and Fusarium and Aspergillus sp as fungi which are good mycotoxin producing fungi. The state of the market can also contribute to the increase in microbial load. Retailers should insist on getting well prepared yam flour with high hygienic practices from millers thereby ensuring well reduced load of microorganisms.
TABLE OF CONTENTS
Title
Page i
Certification
ii
Dedication iii
Acknowledge
iv
Table
of Contents v
List
of Tables ix
List
of Figures x
Abstract
xi
CHAPTER ONE
1.0
Introduction 1
1.1
Nutritional Composition Of Yam 3
1.2
Flour 3
1.3
Etiology Of Flour 4
1.4
Composition Of
Flour 4
1.5
Health Benefits Of Yam
Flour 5
1.6
Aim of Research 6
CHAPTER TWO
2.0
Literature Review 7
2.1Yam
Production in Nigeria 7
2.2
Yam Description 8
2.3
Geographic Regions 10
2.4
Cultivation Practices 11
2.5
Harvesting 11
2.6
Storage 12
2.7
Yam Plagues and Diseases 14
2.8
Uses of Yam 14
2.9
Production Process of Yam Flour 15
CHAPTER THREE
3.0
Materials and Method 17
3.1
Collections of Samples 17
3.2
Samples Labeling 17
3.3
Sterilization of Materials 17
3.4
Media Preparation 18
3.5
Isolation of Microorganisms from Samples 18
3.6
Enumerations of Fungi Isolate 19
3.7
Identification of Fungi Isolates 19
3.8
Bacteria Identification 19
3.9
Gram Staining 20
3.10
Biochemical Tests 20
3.10.1
Catalase Test 20
3.10.2
Coagulase Test 21
3.10.3
Indole Test 21
3.10.4
Oxidase Test 21
3.10.5
Citrate Test 21
3.10.6
Motility Test 22
3.10.7
Sugar Fermentation Test 22
3.10.8
Methyl-Red Test 22
CHAPTER FOUR
4.1
Result 24
CHAPTER FIVE
5.1
Discussion 32
5.2
Conclusion 33
5.3
Recommendation 34
References
LIST
OF TABLES
Table Title Page
1
Composition of Yam
9
2 Total Viable Bacterial Count from
Ahia Ohuru Market
25
3 Colony Count (Cfu/ml) For Market B
(Cemetery Market) 26
4 Colony Count (Cfu/ml) For Market C
(Umungasi Market) 27
5 The Mean Colony Count (Cfu/ml)
Between the Different Kinds of Yam Flour and Markets. 28
6 Identification and
Characterization of Bacteria Using Biochemical Test 2 9
7 Microscopic Appearance and
Macroscopic Appearance 30
8 The Frequency of Isolated Organisms
and Their Percentage 31
LISTS OF FIGURES
Figure Title Page
1. The production Process of
Yam Flour 16
CHAPTER
ONE
1.0 INTRODUCTION
The
word “yam” comes from Portuguese name or Spanish name, which both ultimately
derive from the Wolof word nyam, meaning "to sample" or
"taste", in other African languages it can also mean "to
eat" e.g. yam and nyama in Hausa (Mignouna, et al., 2003). Also yam
is the common name for some species in the genus and they are perennial
herbaceous vines cultivated for the consumption of their starchy tubers in
Africa, Asia, (Brand - Miller, et al., 2003).
Yams
are second to cassava as the most important tropical root crop. Yams are a
staple crop in many parts of Africa and Southeast Asia. In the South Pacific,
the yam is a significant food crop, accounting for the total dietary calorie
intake in the Kingdom of Tonga, Solomon Islands, and Papua New Guinea,
respectively. Besides their importance as food source, yams also play a
significant role in the socio-cultural lives of some producing regions like the
celebrated New Yam Festival in West Africa, a practice that has also extended
to overseas where there is a significant population of the tribes that observe
it. In some parts of Southeastern Nigeria, the meals offered to gods and
ancestors consist principally of mashed yam. Yams store relatively longer in
comparison with other tropical fresh produce, and therefore stored yam
represents stored wealth which can be sold all-year-round by the farmer or
marketer. In parts of Igbo land in Southeastern Nigeria, it is customary for
the parents of a bride to offer her yams for planting as a resource to assist
them in raising a family. There is no doubt that Nigeria produces yam in
abundance. In every state of the country, yam is available. It is estimated
that over 30% of the harvested yam tubers are lost as waste due to in
availability of processing and preservation mechanism. Even the traditional
processing method is out modeled and laborious but also grossly inefficient for
mass production to satisfy the teeming population and local demand and also
make room for the export market to earn scarce foreign exchange that is badly
needed at this time of the country. The consumption of yam cuts across
cultural, religious and demographic boundaries. A cherished delicacy when
served with well-prepared soup. Its processing shelf life, adds value to the
tubers, before being exported to enhance their economic value, reduces wastes
and cuts down the cost of transporting the product to longer distances compared
with the heavy wet tubers that are unprocessed (Adeleke, 2009).
However, yams can be processed into
less perishable products such as yam flour through a drying process (Jimoh and
Olatidoye, 2009). Yams are commonly consumed with sauces after boiling,
roasting, or frying. It is mashed or pounded into dough after boiling (Ferede et al., 2010; Omonigho and Ikenebomeh,
2000). There are indications that yam has great prospect of contributing to
closing the projected food deficit in Africa in the 21st century, if efforts
are made to identify and overcome the constraints to its production (FAOSTAT,
2005). Yam belongs to the semi perishable class of food due to its relatively
high moisture content and vulnerability to gradual physiological deterioration
after harvesting.
Infection of
yam by microorganisms could be at any stage in its growth, from seedling stage
through to postharvest (Amusa
et al., 2003). Yams are subjected to several diseases. Some fungal
species have been associated with the deterioration of yam tubers during
storage (Okigbo
and Ikediugwu, 2000). Therefore, to overcome the high deterioration rate of
yam, seasonal nature of yam production and also to serve as a preservative
method, yams are processed into yam flour or dried chips (Hounhouigan
et al., 2003).
1.1 NUTRITIONAL COMPOSITIONOF YAM
The nutritional
composition of yam is mainly starch but has varying levels
of proteins, lipids, minerals and most vitamins except Vitamin C (Huang
et al., 2007). The most preferable method of consuming yam is by
boiling and pounding because this gives it a soft texture and allows for easy
swallowing. In Nigeria, yam is also processed into various staple, intermediate
and end-products. In West Africa, yam could be processed into flour which is
used to prepare amala, boiled and eaten or pounded (Otoo
and Asiedu, 2009).
Yams are carbohydrate rich, staple tuber vegetables of West
African origin. Botanically it belongs to the family Dioscoreaceae, in
the genus, Dioscorea. Yams (Dioscorea
spp.) constitute an economically important staple food in tropical and
subtropical regions of the world. Yam tubers have high carbohydrate contents (Kouassi
et al., 2009) and are also sources of
proteins, fats, vitamins and minerals for many people. Production and
consumption of yam is predominant in West and Central Africa (Otegbayo
et al., 2005). Yam, Dioscorea spp.,
is the second most important root tuber crop in Africa, after cassava, with the
production of cassava being about 22% more than that of yam.
1.2 FLOUR
Flour is a powder which
is made by grounding cereal grains, other seeds or root (like cassava). Yam
flour is very evident in Africa and is used in the production of pounded yam.
It is the main ingredient of bread which is a staple food for many cultures, making
the availability of adequate supplies of flour a major economical and political
issue at various times of history. Wheat flour is one of the foods in European,
North America, and Middle East etc. and is one of the defining ingredients in
most of their styles bread and pastries. Maize flour has been important in
Mesoamerica cuisine since ancient times and remains a staple in Mexico and
parts of Central America. Rye flour is an important constituent of bread in
much of central Europe etc. (Anyaogu, 2013).
1.3 ETYMOLOGY OF FLOUR
The English word for “flour”
originally, a variant of the word “flower”. Both derived from the old French
“fleur” or flour, which had the literal meaning of “blossom” and a figurative
meaning of “finest”. The phase “fleur de farine” meant “the finest part of the
meal” since flour resulted from the elimination of coarse and unwanted matter
from the grain during milling.
1.4 COMPOSITION FLOUR
Flour
contains high proportion of starched, which are a subset of complex
carbohydrate also known as polysaccharides. The kinds of flour used in cooking
include all-purpose flour, self-rising flour and cake flour including bleached
flour. The higher the protein content, the harder and stronger the flour and
the more it will produce crusty and chewy breads, the lower the protein content
the softer the flour which is better for cakes and pie crusts.
Usually, yam
chips are sold out directly to consumers who in turn mill the chips into yam
flour, sieve through a 1 mm wire mesh and stir in boiling water to form “amala”
(Bankole and Mabekoje, 2004).
The quality of the dried yam chips varies from location to location and from
processor to processor (Mestres
et al., 2004). Though information on microbiological safety of the
dried chips from white yam has been reported, there is no information on the microbiological
quality of chips from water yam and the impact of the
milling practices on the microbiological quality and safety of the yam flour is
not available. This study was undertaken to investigate the microorganisms
associated with dried yam chips from white yam and water yam and examine the
influence of the milling process on the microbiological quality of the
resulting yam flour.
1.5 Health Benefits of Yam flour
Yam flour is a good source of energy; 100 g provides 118
calories. Its crunchy edible tuber chiefly composed of complex carbohydrates
and soluble dietary fiber.
Dietary fiber help reduce constipation, decrease bad (LDL)
cholesterol levels by binding to it in the intestines and lower colon cancer
risk by preventing toxic compounds in the food from adhering to the colon
mucosa. Additionally, being a good source of complex carbohydrate, it regulates
steady rise in blood sugar levels. For the same reason, yam flour recommended
as low glycemic index healthy food.
The tuber is an excellent source of B-complex group of
vitamins. It provides adequate daily requirements of pyridoxine (vitamin B6),
thiamin (vitamin B1), riboflavin, folates, pantothenic acid and niacin. These
vitamins mediate various metabolic functions in the body.
Fresh root also contains good amounts of anti-oxidant
vitamin; vitamin-C. Provides
about 29% of recommended levels per 100 g. Vitamin C play some important roles
as antigen, immune function booster, wound healing, and bone growth.
Yam flour contains small amounts of vitamin-A, and
beta-carotene levels. Carotenes convert into vitamin A inside the body. Both
these compounds are strong antioxidants. Vitamin A has many functions like
maintaining healthy mucus membranes and skin, night vision, growth and
protection from lung and oral cavity cancers.
Further, the tuber indeed is one of the good sources of
minerals such as copper, calcium, potassium, iron, manganese, and phosphorus.
100 g provides about 816 mg of Potassium.
Potassium is an important component of cell and body fluids which helps
controlling heart rate and blood pressure by countering hypertensive effects of
sodium. Copper is required in
the production of red blood cells. Manganese is used by the body as a co-factor
for the antioxidant enzyme, superoxide dismutase. Iron is required for red blood cell
formation.
Apart from food, yam
flour is mainly used for medicinal purpose for the sapogenins, a glycons of yam
saponin are important mainly because of their steroid structure. They are
precursors for the hemisynthesis of birth control pills (with progesterone and
estrogen) as well as similar hormones and corticosteroids). In Nigeria, some
yam species are use in herbal medicine for treatment of infertility in man.
Yams like higher plants have a complex photochemical profile.
1.6
Aim of Research
To
isolate, enumerate and identify microorganisms found in yam flour sold in Aba.
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