ABSTRACT
Ice-cream
is a nutritionally enriched diary products consumed by all age groups most
especially children particularly in summer as well as throughout the year. Its
microbial quality has always been crucially important to the public health. The
present study was constructed to assess the bacteriological quality of ice
cream sold in Umuahia. A total of 14 samples were randomly purchased from the
fast food joint, supermarket, school, market and street hawkers differentiated in 2 categories: industrially produced ice cream (IND1-IND7) and locally
produced ice cream (LP1-LP7). The total heterotrophic count range from
3.0x10³-2.0x106 (cfu/g) with industrially variety (IND3-IND4) recording no
bacterial growth and also some lowest count while locally produced ice-cream
has the highest count. The total staphylococcus ranged from 1.0x10² (cfu/g) in
the industrially produced variety (IND4) to 3.0x10³ (cfu/g) in the locally
produced variety (LP5). For E. coli count, the range was from 1.0x10²
(IND2)-2.0X105 (LP5) (cfu/g) in both industrially produced and locally
produced. The Lactobacillus count
range from 1.0x10² (LP1)-1.0X104 (LP4) (cf/g). Total isolates were eight
bacteria (Staphylococcus aureus,
Lactobacillus spp., Streptococcus
spp., Proteus spp.,Escherichia coli, Klebsiellae and Pseudomonas
aeroginosa). Lactobacillus has
the highest incidence (7) with the percentage of 50% while Proteus spp, Klebsiella, Pseudomonas aeroginosa had the least
incidence and percentage of (1) 7.1%, (2) 14.2% and (2) 14.2% respectively. The
total heterotrophic count was further subjected to a t- test statistical
analysis which showed no significant difference (p<0.05;) between comparing
the bacteriological quality of locally produced ice cream and industrially
produced ice cream fall into the same categories. Since in the bacteriological
count of ice cream industrially produced, 2 out of 7 products show no bacteria
growth which implies that if adequate preparation that is standard process are
used it is possible for industrially produced ice cream to be safe to health
and better than locally produced ice cream. The presence of pathogenic organism
in the ice cream sample should be viewed
with concern by the consumes, producers, ice cream manufacturing industries and
the government since food poisoning by Staphuyloccocus
Aureus, Bacillus spp, is possible
through consumption of contaminated ice cream.
TABLE OF CONTENTS
Title page i
Certification ii
Dedication iii
Acknowledgement iv
List of tables v
CHAPTER ONE
1.0
Introduction 1
1.1 Aims and objectives 4
CHAPTER TWO
2.0 Literature review 5
2.1 Location of microbes 6
2.2 Manufacture of ice-cream 7
2.3 Microorganisms in
ice-cream 7
2.3.1 Bacteria 8
2.3.2 Mould 8
2.3.3 Yeast 8
2.4 Microbial community of
ice-cream 8
2.5 Hygienic and microbial
aspects 9
2.6 Major diseases transmitted
through ice-cream 13
2.7 Microbiology of ice-cream 15
CHAPTER THREE
3.0 Materials and Method 17
3.1 Study area 17
3.2 Experimental design 17
3.3 Sample collection 17
3.4 Sterilization of materials 18
3.5 Media 18
3.6 Preparation of serial
dilution 19
3.7 Bacteriological
examination 19
3.8 Characterisation and
identification of bacteria isolates 20
3.9 Gram staining 20
3.9.1 Catalase test 21
3.9.2 Coagulase test 21
3.9.3 Oxidase test 21
3.9.4 Citrate test 22
3.9.5 Motility test 22
3.9.6 Indole test 22
3.9.7 Statistical analysis 23
CHAPTER FOUR
4.0 Results 24
CHAPTER FIVE
5.0 Discussion 33
5.1 Conclusion 36
5.2 Recommendation 37
References
Appendix
CHAPTER ONE
1.0
INTRODUCTION
Milk is a complex biological fluid and by its nature,
a good growth medium for many microorganisms. As a result of the specific
production, it is impossible to avoid contamination of milk with
micro-organisms therefore the microbial content of milk is a major feature in
determining its quality (Rogelj, 2003). Bacterial contamination of raw milk can
originate from different sources: air, milking equipment, feed, soil, faeces
and grass (Coorevits et al., 2008). Milk is an
opaque white liquid produced by the mammary gland of female mammals. It
provides the primary source of nutrition for newborn mammals before they are
able to digest other types of food. The exact components of raw milk vary by
species, but it contains significant quantity of saturated fat, protein and
calcium as well as vitamin C. Cow milk has a pH ranging from 6.4 to 6.8 making
it slightly acidic. Several animals produce milk for human consumption,
although the cow is by far the most important in commercial terms (Adams and
Moss, 1999). The milk is perishable thereby necessitating it’s immediate
consumption as fresh milk and can be processed into other products like
ice-cream, yoghurt, cheese, butter which have improved keeping qualities. Ice
cream is a product of milk which consists of milk, sweetening and stabilizing
agents together with flavoring and colouring matter (Malou and Uzochukwu, 1999).
It is a product that has wide patronage from infants, youth, adolescent and
adult (Akinuli, 1998). There are numerous variables that must be controlled
accurately during processing to obtain a high quality ice cream with the
required taste, flavor, viscosity, consistency and appearance. Handling and
storage conditions are some of these variables because they affect the
physical, chemical and microbial quality of the product. The methods employed
in the sales of ice cream are of different categories. It could be sold in open
containers at retail outlets or in packages which may then be distributed manually
in satchets, scoops or cones across the counter (Marshall and Arbuckle, 1996) (Warke et al., 2000); (Champagne et al., 1994) and (Daniels et al., 2002). Most ice creams become
contaminated with microbes during production, transit, and preservation.
Disease outbreak in many countries of Asia, Europe, and North America is as a
result of consumption of ice cream contaminated with microbial pathogens during
the processing stage (Chung, 1996). In Previous reports, high microbial loads
in ice cream samples obtained from patisseries in Turkey were observed (Digrak
et al., 2000; Evrensel and Gunes,
1998; Kivanc et al., 1994). The
consumption of ice-cream is higher among children of vulnerable age groups
therefore there is a need to maintain a high microbiological safe standard. A
relatively low storage temperature and pasteurization step during its
processing are considered to eliminate most of the pathogenic microorganisms.
However, the addition of contaminated ingredients, improper handling and the
use of improper storage temperatures are factors that contribute to the
potential hazard of the finished products especially during processing and after
pasteurization processes. This is particularly of interest during soft ice
cream preparation since the point of sale happens to be its final stage of
production (Verma, 1992).
Other possible sources of
microorganisms in ice–cream have been reported to include raw materials used
for the composition of ice-cream mix such as separated milk and milk powder
cream, flavoring and coloring substances and stabilizers (Gomez, 1999) and from
air during processing (Pelzer and Michael, 2000). Food spoilage is a
predominant problem in African countries, Nigeria inclusive. It is generally
stored by refrigeration, but the original taste and flavor does not last very
long. Proper handling and storage of ice-cream helps to prevent its spoilage
and the incidence of food borne illness, thereby increasing its shelf life. Ice
cream is considered a popular product consumed particularly in summer as well
as throughout all year and continues to be a dominant interest of large
segments of the population (Mann, 1988). It is a combination of milk, sweetener,
stabilizer, emulsifier and flavoring agents, egg products, coloring additives
and hydrolyzed products of starch (Marshall and Arbuckle, 1996). Many studies
have measured the sensory properties of ice cream to evaluate the relationship
among various ingredients and sensory characteristics such as flavor and
texture (Hyvönen et al., 2003). The
body and texture characteristics are closely associated and are important in
influencing consumer acceptance of ice cream and related products.
Microorganisms are transmissible to humans through milk and milk products
(Samarzija et al., 2012). The
microbiological quality of ice cream can be low, as it is a good growth-medium
for microbes (Kanbakan et al., 2004),
especially as a hawking product. Historically, ice cream has been responsible
for numbers of outbreaks of food borne illness (Nichols et al., 1995).
The
source of microbial contamination can be at various stages of manufacture from
humans and environmental sources (Chukuezi, 2010). The high content of nutrients
like lactose of ice cream, proteins and its neutral pH (6–7) makes it an
excellent growth medium for microbes, some of which may cause serious diseases
and outbreaks like cholera, typhoid and bacillary dysentery in human beings
(Ahmed et al., 2009 and Lee et al., 2009). Coliforms (fecal types)
were historically used as indicator microorganisms to serve as a measure of faecal
contamination, and thus potentially of the presence of enteric pathogens in
food (Osamwonyi et al., 2011).
Although some of these coliforms are not pathogenic, their presence indicates
possible faecal contamination and the corresponding presence of intestinal
pathogens responsible for a variety of diseases (Cakir et al., 2002). Coliform organisms are commonly used to reflect hygienic
statistics of final products and effectiveness of hygienic practice in
production. Bacteriological quality of ice cream reflects the hygienic practice
in production and is an indication of food safety.
1.1 AIMS
AND OBJECTIVES
i.
To isolate, identify and characterize the microorganisms of different ice cream
samples sold in Umuahia.
ii. To determine bacteriological
quality of ice-cream offered for public consumption in Umuahia and its
potential to pose risk to the public.
iii. To compare the bacteriological
quality of industrially produced and locally produced ice cream sold in
different areas of Umuahia.
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