ABSTRACT
Five samples of powdered milk collected from retailed shops in the market were analysed for microbial quality. The milks were tested for total aerobic count (TAC), coliform counts and various foodborne pathogens. TACs ranges from 2.98 x 103 to 3.64 x 103 cfu/ml. Escherichia coli were detected in 25% of the samples. Bacillus cereus was confirmed in 27% of the samples. Staphylococcus aureus was detected in 27% of the samples. Lactobacillus was detected in 15.5% of the samples. fumigatus, and mucor sp was observed for the fungi isolates. An apparent relationship between high aerobic count detection of coliforms and presence of food- borne pathogens was observed. These findings suggest that most of the powdered milk sold by retailers may constitute sources of bacterial food poising, consequently public health hazards. The need for improvement and maintenance of good hygienic practices by food handlers in this country is emphasized.
TABLE OF CONTENTS
Title page i
Certification ii
Dedication iii
Acknowledgement iv
Table of contents v
List of Tables ix
Abstract
CHAPTER ONE
1.1 INTRODUCTION 1
1.2 Aims
and Objectives 4
CHAPTER TWO
LITERATURE REVIEW
2.1 Milk 5
2.2 Factors Affecting
Milk Production 5
2.3 Breed 6
2.4 Dry period 6
2.5 Age and body weight
at calving 6
2.6 Lactation number 7
2.7 Pregnancy 7
2.3 Milk Nutrition 9
2.3.1 Nutritional significance 10
2.4The quality of milk 10
2.5 Types of Milk 10
2.6 Powdered milk 11
2.6.1 Salting 11
2.6.2 Dehydrating 11
2.6.3 Freezing 12
2.6.4 Use of
Dry milk 12
2.7 Determination of Microbial Quality of Liquid
Milk 12
2.8 Milk Fermentation 13
2.9 By Products of Milk 14
2.9.1 Cheese 14
2.9.2 Ice Cream 16
2.9.3 Buttermilk
(Cultured) 17
2.9.4 Yogurt 17
2.10 Processing the Powdered Milk 18
2.11 Micro Flora of Dried
Milks 19
2.12 Contamination of Food 19
2.12.1 Sources
of Milk Contamination 20
CHAPTER
THREE
MATERIALS AND METHODS 25
3.1
Collection of Samples 25
3.2. Preparation of Media 25
3.3 Sample Analysis and
Identification 25
3.4 Viable count 26
3.5 Characteristics of
Bacterial Isolates 26
3.5.1 Gram stain 26
3.6 Biochemical
Test 26
3.6.1 Oxidase test 26
3.6.2 Catalase test 27
3.6.3 Coagulase test 27
3.6.4 Citrate Test 27
3.6.5 Lysine test 27
3.6.6 Indole
test 28
3.6.7 Hydrogen sulfide (H2S) 29
3.6.8 Motility test 29
3.6.9 Voges Proskauer Test 29
CHAPTER
FOUR
CHAPTER
FIVE
5.0 DISCUSSION, CONCLUSION AND
RECOMMENDATION
5.1 Discussion 36
5.2 Conclusion 38
5.3 Recommendations 38
References
LIST
OF TABLES
Table
4.1: Morphorlogical and biochemical characteristics of
bacterial isolates 31
Table
4.2: Total Viable Count (cfu/ml)32
Table
4.3: Percentage occurrences of bacterial isolates from
powdered milk samples 33
Table
4.4: Total Count 34
Table 4.5 Fungi Count 35
CHAPTER
ONE
1.1 INTRODUCTION
The world is faced with a problem of food shortage
and milk products are considered as a partial solution for this problem in
developing countries. But these products are vulnerable to spoilage by certain
to human beings. The number and type of microorganisms present in foods are
influenced by mans’ factors, that include the general environment for which
food was obtained, the microbiological quality of the food in its processed
state, the sanitary conditions under which the product was handled and
processed and finally the adequacy of subsequent packing. handling and storage conditions
in maintaining the flora at low level (Jay.l986).microbial load must kept as
loss as possible and the main sources of contamination must he importantly known.
Numerous studies have documented that powder milk could contaminated by
bacteria. In national institute of public health it was reported that on spray
drying of milk artificially contaminated with Bacillus cereus spores
(ln’t veld. 1993).
Study performed in New Zealand for sample of milk
powder revealed that it’s contaminated by Bacillus licheniformis and
Bacillus subtilis (Ronimus et al..
2006). Milk powder is made by removing water from liquid milk. Removing
water is necessary to reduce water activity for the prevention of microorganism
growth. Dry milk is used to produce such products as yogurt, cheese; ice cream
and whey powder. There are a multitude of products derived from dried milk.
Moreover, the advantages of dry milk over liquid milk are better keeping
quality, less storage space and low shipping costs. Powdered infant formula
(PIF) is readily available, as either a supplement to or replacement for breast
milk. PIF is heat-treated during processing but. Unlike liquid formula
products, it is not subjected to sufficient treatment to make the final
packaged product commercially sterile. While PIF may not be commercially sterile,
its production is undertaken using rigorous hygienic precautions coupled with
monitoring of the process environment and finished product by the manufacturer.
These activities assist in reducing the microbial load of PIF Salmonella and
Cronobacter sakazakii (formerly classified as Enterohacter sakazakii) have been
identified as the organisms of greatest concern with PIF (FAO/WHO. 2004 &
2006). To date, no cases of illness in infants linked to the consumption of
infant formula have been reported in Australia. Salmonella is a well-known food
borne human pathogen. Overseas. at least six reported outbreaks of
salmonellosis involving approximately 250 infants were associated with PIF
between 1985 and 2009(Appendix I). Most of the outbreaks involved unusual
Salmonella serotvpes. hich assisted in outbreak investigations. It has been
suggested that outbreaks and sporadic cases of salmonellosis due to PIF are
likely to he under-reported (FAO/ WHO. 2006). (sakazakii is an opportunistic
pathogen emerging as a public health concern. Considerable progress has been
made in understanding the ecology of this organism, but there is still little
known about its pathogenesis and virulence factors. Infections from C. sakazakii
have been reported as both sporadic cases and outbreaks. The primary
manifestations of C. sakazakii infection in infants include meningitis sand
bacteraemia, which tend to vary with age.
Reported fatality rates of C. sakazakii infections
in infants vary considerably with rates as high as 50% reported in at least one
outbreak (Appendix 1). In addition, a portion of surviving infants has
permanent disabilities such as retardation and other neurological conditions.
In some of these outbreaks and cases, PIF was established as the source of the
infections. In many, the exact source could not he determined. Ten studies
determining the microbiological quality of commercial powdered infant formula
were identified by a literature search. C. sakazakii was detected in seven of
the studies with prevalence rates ranging from 0.5% to 25% (Appendix 2). Three
of’ the studies also performed quantitative tests and C. sakazakii was detected
at levels from 0.36 cfu/100g up to 66 cfu/100g (Muytjens et al.. 1988:Nazarowec-White & Farber. 1997; Zink. 2003).
Salmonella was tested in five surveys and %as not detected in any of the
formula tested (Estuningsih et al. 2006: Iversen & Forsythe. 2004: Muytjens
et al. 1988: Thompson. 2010).To date. there is limited public information in
Australia on the microbiological quality of powdered infant formula. One PIE
sample from Australia tested positive for C. sakazakii in the survey reported
by Muytjens et al. (1988) at the level of 0.36 cfu/100g. However, no data was provided on the
number of samples actually taken from Australia in that survey and it is likely
that this result does not reflect recent changes in the production of PIF that
are likely to influence the microbiological quality of PIF.
The most recent survey conducted by the South
Australian Government did not find any pathogens in the twenty samples tested
(Thompson. 2010). In 2008, a suspected case of food borne illness initially
linked to infant formula took place in South Australia. Further investigation
found that the illness was not actually due to the product. but due to poor of
hygiene and improper handling of reconstituted infant formula. The incident,
however, highlighted the lack of available data on microbiological quality of
infant formula in Australia. Thus, a survey was conducted to gather information
on the microbiological quality of’ these products sold in NSW. The information
collected on the microbiological quality of powdered infant formula will
supplement the communication message on the safe handling of powdered infant
formula that was developed for consumers and caregivers and is available on the
NSW Food Authority website. Milk and dairy products form a significant part of
the human diet. They are rich sources of nutrients such as proteins, fats, vitamins
and minerals: ironically. It is because of this that these products are
susceptible to rapid microbial growth. In some instances, this microbial growth
may be beneficial, while in others it is undesirable. Dairy products are
vulnerable to spoilage or contamination with pathogens or microbial toxins:
therefore, the microbiology of these products is of key interest to those in
the dairy industry. Food spoilage is an enormous economic problem worldwide.
Through microbial activity alone, approximately one-fourth of the world’s food
supply is lost. Milk is a highly nutritious food that serves as an excellent
growth medium for a wide range of microorganisms. The microbiological quality
of milk and dairy products is influenced by the initial flora of’ raw milk, the
processing conditions, and post—heat treatment contamination. Undesirable
microbes that can cause spoilage of dairy products include Gram-negative
psychrotrophs, coliforms, lactic acid bacteria, yeasts, and molds. In addition,
various bacteria of public health concern such as Salmonella spp., Lisieria monocytogenes, Camphylobacter
jejuni, Yersinia enterocolitica,
pathogenic strains of Escherichia coli and
enterotoxigenic strains of Staphylococcus aureus may also he found in
milk and dairy products. For this reason, increased emphasis should he placed
on the microbiological examination of milk and dairy foods. Microbiological
analyses are critical for the assessment of quality and a safety, conformation
with standards and specifications, and regulatory compliance.
1.2 AIMS AND OBJECTIVES
To evaluate the microbial load of powdered milk
To determine the presence of microbial pathogens in
powdered milk samples
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