MICROBIAL CONTAMINATION OF ANIMAL PRODUCT

ABSTRACT

This study evaluated the microbial contamination of animal product (fat). From this study a total of six (6) bacterial strains and 3 (three) fungal strains were obtained. The total heterotrophic plate count (THPC) of the animal fat samples ranged from 3.6 × 105cfu/g to 4.4 × 105cfu/g with cattle fat sample giving the lowest mean count of 3.6 × 105cfu/g while pig fat sample had the highest mean count of 4.4×105cfu/g. The total coliform plate count (TCPC) from the animal fat samples ranged from 3.1 × 105cfu/g to 4.1 × 105cfu/g. The total fungal plate count (TFPC) from the animal fat samples ranged from 3.0 × 105cfu/g to 4.0 × 105cfu/g. It was observed that Escherichia coli is the most frequently occurring bacterial isolate from the pig and cattle fat samples with a percentage occurrence of (29.2%), followed by Staphylococcus aureus (25.0%), then, Salmonella sp. (20.8%), Bacillus sp. (12.5%), then Pseudomonas sp (8.3%) whereas Proteus sp. has the least percentage occurrence of (4.2%). In the same sequence, Aspergillus flavus is the most frequently occurring fungal isolate from the animal product (pig and cattle fat) sample with a percentage occurrence of (44.4%), followed by Aspergillus niger (33.3%) whereas Penicillium sp. has the least percentage occurrence of (22.2%).The presence of these microorganisms in the animal fat (pig and cattle) samples though not above the permissible limit (106cfu/g) is an indication of public health hazard and gives a signal of a possible occurrence of food borne intoxication and infection if not controlled. Statistical analysis showed that there were significant differences in mean count of the pig and cow fat samples at P< 0.05.

TABLE OF CONTENTS

Title Page                                                                                            i

Certification                                                                                       ii

Dedication                                                                                          iii

Acknowledgement                                                                              iv

Table of Contents                                                                               v

            List of Tables                                                                                                  vii  

            Abstract                                                                                                          viii

1.0                   CHAPTER ONE                                                                              

1.1                   Introduction                                                                                        1

1.2                   Types of Animal Fat                                                                           5

1.3                   Classifications of Animal Fats                                                           6

1.4                   Methods of Animal Fat Extraction                                                     9

1.5                   Uses of Animal Fat                                                                             10

1.6                   Factors That Promotes Microbial Growth in Animal Fat                        13

1.7                   Aim and Objectives                                                                            14

2.0                   CHAPTER TWO                                                                             

2.1                   Review of Related Literature                                                             15

2.1.1                Location of Salmonella in Poultry Fat Intended for Use in Pet

Food and the Influence of Fat’s Physical Characteristics on

Salmonella Prevalence and Growth                                                    16

2.1.2                The Survival of Various Pathogenic Organisms in Fats                  16

2.2                   Deterioration of Fats                                                                           16

2.2.1                Hydrolytic Deterioration of Fat                                                          17

2.2.2                Oxidative Deterioration of Fat                                                           17

2.2.3                Microbial Deterioration of Fat                                                           18

2.2.4                Health Effects                                                                                                 19

3.0                   CHAPTER THREE                                                                         

3.1                   Materials and Method                                                                         20

3.2                   Study Area                                                                                          20

3.3                   Collection of Samples                                                                        20

3.4                   Sterilization of Materials                                                                    20

3.5                   Preparation of Culture Media                                                             21

3.6                   Microbiological Analysis                                                                   21

3.7                   Inoculation and Isolation                                                                    21

3.8                   Purification of Isolates                                                                       21

3.9                   Identification of Bacterial Isolates                                                     22

3.9.1                Gram Staining                                                                                    22

3.9.2                Biochemical Test                                                                                22

3.9.2.1 Indole test                                                                                           22

3.9.2.2            Methyl red (MR)                                                                                 23

3.9.2.3 Voges proskauer (VP)                                                                        23

3.9.2.4 Hydrogen sulphide test (H₂S)                                                             23

3.9.2.5 Citrate test                                                                                           23

3.9.2.6 Urease test                                                                                          23

3.9.2.7 Catalase test                                                                                        24

3.9.2.8 Coagulase test                                                                                     24

3.9.2.9 Sugar fermentation test                                                                       24

3.9.2.10           Starch test                                                                                           25

3.10                 Identification of Fungal Isolates                                                         25

3.11                 Statistical Analysis                                                                             25

4.0                   CHAPTER FOUR                                                                           

4.1                   Results                                                                                                26

5.0                   CHAPTER FIVE                                                                              26

5.1                   Discussion, Conclusion and Recommendation                                  33

5.1.1                Discussion                                                                                           33

5.1.2                Conclusion                                                                                          35

5.1.3                Recommendation                                                                               35

References                                                                                          37

Appendix                                                                                            41

LIST OF TABLES

1.0                                                                   CHAPTER ONE

1.1       INTRODUCTION

Microbial contamination refers to non-intended or accidental invasion or introduction of microbes such as bacteria, fungi, viruses, or their toxins and/or by-products to humans, animals, plants, etc. Prominent changes for product contamination include: loss of viscosity and sedimentation due to depolymerisation of suspending agents, pH changes, gas production, faulty smell, shiny viscous masses etc. Fat is any substance of plant or animal origin that is non-volatile, insoluble in water, and oily or greasy to the touch. Fats are usually solid at ordinary temperatures, such as 25 °C (77 °F), but they begin to liquefy at somewhat higher temperatures. Basically, these are the by-products of the meat packing industry, made available as a result of the preparation of meat either for sale as meat percent or from the manufacture of meat product.

An animal product is any material derived from the body of an animal. Examples are fat, flesh, blood, milk, eggs, etc. Animal fats are especially stored under the skin and around specific organs, like kidneys. But muscular tissue also contains fat, producing more tender and tasty meat. Animal fat is a versatile, sustainable, and natural basis for many products. Worldwide, 172 million tonnes of vegetable and animal oils and fats are produced annually, from which approximately 25 million tonnes (14%) are estimated to be of animal origin (Sharma et al., 2013). In Europe, nearly 3 million tonnes of animal fats are produced annually. The main outlets for animal fats are feed (26%), oleo and soaps (22%), energy (19%), biodiesel (15%), and pet food (13%) (Sharma et al., 2013).

The utilization of meat by-products for food is often dependent on traditions, culture, and religion. Regulatory restrictions are also important, because some countries limit the use of certain by-products (such as fat) for food safety or quality reasons. The utilization of slaughter by-products can run through several pathways or industries depending on the type of raw material. For example, hides and skin are generally valorized by the leather or gelatin industry. Commonly used animal fats for biodiesel production via enzymatic route contains lard, lamb meat, beef tallow, chicken fat and animal fat mix (Colombani et al., 2006).

Animal fats can be categorized as edible and inedible. Typical edible fats are beef tallow, pork lard, goose or duck fat. Edible fats are used in foods while inedible fats are used as raw material in production. Edible meat by-products contain many essential nutrients (Jayathilakan et al., 2011). Animal fats play an important role in a balanced diet and in the manufacture of food products, contributing to texture and palatability. Edible animal fats are appreciated as multi-functional food ingredient and for their delicious taste and excellent baking and cooking properties. Edible animal fats are from animals specifically bred, reared, and slaughtered and are processed for human consumption in accordance with European Food Hygiene Regulations. Premium grade fat is cut from under the skin and from the abdominal cavity. It is purified, filtered and refined to produce high grade oils and fats. The major edible animal fats are tallow, derived from cattle, lard, which is derived from pigs, and poultry oils. They are a valuable source of concentrated energy and essential fatty acids needed for growth and development. Fat is a source of natural energy and is stored in adipose tissue as a fuel reserve (Colombani, 2006). It helps the body absorb the vitamins A, D, E and K and it contributes to the cell membrane structure. According to the World Health Organization/ Food and Agricultural Organization, in a healthy diet 15 to 35% of the daily calories should come from dietary fat. In fact, lard (rendered pig fat) has been suggested as an excellent alternative to cow’s milk fat in infant formula due to the fact that its fatty acid profile is close to that of breast milk, and lard is easily absorbed and digested (Colombani, 2006). The flavor-enhancing properties of bovine fat are the reason for its application as a frying agent, for example, frying fish and chips in Belgium and the United Kingdom. Lard has been used for hundreds of years as a major fat for cooking. Traditionally, it is used in bread or pastry making to assist the leavening process and to soften the crumb. The soft consistency and crystalline character make lard the most suitable shortening for pastry. At the usual lower mixing temperatures of pastry, lard retains its plastic properties, while other fats become too hard. Lard is used in the bakery industry for its color, flakiness, flavor, and tenderness. Lard and bovine fat are typically used for food in southern Europe and Asia (Colombani, 2006).

In spite of these useful biological functions, edible animal fats have, mistakenly, a negative reputation concerning health (supposed obesity and increasing cholesterol) mainly due to their content of saturated fatty acid. However, as all oils and fats, animal fats contain both saturated and unsaturated fatty acids. For example, lard contains 60% unsaturated fatty acids. One would hope that these recommendations are backed up with solid and clear evidence but unfortunately, we have to deal with fragile science with many publications indicating that animal fats are not harmful to human health (Siri-Tarino et al., 2010, Taubes, 2001). Edible animal fats consist of almost equal amounts of saturated and unsaturated fatty acids. Coconut oil, dairy butter, cocoa butter have higher amounts of saturated fatty acids than lard, tallow and poultry.

For decades, saturated fatty acid consumption is thought to increase cardiovascular risk because it increases plasma cholesterol levels. This view is now increasingly being challenged and new scientific data from multiple sources show that saturated fatty acid consumption per se is not associated with cardiovascular risk. It is true that cardiovascular risk is reduced when dietary saturated fatty acids are replaced by polyunsaturated fatty acids, but there is increasing evidence that replacing saturated fatty acids with largely refined carbohydrates does not benefit and even promote the risk of cardiovascular disease. Scientific meta-analysis published last few years show that no positive effects are found by replacing saturated fatty acids with monounsaturated fatty acids or largely refined carbohydrates (Siri-Tarino et al., 2010; Mozaffarian, 2006).

Animal fats are more and more utilized as bio-based raw materials in the oleochemical industry. The utilization of animal fats is considered very sustainable, and the European Commission has recognized rendering activity as highly sustainable for the use of animal fats as a raw material for the production of biodiesel. Animal fats are excellent raw materials for technical applications where thermal and oxidative stability are important, such as surfactants, lubricants, and biodiesel. Traditionally, animal fats are used for the production of soaps, candles, shampoos, and cosmetic products. Nowadays, oleochemical products made out of animal fats and oils are numerous and diverse (Siri-Tarino et al., 2010). Applications are found in personal care products (25%), lubricants, plastics, cleaning agents, coatings, glues, softeners, emulsifiers, additives, rubber, paper, paint, etc. Oleic acids, which are especially abundant in animal fats, are very suitable as a raw material for conversion to biopolymers. Animal fats may also be physically modified by fractionation to create an oleine fraction, e.g. lard oil. Lard oil is applied as a biolubricant or as rolling oil in the metal industry, due to its thermal stable properties. Chemically modified lard oil, for example by sulfonation, is applied as fat liquor to soften and lubricate leather. Recently, animal fats and oils have also been used to produce biodiesel or biofuel, as they are a sustainable source for the production of biodiesel.

Unless the animals are infected the meat of freshly slaughtered animals are generally sterile. The presence of microorganisms on post slaughtered carcasses is due to contamination occurring immediately before, during and after slaughter. The microbial contaminations of carcasses occur mainly during processing and manipulation during skinning, evisceration, processing at abattoir and retailers establishments. The main sources of meat contamination include; animal/carcasses source, on farm factors, transport factors, abattoir and butchers facilities, parasites and wild animals, meat van, abattoir and retail meat outlet workers.

1.2       TYPES OF ANIMAL FAT

·       Tallow

It is hard fat rendered from the fatty tissues of cattle that is removed during processing of beef. There are two types of tallow:

a. Edible tallow: The Codex Alimentarius recognizes standard for this as rendered from certain organs of healthy bovine animals. It is also known as dripping.

b. Oleo-stock: It is high grade tallow that is obtained by low temperature wet rendering of the fresh internal fat from beef carcass. It has light yellow color, mild pleasant flavor and free fatty acid content is less than 0.2%. Oleo-stock is also known by the synonym premier jus.

c. Inedible Tallow and Greases

These are the main inedible animal fats which are produced in many grades. Inedible tallow and greases produced by meat packing meat industry may contain either hog or beef fat. These are described in terms of their hardness. Fat with titer of 40 or greater than 40 are called as inedible tallow and those with titers less than 40 are called as greases. Titer is the measure of the temperature developed as a result of the heat of crystallization during cooling of melted fatty acids from the fat.

·       Lard

It is defined as the fat rendered from clean, sound edible tissues of hogs in good health at the time of slaughter. Its production is limited to certain killing and cutting fats from the hog. Depot fats such as those surrounding the kidney portion are examples of killing fats, since they are removed during the slaughtering operation. Cutting fats are those fats which are obtained when the hog is cut into its various wholesale or retail cuts (Hoenselaar, 2012).

a.     Caul Fat

It is the fatty membrane which surrounds internal organs of some animals, such as cow, sheep, and pigs also known as the greater omentum. It is often used as a natural casing. It is also known as Lace Fat.

b.     Leaf Fat

It is the fat lining the abdomen and kidneys of hog that used to make the lard.

c.     Rendered Pork Fat

It is the fat other than the lard, rendered from clean, sound carcasses or edible organs from hogs in good health at the time of slaughter, with certain parts of the animal specifically excluded. It includes bacon skins, fleshed skins, cheek meat trimmings, sweet pickle fats and fats obtained from skimming the rendered tanks.

·       Chicken Fat

It is the fat obtained (usually as a by-product) from chicken rendering and processing. It is high in linoleic acids, the beneficial omega-6 fatty acid. Linoleic acid levels are between 17.8-22.9%. It is used in the production of pet foods and bio-diesel. Chicken fat is one of the two types of animal fat referred as schmaltz, the other being goose fat.

·       Blubber

It is a thick layer of vascularized fat found under the skins of pinnipeds, cetaceans and sirenians

1.3       CLASSIFICATIONS OF ANIMAL FATS

Animal fats are classified according to the presence and number of double bonds in their carbon chain. Saturated fatty acids (SFA) contain no double bonds, mono-unsaturated fatty acids (MUFA) contain one, and polyunsaturated fatty acids (PUFA) contain more than one double bond.

·       Saturated Fat

A saturated fat is a type of fat in which the fatty acid chains have all or predominantly single bonds. A fat is made of two kinds of smaller molecules: glycerol and fatty acids. Fats are made of long chains of carbon (C) atoms. Some carbon atoms are linked by single bonds (-C-C-) and others are linked by double bonds (-C=C-).  Double bonds can react with hydrogen to form single bonds. They are called saturated, because the second bond is broken and each half of the bond is attached to (saturated with) a hydrogen atom. Most animal fats are saturated. The fats of plants and fish are generally unsaturated (Jayathilakan et al., 2011).Saturated fats tend to have higher melting points than their corresponding unsaturated fats, leading to the popular understanding that saturated fats tend to be solids at room temperatures, while unsaturated fats tend to be liquid at room temperature with varying degrees of viscosity (meaning both saturated and unsaturated fats are found to be liquid at body temperature). Various fats contain different proportions of saturated and unsaturated fat. Examples of foods containing a high proportion of saturated fat include animal fat products such as cream, cheese, butter, other whole milk dairy products and fatty meats which also contain dietary cholesterol.  Certain vegetable products have high saturated fat content, such as coconut oil and palm kernel oil.  Many prepared foods are high in saturated fat content, such as pizza, dairy desserts, and sausage (Hoenselaar, 2012).

Some common examples of fatty acids:

a.     Butyric acid with 4 carbon atoms (contained in butter )

b.     Lauric acid with 12 carbon atoms (contained in coconut oil , palm kernel oil , and breast milk)

c.     Myristic acid with 14 carbon atoms (contained in cow's milk and dairy products)

d.     Palmitic acid with 16 carbon atoms (contained in palm oil and meat)

e.     Stearic acid with 18 carbon atoms (also contained in meat and cocoa butter)

·       Unsaturated Fat

An unsaturated fat is a fat or fatty acid in which there is at least one double bond within the fatty acid chain. A fatty acid chain is monounsaturated if it contains one double bond, and polyunsaturated if it contains more than one double bond (Colombani, 2006).Where double bonds are formed, hydrogen atoms are subtracted from the carbon chain. Thus, a saturated fat has no double bonds, has the maximum number of hydrogens bonded to the carbons, and therefore is "saturated" with hydrogen atoms. In cellular metabolism, unsaturated fat molecules contain somewhat less energy (i.e., fewer calories) than an equivalent amount of saturated fat. The greater the degree of un-saturation in a fatty acid (i.e., the more double bonds in the fatty acid) the more vulnerable it is to lipid peroxidation (rancidity). Antioxidants can protect unsaturated fat from lipid peroxidation (Ratnayake and Galli, 2009).

·       Poly-unsaturated fat

Poly-unsaturated fats are fats in which the constituent hydrocarbon chain possesses two or more carbon–carbon double bonds. Poly-unsaturated fat can be found mostly in nuts, seeds, fish, seed oils, and oysters. "Unsaturated" refers to the fact that the molecules contain less than the maximum amount of hydrogen (if there were no double bonds). These materials exist as cis or trans isomers depending on the geometry of the double bond (Willett, 2007).

Saturated fats have hydrocarbon chains which can be most readily aligned. The hydrocarbon chains in trans fats align more readily than those in cis fats, but less well than those in saturated fats. In general, this means that the melting points of fats increase from cis to trans unsaturated and then to saturated. See the section about the chemical structure of fats for more information.

The position of the carbon-carbon double bonds in carboxylic acid chains in fats is designated by Greek letters. The carbon atom closest to the carboxyl group is the alpha carbon, the next carbon is the beta carbon and so on. In fatty acids the carbon atom of the methyl group at the end of the hydrocarbon chain is called the omega carbon because omega is the last letter of the Greek alphabet. Omega-3 fatty acids have double bond three carbons away from the methyl carbon, whereas omega-6 fatty acids have a double bond six carbons away from the methyl carbon. The illustration below shows the omega-6 fatty acid, linoleic acid (Pala et al., 2001).

While it is the nutritional aspects of poly-unsaturated fats that are generally of greatest interest, these materials also have non-food applications. Drying oils, which polymerize on exposure to oxygen to form solid films, are polyunsaturated fats. The most common ones are linseed (flax seed) oil, tung oil, poppy seed oil, perilla oil, and walnut oil. These oils are used to make paints and varnishes.

1.4       METHODS OF ANIMAL FAT EXTRACTION

The process of extraction of animal fats from raw material is termed melting or rendering. “Rendering” is an old word, which can mean different things to different people. In its simplest form, rendering means “to render open” (or split) – by heat processing – raw material into a solid(proteins) and a liquid (fat, liquid at elevated temperatures). While in theory, this covers all aspects of animal by-product processing, in the practical world rendering has, in many cases, become synonymous with the processing of inedible animal by-products. However, rendering can also be used to describe the processing of edible grade by-products, and in these circumstances edible rendering should be clearly stated, although many still prefer to use the alternative term, “fat processing”. There are two main systems of rendering, described as either “wet” or “dry” systems, with the latter being further divided into natural fat and added fat systems.

·       Wet melting /rendering

For wet melting, the heat applied is only enough to melt the fat, and both the “protein” and “fat” still contain water after decanting. The water is evaporated or separated in subsequent steps, with the final products being protein meal and rendered animal fat. Wet melting is preferably applied for the processing of edible fat-rich material, like cutting fat, back fat, and leaf fat. The main disadvantage of wet melting is that water is added by means of steam injection and much water has to be removed by physical separation and drying. On the other hand, wet melting applies less heat energy (up to 95^oC), which results in a higher quality fat and protein compared to dry rendering.

·       Dry melting /rendering

In dry rendering, the raw material is boiled in its own fat or added fat until most of the water is evaporated. After evaporation of the water, physical separation takes place like sieving, decanting and pressing, to separate and purify the components, protein and fat. Dry rendering can be characterized as a frying process, usually with temperature between115^oC and 135^oC. There are many hybrid processes of the wet and dry methods used in the industry and these can be most simply described in terms of system type, fat level, and process condition (Doppenberg and Vander, 2010).

1.5       USES OF ANIMAL FAT

•       Making Schmaltz

Schmaltz is a Jewish delicacy that is simply made using chicken fat during the rendering process. It is used in a wide variety of dishes to add richness and flavor.

•       Pastries

Animal fat is used to make a crispy, flaky pastry which adds flavor to foods. Some gamier fats such as bear may add a meaty or gamey flavor to crust which is used in making a savory meat pie or an apple pie. Visceral fats from any animal, the deep fats found around the organs, may best be rendered separately because it typically has very little flavor and is great for pastries. Beef fat, pork fat and goat fat are also great for sweet pastries (Kaminsky and Peter, 2005).

•       Savory Recipes

Tallow is used in preparing beef stew which adds flavor and richness. Chicken soup is best when tossed in schmaltz (Julie, 2014).

•       Deep Frying

Animal fats have high taste and lower temperature smoking point suitable for deep frying. These fats do not smoke at lower temperatures. Fats such as butter or bacon grease make them poor choices for deep frying because they smoke at low temperatures. Duck fat is considered a delicacy for frying. Other more available fats such as lard, tallow, goat and venison all make good frying grease. Animal fat is typically going to have a lower smoke point than most vegetable oils (Katragadda et al., 2009).

•       Waterproofing

Animal fats provide the best waterproofing property. I’m not sure what the difference is but it just seems to provide better waterproofing, especially for boots, and it seems to last longer, too.

•       Fire Starter

Though animal fat goes rancid fairly quickly if not refrigerated, it is still safe to eat but it tastes like crap. Animal fat therefore can be used to make fire. If you have fat that is gone rancid but you do not want to waste it, use it to make fire starters. Dip a tampon, a cotton ball or a piece of tinder in the fat and watch it burn.

•       Soap Making

Animal fat gives a good, hard bar of soap that will not turn to glop as soon as it gets wet. Tallow (beef fat), goat fat or lard (pig fat) are often used by experienced soap makers. There is no reason why elk, moose or other large animals could not be used; these three fats are just more readily-available. You can use fats from some plants but the curing process takes months to years whereas soap made with animal fat is ready to use in about 3 weeks.

•       Candle Making

You can use animal fat to make simple, functional candles. They will not smell pretty but they will keep the lights on. Tallow is good for this because it gets good and hard. Lard works but it is a lot softer. Just place the wick in a jar so that it goes all the way to the bottom, then pour melted tallow in. You’ll need to secure the wick so that it stays in the middle until the tallow gets hard. (Doppenberg and vander, 2010).

•       Skin Care

The lipids found in animal fats closely mimic the oils in our skin and people who are getting back to the “old” way of doing things are discovering that animal fats make a great base for soaps, lotions and balms for that very reason. They are easily absorbed and free of the chemicals and toxins found in commercial products. They also make your skin soft and your hair shiny, though be careful using it on your hair; you will have to wash it a few times to get the grease out.

•       As a lip balm

EPIC's beef tallow is wonderful for chapped and dry lips. Loaded with healthy saturated fats, our 100% grass-fed beef tallow is a pure alternative that will outlast and outperform mass produced lip balm brands that often contain sketchy ingredients.

•       As a makeup remover

Animal fats gently remove mascara and other makeup while simultaneously cleaning your skin and moisturizing your face. All without the use of harsh chemicals or other petroleum-derived ingredients.

•       As a butter substitute in baking

Classically-trained chefs across the globe use animal fats such as pork fat to create the flakiest pie crusts on the planet. Pork Fat can easily replace butter in most baking recipes and has a substitution ratio of 1:1. Take your baking to new realms of glory (Davidson and Alan, 2002).

1.6       FACTORS THAT PROMOTE MICROBIAL GROWTH IN ANIMAL FAT

Microorganisms are similar to more complex organisms in that they need a variety of materials such as animal fats to function and accomplish two primary goals--supply enough energy to manage their processes and extract building blocks to repair themselves or procreate. In addition to what they take in, microorganisms also thrive in particular environments. These environments vary as much as the organisms do themselves, and even the amount and distribution of elements in any particular environment can be very important (Doppenberg and vander, 2010). All microorganisms need food. The food sources can vary, but the organisms primarily extract carbon and nitrogen from substances such as proteins, fats and carbohydrates. Some microorganisms seek out and absorb such particles. Others may perform chemical reactions with surrounding elements such as carbondioxide to gain what they need, while still others can produce their own simple sugars through photosynthesis similar to plants. Nitrogen, which is used to synthesize proteins, can be taken from the surrounding atmosphere or from other organic matter (Mozaffarian et al., 2006).

·       Temperature

In general, the higher the temperature of animal fat, the more easily microorganisms can grow up to a certain point. Very high and very low temperatures both obstruct the enzyme processes in animal fat which microorganisms depend on to survive, but individual species of microorganisms have grown to prefer different levels of temperature (Maki, 2009). Scientists usually divide them into three different groups: psychrophiles, mesophiles and thermophiles. Psychrophiles prefer temperatures from 0 to 5 degrees Celsius; mesophiles like it in the middle, 20-45 degrees Celsius; and thermophiles like it hot, thriving in temperatures around or above 55 degrees.

·       Moisture

The free water activity in animal fat is vital to microorganisms for their cells to exchange materials and for their metabolic processes. All microorganisms require some level of water, but a few can survive in low-moisture conditions by conserving all the water they find and by staying in a moisture-rich environment (Abulude et al., 2007). As a general rule, though, the more moisture, the more microorganisms there will be found.

·       pH Levels

Microorganisms also prefer a certain pH level in the animal fat substance or environment in which they grow--that is, they prefer to have particular acidic qualities in their surroundings. Most microorganisms, including most human pathogens, are neutrophils, organisms that prefer a neutral pH level (Aranceta and Pérez, 2012). Some like high pH levels, but most often, if conditions are too acidic, then the organism's enzymes break down.

·       Oxygen

Many microorganisms present in animal fat require oxygen for their growth and metabolism. In terms of their oxygen needs, bacteria are classified as aerobic, facultative anaerobic, and anaerobic. Aerobic bacteria require oxygen for growth. Anaerobic bacteria do not need any oxygen to grow. To some anaerobic bacteria, such as Clostridium botulinum, the presence of oxygen inhibits their growth and toxin production. Facultative anaerobic bacteria prefer using oxygen for metabolism, but they can also grow without any oxygen.

1.7       AIM AND OBJECTIVES

The aim of this study is to determine the microbial contaminants associated with animal fats (Cattle and Pig).

The objectives include:

1. To isolate and identify bacterial isolates associated with animal fat (Cattle and Pig)
2. To isolate and identify fungal isolates associated with animal fat (Cattle and Pig).
3. To determine the percentage occurrence of the isolates.

Buyers has the right to create dispute within seven (7) days of purchase for 100% refund request when you experience issue with the file received. 

Dispute can only be created when you receive a corrupt file, a wrong file or irregularities in the table of contents and content of the file you received. 

ProjectShelve.com shall either provide the appropriate file within 48hrs or send refund excluding your bank transaction charges. Term and Conditions are applied.

Buyers are expected to confirm that the material you are paying for is available on our website ProjectShelve.com and you have selected the right material, you have also gone through the preliminary pages and it interests you before payment. DO NOT MAKE BANK PAYMENT IF YOUR TOPIC IS NOT ON THE WEBSITE.

In case of payment for a material not available on ProjectShelve.com, the management of ProjectShelve.com has the right to keep your money until you send a topic that is available on our website within 48 hours.

You cannot change topic after receiving material of the topic you ordered and paid for.