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ABSTRACT
This research study titled, “Isolation And Characterization Of Fungi Associated With Baked Cake” is aimed at identifying and characterizing fungi contained in baked cake. The study was carried out at the Biology Laboratory of Ken Saro-Wiwa Polytechnic Bori. The fungi associated with baked cake can come from the air, contaminated packaging materials and other sources. In this study, a total of fungal isolates on the colonial counts was 64 representing; 9 species identified from unexposed cake samples and 14 species from exposed cake samples. For each cake sample, the culture and sub-culturing methods, pour plating and spread plating were applied. The isolation and identification based on morphological characterization includes colony’s structure and profiles identified by slide culture technique and primary Keys identification. Meanwhile the plates were under observation for growth rate of 64 isolated fungi after five(5) days at 25°C. The findings showed that the most dominant fungal genera arranged in the baked cake were Penicillium sp. Aspergillus sp., Mucor and Rhizopus spp and Trichorderma spp. respectively. Conclusively the colony’s growth rates was adapted with the previous results of counting colonies. Considering the time-rate relationship amongst the 23 fungal species, 9 of them were of minimal spoilage effect on the unexposed cake samples while 14 were of higher spoilage effect on the exposed baked cake samples. It is recommended that; Proper preservatives and packaging materials should be used to avoid exposure of baked cake to fungi.
Table of contents
cover page 1
Title page 2
DECLARATION 3
CERTIFICATION 4
DEDICATION 5
ACKNOWLEDGEMENTS 6
ABSTRACT 8
CHAPTER ONE 13
INTRODUCTION 13
1.1 Background Of The Study 13
1.2 Statement of the Problem 16
1.3 Aim and Objectives of the Study 17
1.4 Purpose of the Study 18
1.5 Significance of the Study 18
1.6 Scope of the Study 18
1.7 Definition of Terms 19
LITERATURE REVIEW 22
2.1 Contamination of Baked Cake 22
2.2 Microbial Spoilage of Baked Cake 23
2.3 Physical Factors That Affect The Microbial Growth Of Fungi On Baked Cake 26
2.4 Control of Microbial Growth on Baked Cake 27
CHAPTER THREE 31
MATERIALS AND METHOD 31
3.1 MATERIALS 31
3.1.1 Description of Study Site 32
3.1.2 Sample Collection 32
3.2 Method 32
3.2.1Fungi Isolation and Identification 32
3.2.3 CHARACTERIZATION AND IDENTIFICATION OF FUNGI ISOLATES …………………………………………………..36
CHAPTER FOUR …………………………………………………………………………………………………………………………….………37
RESULTS AND DISCUSSION …………………………………………………………………………………………….……………….…41
4.0 RESULT ………………………………………………………………………………………………………………………………………..43
4.3 Discussion of Findings ……………………………………………………………………………………………………………….43
CHAPTER FIVE ……………………………………………………………………………………………………………………………………43
SUMMARY, CONCLUSION AND RECOMMENDATIONS ……………………………………………………………………….45
5.1 SUMMARY ………………………………………………………………………………………………………………………………..45
5.2 Conclusion ……………………………………………………………………………………………………………………………..…45
5.3 RECOMMENDATION …………………………………………………………………………………………………………………54
REFERENCES …………………………………………………………………………………………………………………………….45
CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
ungal contamination of baked cake and the possibility of fungal growth can pose a serious health problem when there are species which have the ability to synthesize and actively secrete toxic metabolites. It is known that aflatoxins produced by Aspergillus flavus and A. parasiticus, ochratoxin A. produced by Aspergillus ochraceus and some Penicillium spp., and some fusariotoxins produced by Fusarium spp., are strong cystotoxic and carcinogenic agents Annan-Prah et al., , (2011).
In most parts of Nigeria, people depend on snacks for a significant portion of their nutritional requirements. A snack is seen in western culture as a type of food not meant to be eaten as a main meal of the day like breakfast, lunch or dinner but rather to assuage a person’s hunger between meals, providing a brief supply of energy for the body. Snacks are ready to eat food, raw or cooked, hot or chilled but ready for immediate consumption at the point of sale without further treatment Chelea , Jideani (2006).
Generally, snacks are divided into continental and local Continental snacks include baked cakes sandwiches, kebabs, hotdogs, meat pie, salad, dough nuts, and other bakery products while local snacks include roasted corn, roasted plantain chips fried maize paste and so on Ogundare, Adetuyi (2003). Cake-making includes various ingredients such as cereal flour, cereals, cocoa, nuts, dried fruit, spices which regularly contain molds, these fungi on cakes can come from the air, contaminated packaging materials and other sources. When water activity is below 0.90 aw, mold appearance is a common type of microbial spoilage. Most molds are more resistant to drying, pH and osmotic pressure than bacteria and their presence always represents a potential risk of spoilage or diseases transmitted by fungi species . According to the available literatures, there are very few data on mold and mycotoxin contamination of baked cake. Given the importance of molds of fungi and their toxic metabolites in food products, the aim of this study was to determine the presence of potentially toxigenic species in different types of baked cake.
However , Microbial Standards of the Public Health Laboratories of the Advisory Committee for the Food and Dairy Products classify certain foods as unsatisfactory. This has to do with the microbial loads of such foods implying that they are not good for consumption. Foods that have fungal load greater than the standard threshold of 10-4 are considered unsafe. The baked cake sampled in this study though have some moulds that are not unsafe. The microbial load is quite below the threshold. However, there is need for more hygiene to be exercised while preparing these snacks so as to reduce the mould incidence. Permitted preservatives should be employed in the preparation of baked cake. Potassium sorbate is often used to prevent yeast and mould or fungi growth in baked foods like cake and other baked foods. This preservative loses effectiveness if the pH is greater than 6.5. Another factor that exposes snacks to mould infestation is the handling involved as it concerns the hawking mode of distribution. Hawkers should be made to observe some certain level of hygiene in their distribution process. They should observe the “best before dates” on product labels. The UK Food Standards Agency (IFA) has recalled expired cakes and confectionery Culliney, (2013).
In conclusion, it is important that all major players in the snacks industry should be aware of the risks posed by cake contamination as it relates to consumption of fungi toxins produced on contaminated baked cakes. Reports of loss of lives due to the activities of toxigenic fungus abound in the literatures and efforts should be made to reduce the risks. Therefore, there is need for systematic and universally applicable approach to food safety control.
1.2 Statement of the Problem
The major problems associated with baked caked is a frequent incidence of food contamination due to fungi and other related microorganisms which contribute to the contamination of the food substance. Earlier studies on the assessment of microbial contamination have reported poor knowledge practiced in food handling (FAO, 1995). Furthermore, like many other processed baked foods. Baked cake are subjected to physical, chemical and microbiological spoilage by fungi such as Rhizopus spp, Aspergillus spp and Penicillium spp Odu and Akano, (2012).
This study, would be able to faced devising methods and techniques to isolate and characterize the possible fungi that causes spoilage and extensive contamination of the baked caked. Due to the nature of these food processing and also the ingredients needed in preparing the baked cake, microorganisms e.g fungi is paramount in breeding microorganisms in baked cake.
Also, their methods of preparation involving extensive handling, is another problem to consider in the preparation process of cake. They are usually prone to contamination from water, air, storage/distribution facilities, environment and human activities (food handlers and vendors) Nelson (2006).
According to Coda, Cassone (2011), the major problem of long-term shelf life of baked cakes is contamination with fungi mostly of the genera Eurotium, Aspergillus, Monilia, Mucor, Cladosporium, Fusarium and Rhizopus. The implication of consuming contaminated bake cake is the risk associated with ingestion of mycotoxins and other allergens produced by these contaminants. The aim of this study is, therefore, to isolate and identify and characterize the various fungi associated with bake cakes sold in the Bori. This knowledge will inform on the possible mycotoxins that are by implication contained in such contaminated bake cakes and generally baked foods.
1.3 Aim and Objectives of the Study
The aim of this study is to isolate and characterize the fungi associated with baked cakes. The following are the basic objectives of the study;
- To determine the microbial content of baked unexposed and exposed cakes.
- To identify, isolate and characterize the fungi contained in baked cakes.
- To determine the appropriate methods and hygienic practice in the processing of baked cake.
1.4 Purpose of the Study
This study, is further designed to purposefully reduce the contamination of baked cake by fungi and other related microorganisms that contribute to the contamination of baked foods which can create high health challenges as a result of its consumption.
1.5 Significance of the Study
Many consumers and producers of the cakes need a precised and detailed knowledge on the process of baking cake and other valuable snacks. It is however, necessary for producers of cakes to follow the prescribed guidelines and health practices so as to reduce the level of contamination by fungi (fungus). And also it is necessary that bakers should use the right preservatives example potassium sorbate, to preserve growth.
1.6 Scope of the Study
This research study is designed to practically isolate and characterize the possible fungi that causes spoilage of baked cake. The baked cake are said to be contaminated when it is not processed and preserved hygienically by following the requirements and proportion of ingredients to be used during processing . Knowing that baked foods has high content of carbohydrates and other related sugar compounds that can facilitate the spoilage process by microorganisms. The study therefore spine around the ideas of checkmating the use of substandard materials in the baking process.
So far, it would also identify those highly characterized fungi that causes contamination of baked cake. Baked cake can be conveniently consumed without stress when there is no foul odour or taste based on the ingredients used. This indicates that, the study is to employ strategies that can produce good taste of baked cake and also reduce the contamination of the cake by fungi through appropriate preservative techniques.
1.7 Definition of Terms
The following key terms are operational in this research study
ASSOCIATED: It is defined as the act or style of being related or connected to another person. It can also be seen as a way of joining a group.
CHARACTERIZATION: In microbiology, characterization is the description of the distinctive nature or feature of microorganisms.
ISOLATION: In microbiology, isolation is the process of separating an organism from among others, i.e making a pure culture from a mixed culture.
CAKE: A cake form of sweet dessert that is typically baked in its oldest forms, cakes were modification of breads, but cakes now cove a wide range of preparations.
BAKING: This is process of cooking food by dry heat without direct exposure of a flame, typically in an oven.
FUNGI: Fungi are group living organism (microorganism) that are distantly related to plants and closely related to animals, but rather different from either of those groups they are saprophytic organism that grow on food e.g of fungi are yeasts, molds, rusts, smuts, mildews, and mushrooms etc.
MYCOTOXINS: A mycotoxin is a toxic secondary metabolite produced by organism of the fungus kingdom and is capable of causing disease and death in human and other animals.
ISOLATION: This is the process of separating setting apart or selecting from among other, so obtain pare or in free state. In microbiology, isolation is the process of separating culture form a mixed culture.
AFLATOXINS: Aflatoxins are poisonous carcinogens that are produced by certain molds which grow in soil, decaying vegetation, hay and grains they are usually found in improperly stood food e.g baked cake.
CARCINOGENIC: A carcinogen is a substances, radionuclide or radiations that promote carcinogenesis, the formation of cancer.
CYTOTOXIC: A Cytotoxic agent is any agent that can kill the cell.
OCHATOXINS: Ochratoxins are group of my cytotoxins produced by some aspergillums species and some Penicillium species
FUSARIOTOXINS: These are group of mycotoxins produced by species of the genus fusarium which occur once and toxicity varies considerably.
Pure culture: this is a culture containing a growth of a single kind of organisms free from other organism. It is a culture containing the descendants of a single organism whether free from all organisms of other kinds.
In microbiology a pure culture is a laboratory culture containing a single specie of organisms.
SERIAL DILUTION: This is the stepwise dilution of a substance in s solution
INOCULATION: This is the process of introducing an organism into a medium or prepared medium
INCUBATION: The provision of proper condition for growth and development.
INCUBATION period: the interval of time required for development or growth the act of maintaining controlled environmental conditions for the purpose of favouring growth or development of microbial or tissue cultures.
SUB- CULTURE: A sub-culture is a new cell or microbiological culture made by transferring some or all cells from a previous culture to a fresh medium. It is used to prolong the life and expand the number of cells of microorganisms in the culture.
Mix-Culture: A mix-culture is one which contains more than one organisms growing in a sterile medium.
CARCINOGENESIS: This is the formation of cancer where by normal cells are transformed into cancer cells. This is characterized by changes of the cellular, genetic and epigenetic levels.