Isolation And Identification Of Moulds On Baked Food (Bread And Cake)

Project and Seminar Material for Science Laboratory Technology SLT

Isolation And Identification Of Moulds On Baked Food (Bread And Cake)


The isolation and identification of moulds in baked food (Bread and Cake) was carried out in the laboratory. The infestation of mould on bread depends on the kind and number of the agent present and upon the environment about them. This statement makes it clear that microorganism infest foods having suitable environment condition for their microbial activity. This project work is centered on knowing the fungal micro-organisms that infests bread which emails the isolation and identification of the moulds, the source of contamination a known standardized system called hazard analysis critical control point which ensures hygienically produced breads.

This study was aimed at identifying the fungi associated with the spoilage of commercial bread in Enugu state, Nigeria with a view of creating more awareness on the dangers posed by the consumption of such fungal infested product. The fungi were isolated using the spread plate technique withsabouraud dextrose agar as the growth medium. The percentage moisture content as well as the PH of the samples were also determined. The fungal counts ranged between 1.2 x 103 cfu/ml and 4.3 x 103 cfu/ml. Chichi had the highest fungal count of 4.3 x 103 cfu/ml while Yale bread had the lowest count of 1.2 x 103 cfu/ml. The fungi were characterized and identified on the basis of their macroscopic and microscopic characteristics as Aspergillus spp, Rhizopusspp, Penicilliumspp, Cladosporiumspp and Mucor spp. Aspergillus spp occurred most frequently while Cladosporiumspp had the lowest frequency of occurrence in the bread and cake samples.

The percentage moisture content ranges between 43.2 and 43.7, with Chichi bread having the highest percentage moisture content of 43.7 while Yale bread had the lowest percentage moisture content of 43.2. The PH of the samples ranged between 4.90 and 4.98. Chichi bread had the highest PH value of 4.90 while Yale bread had the lowest PH value of 4.98. The fungi isolated in this study are known to cause diseases of humans through their production of toxins. Their presence in significant number in bread is a public health risk, therefore adequate hygiene must be maintained during the baking, handling, storage and marketing of the product to minimize the entry and proliferation of the these organisms. The incorporation of food grade chemical preservatives is also recommended.

Table of contents

Preliminary Page(s)

  • Title page
  • Certification page
  • Dedication
  • Acknowledgement
  • Abstract
  • Table of content

Chapter One:


  • 1.1 Background of the study
  • 1.2 Statement of problem
  • 1.3 Aims and objectives of the study
  • 1.4 Hypothesis
  • 1.5 Significance of study
  • 1.6 Scope of the study
  • 1.7 Limitation of the study

Chapter Two:

Literature Review

  • 2.1 Introduction
  • 2.2 Formulation and bread making
  • 2.3 Flour
  • 2.4 Economical importance of bakery products
  • 2.5 Microbial spoilage of bakery products
  • 2.5.1 Bacterial spoilage
  • 2.5.2 Yeast spoilage
  • 2.5.3 Mold spoilage
  • 2.6 Physical factors influence the microbial growth activity
  • 2.6.1 Effect of temperature, pH and water
  • 2.6.2 Effect of salt tolerance
  • 2.7 Control of microbial growth in bakery products
  • 2.7.1 Reformulation to reduce product aw
  • 2.7.2 Freezing
  • 2.7.3 Preservatives
  • 2.8 Effect of chemical preservatives
  • 2.8.1 Sorbic acid and sorbates
  • 2.8.2 Propionic acids and its salts
  • 2.9 Effect of biopreservatives

Chapter Three:

Material And Methods

  • 3.1 Sample Collection and Processing
  • 3.2 Mould isolation
  • 3.3 Characterization and Identification of the Isolates
  • 3.4 Determination of the Moisture Content of the Bread and cake samples
  • 3.5 Determination of the pH of the Bread and cake samples
  • 3.6 Data Analysis

Chapter Four:

Results And Discussion

  • 4.1 Results
  • 4.2 Discussion

Chapter Five:

Conclusion And Recommendation

  • 5.1 Conclusion
  • 5.2 Recommendations
  • References

Chapter One


1.1 Background of the study

Food spoilage by mould is a natural problem occurring more or less frequently depending on the nature of food and the environmental conditions, in addition to the economic consequences of mould growth. Some fungal species have been proven to produce mycotoxins in food, which may constitute a potential health hazard for the consumer (Alan, 1999).

Baked food such as bread, cake are the most staple food in the world. These food are spoiled by moulds especially Penicillin species, Aspegillus species. However, the dominant spoilage mould depends on the type of bread and the storage temperature. Mycotoxigenicmould can be isolated from spoilage breads, and many mycotoxins have been produced in inoculated breads, but survey of naturally moulds breads have yielded afflotoxin and Ochrotoixn A in few samples of baked food (Kroll, 1993). Mould growth in baked food bread and cake can be reduced by a range of techniques which includes: proper hygienic within the bakery to reduce the opportunities for mould spores to gain access to the product, pasteurization of bread once packaged, use of preservatives which reduces or prevent the growth of moulds (Samuel, 2000).Food can be contaminated with spoilage on pathogenic organisms ( micro). Infestation of these moulds spoil the product so that it is not fit to eat; it also changes the taste so that the product is not desirable.

The concept of food infestation of moulds is based on the consipteration for fiutres of consumption. Infestation is defined as the over presence alone has led to its growth and microbial activity. Pathogenic organisms however can cause food poisoning. Food poisoning can arise through infatuation of food by organisms (micro) which secrete toxins which B their consumed. The cost of fungal infested bread resulting to spoilage is also great with loss of money due to wastage of the raw materials. Also considering the usefulness of this product in the community with the management of money being spent it has also helped in the sense that since it is regarded as a fast food it is being bought and consumed directly without further preparations done. Effect of contaminated bread in the society can lead to an epidemic of gastrointestinal disorder where by that particular environment that consumed the contaminate bread become affected there by developing stomach upset. As a result of this a lot of consideration should be given to breads that are sent into the community to be sold and this is done by the standardized system called HACCP ie hazards Analysis critical control point.

This method is now generally considered as a choice for ensuring safety of foods (jay 1996 de Boer and Beumer 1999) hazzard analysis critical control point involves identifying places in the production process where hazzard could occur. i.e. the CCp (critical control point” and putting monitoring procedures in place to prevent these hazards occurring even with this system in place samples still need to be tested for the presence of microorganism.
Detection of most of the microorganisms requires growth of the organism on selective media which can take a number of days from isolation to identification.

These method are sensitive and gives qualitative information on the number and nature of the microorganism. Present in a food sample. However, conventional methods require several day to produce result because they rely on the ability of microorganisms to multiply to visible colonies (De Boser and Beumer 1999). Presentation of bread commonly involves the use of propionates and sorbates and sometime henzoates. Preservatives are added to retain on to increase the shelf life by preventing the micro-organism responsible for the contamination of that food. There alter natives to preservatives have been bought also. The chief types of microbial spoilage of bread as a result of fungal infestation will also studied which is moldiness. Rapines is also another type of bread spoilage but unfortunately it wont be studied due to the fact that it is caused by bacterial organism which unfortunately is not a fugal organism and as a result is not in the scope of study for this research work. Also a spoilage not so common called CHALKY BREAD caused by a yeast like Fungi, will be diseased.

Bread is one of the important staple foods in most countries. It is prepared by baking dough primarily composed of flour and water. The combinations of different flours and ingredients such as salts, fats, yeasts, eggs, sugars, spices, fruits, vegetables, nuts and seeds have resulted in the wide variety of types, sizes and textures. Bread is an important source of carbohydrates, proteins, lipids, vitamins, fibers and minerals.

Bread may be served in different forms at any meal of the day, eaten as a snack and is even used as an ingredient in other culinary preparations. As a basic food worldwide, bread has become significant in religious rituals, secular cultural life and languages. Bread is prone to spoilage problems. These include physical, chemical and microbial spoilage. Mould growth is the major economic importance of bread and is a serious and costly problem for bakeries and consumers. The moulds involved in the spoilage of bread include Rhizopussp, Penicilliumsp, Eurotiumsp, Aspergillus sp and Moniliasitophila. One of the most common is Rhizopusstolonifer, often referred to as the bread mould.

Economic losses of bread due to mould spoilage are between 1% and 5% depending on the type of product, season and the method of processing. In addition to the economic losses associated with bread, another concern is the possibility of mycotoxins production by some moulds. The concentration of nutrients also determines the rate of mould growth in bread. The growth of mould in bread is a substrate-saprophyte relationship with the bread providing nourishment and the mould surviving on it as long as favourable environmental conditions prevail.
Mould growth in bread is also favoured by their ability to synthesize proteolytic and amylolytic enzymes. Furthermore, moisture condensation on a bread surface due to packaging while the product is not completely cool, may be conducive to mould growth.

The aim of this study was to isolate, characterize and identify the filamentous fungi associated with the spoilage of commercial bread in Enugu, Nigeria so as to educate the consuming public on the danger inherent in the consumption of such spoilt bakery product.

1.2 Statement of problem

A major causes of growth of mould in baked food (Bread and cake) is long storage. Baked product being food consumed, entails large purchase from bakery, and at times the sellers do not finish the sale within a week. These long storage causes growth of mould, resulting to food poisoning as a result of the toxins produce by these mould infected bread.

Research conducted shows that people especially in rural areas consume mould infected bread and also the prevalence of food borne disease is high in these area. Problems encountered by the society as a result of the consumption of contaminated bread infested with mould art circulation in the market places are related health wise, in the sense that when contaminated. Breads are eaten; it leads to caster or intestinal disorder by some mould which is a result of deposited toxins. This can lead to an epidemic, when a batch of count ammoniated breading in circulation.

Problems due to spoilage yeasts in bread usually result from post-baking contamination. Yeast spoilage is characterized by visible growth on the surface of bread. Wild yeast such as Trichosporon, Saccharomyces spp, Pichia and Zygosaccharomyces can also cause spoilage of bread. Saccharomyces spp produce white spots in bread leading to the term Chalk bread. Yeasts that cause problem in bread can be divided into the wild yeast which grows on the surface of the bread in white and pinkish patches and fermentative yeast which are associated with alcoholic and essence odours. Yeasts are however not more common in bread than filamentous fungi.

1.3 Aims and objectives of the study

This project is based on the isolation and identification of moulds on baked food (bread and cake). To examine the species of mould that infest bread at room temperature.

Given below are the specific objectives of the study

  1. To identify the mould responsible for spoilage in baked food (Bread and cake)
  2. To isolate moulds in the product (Bread and cake).
  3. To know the effect of the mould implicated in bakery foods (Bread and cake).

1.4 Hypothesis

H0 – filamentous fungi and yeast has no effect on bread .

H1 – filamentous fungi and yeast are responsible for spoilage of bread when infested.

1.5 Significance of study

The isolation and identification of mould in baked product would provide a knowledge of the effect of mould on the baked product, these would thereby improve the needs to preserve baked foods (Bread and cake), and reduce the rate of food poisoning from consumer’s of the product.

The justification of this research study is to ensure that a well prepared baked bread devoid of fungal growth is being circulated on sold. It is also carried out on the basic of selling well baked breads uncontaminated so as to avoid any don’t of food poisoning associated with the ingestion of bread.

1.6 Scope of the study

This study focused on bakeries in Enugu. This project work is limited to the isolation and identification of moulds on baked food (bread and cake). This is also limited restricted on the examination of the end product which is the baked bread and not its raw material which is the flour, practical works is carried out on the pathogenically of species identified as this could be another area of study for interested microbiologists.

1.7 Limitation of study

Lack of finance limited the scope of the project work, as it interfered in the sourcing for information, and also it affected the practical work as there was not enough money to purchase some laboratory materials that are non-existence.

Chapter Five

Conclusion And Recommendation

5.1 Conclusion

Baked products are prone to mould spoilage. The knowledge of the filamentous fungal spoilage of bread will educate the consumers on the public health implications of the growth of the organisms and their toxins in bread and proffer the possible solutions to such spoilage. Spoilage of bread by filamentous fungi is a costly problem for bakeries and the use of safe food grade chemical preservatives and maintenance of aseptic conditions in baking and post-baking processes are therefore means of minimizing bread spoilage.

The study shows that the predominant efficacy of preservatives in bakery foods. Mold spoilage is still a major problem limiting the shelf life of many high and intemediate moisture bakery products. Losses due to mold spoilage have been resulting in lost revenue to the baking industries.

In conclusion, it is important that all major players in the snacks industry should be aware of the risks posed by baked products contamination as it relates to consumption of mould toxins produced on contaminated snacks. Reports of loss of lives due to the activities of toxigenic moulds abound in literature and efforts should be made to reduce the risks. Therefore, there is need for systematic and universally applicable approach to food safety control

5.2 Recommendations

Methods to control mold growth and to extend the shelf life of bakery products is of great economic importance to the baking industry where an increased demand in global consumption exists. Therefore, the study recommended that measures as good hygiene in the bakeries and if necessary complementary post packaging heat treatments or modified atmosphere packaging is the best alternatives. Adequate hygiene must be maintained during the baking, handling, storage and marketing of the product to minimize the entry and proliferation of the organisms. The incorporation of food grade chemical preservatives is also recommended.

Isolation And Identification Of Moulds On Baked Food (Bread And Cake)

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