Transcription
Food microbiology is a two-unit course, STM 324. This course is a prerequisite to industrial microbiology. That means that when you fail this course, you will not be able to register for your industrial microbiology and HND two first semester. I'm going to try my best to make it as simple and straightforward so that everyone will pass in flying colors.
The course has eight modules. The first module is we are going to be discussing sources of microbial contamination in foods. Sources of microbial contamination in food. How does our food get contaminated? What are the sources through which this food can be contaminated? We're going to be identifying some sources: air, water, soil, plants, humans, equipment, products, ingredients, you know, packaging materials. How do these sources become sources, I mean, become a point of contamination in food? That's going to be our first module.
Another first we'll do, we're going to see the role of soil microorganisms in agriculture. How do they improve soil fertility? How do they add to the soil in order to improve yield? We're also going to be looking at, um, water. What are those microorganisms that are in water that can be a source of contamination to food? And a major group will be discussed under these, and that's the group called the family Enterobacteriaceae. Their importance in water, and we're going to be discussing that also.
We're also going to explain how plants and animals could serve as a source of microbial contamination. I'm going to be explaining how humans can serve as sources of contamination, you know, equipment, food products, that's cross-contamination. There's going to be practical on this where you are going to be, um, exposed to some of these, um, some of these, um, tests. For example, for air, you want to confirm if organisms are in air, you're going to show you how, um, water can be a source of contamination to food in the laboratory. And we're also going to be screening water for coliform. That's the family Enterobacteriaceae. And I said earlier that yes, they are very significant in water quality control.
The second module, we'll be talking about factors that affect microbial growth in food. Now, organisms are in food, but there are some setting factors that will affect their growth. Other factors that are detrimental to them or factors that improve their growth in food. And before that, we're going to also be discussing the microbial growth of what happens in, in, um, in the growth curve. A microbial growth curve will only, um, take place. The four phases of microbial growth, which is the lag phase, the log phase, exponential phase, and the stationary phase, only upon in a closed system. And that's what we call a batch culture. But there's another type of culture that is called a continuous culture, and that will not go through the four phases. It either stops at the stationary phase or at the exponential phase, depending on your target metabolites.
Now, some factors affect the growth of microorganisms in food, and this can be divided into chemical factors, physical factors, and biotic factors. Other chemical factors, we have, um, things like nutrients, pH, redox potential, the presence of antimicrobial agents. We're going to be discussing how these factors affect the growth of microorganisms in food. Then under physical factors, we shall be discussing temperature, water activity, relative humidity, and biological structure. While the biotic factor has to deal with the growth rates, metabolism, and antagonism. These factors affect the growth of microorganisms in food, and we are going to deal with them extensively.
Module three will be discussing the techniques for the study of microorganisms. How do you study microorganisms in food? Okay, we now know that there are microorganisms in food because basically there's no food that is sterile. Now, how do you determine their presence in food? And that's what we mean by the technique for study of microorganisms. Here, we're going to be dealing with isolation, cultivation, um, isolation methods such as serial dilution, spread plate method, pour plate method, streaking. We're going to be discussing the colony-forming units. There's going to be a calculation under that. How do you determine your colony-forming units per sample? And under that is also going to be the practical section where serial dilution will be carried out, culturing will be done, isolation and identification of the isolates will also be done. And under that, we are going to be preparing pure cultures. You're going to carry out Gram staining, spore staining, capsule staining, and any other staining that is relevant.
Module four will be discussing microbiological study of specific foods. Microbiological study of specific foods. And that's a bit of a long module because under that we shall be discussing, um, non-useful functions of microorganisms in food. Non-useful functions, that means what do they do? They are, um, detrimental effect on food. And under that, we shall be discussing food spoilage and foodborne diseases. Food spoilage and foodborne diseases, that's the non-useful function of microorganisms in food.
Under that, we are also going to discuss useful functions of microorganisms in food. Useful functions of microorganisms in food. And there, we shall be discussing processing, preservation, you know, processing, preservation. And we're also going to be identifying microbial agents that are associated with the spoilage of different products: meat and meat products, poultry products, milk and dairy products, baked foods and confectionaries, fruits and vegetables, canned foods, dried foods, fish and seafood, cereal and cereal products. We're going to be discussing the microbial spoilage pattern, describing their storage conditions, as well as describe the useful functions of microorganisms in these products.
Module five has to do with microbial foodborne diseases. Microbial foodborne diseases. And under that, we shall be differentiating between food poisoning and food infection. Foodborne illness is caused by bacteria, parasites, viruses, protozoa. And the, the implication of these organisms in response to foodborne diseases. We're going to be discussing foodborne outbreak. What is an outbreak? How do these organisms get, um, how do they get established in the system of their hosts? You know, we're going to be discussing all that. There's also a practical on that. Are you going to isolate some culture organisms responsible for food poisoning? Food poisoning. And isolate spores from food. And actually screen them for the presence of some metabolites.
And the last module, which is module eight, we shall be discussing indices of food plant sanitation. Indices of food plant sanitation. Microbiological standards and criteria for setting up a food production premise. We want to set up a food production lab as a food microbiologist. What are the things that should be considered in building a food factory? Do you understand the design of the plants and, um, the sites? What are the things to consider? Ventures in the sites, the personnel, you know, all these shall be discussed. Then, um, going to be explaining the indices and criteria for examining microbial sanitation status of food production.
So, it's going to be an interesting class. Going to be an interesting class. I, I'll be taking this course with Mrs. Colady. This is Colady. I'm actually going to add her to the group so that, um, I'll be taking four modules and she'll be taking the other three modules. But let me just start with the introduction. As time goes on, you get to meet us. Now, for my class, what I do at the end of every module or every class, since it's online, you go to the classroom, which I believe that everyone has registered. You go to the classroom, Google Classroom, and answer a quiz. And that's what is going to be cumulative for my tests, for your test score. So make sure that I'm going to set the time. I'm sure you're familiar with that on how to do that. So at the end of every lecture, we shall have a short quiz.
So, the introduction of the course, food microbiology. You all know what microorganisms are. They are organisms that are too tiny to be seen with the naked eye. Our food is what we eat to give us energy. What we eat or drink in order to give us energy. Now, basically, the food that we eat, they are not sterile. There's nothing like sterile food, just like there's nothing like pure water. We'll just give it a name, pure, pure, pure. But in that water, we have, um, saprophytes, non-pathogens. Pathogens are disease-causing organisms. Non-pathogens, they are non-disease-causing microorganisms. Saprophytes are free-living, free-living organisms that do not cause disease. They derive nutrients from the food, you know, they derive nutrients from the food which they inhabit. But the major concern about food or water is for the pathogen. We don't want pathogens, disease-causing organisms, to be in the food.
So, basically, there are microbial associations whose composition depends upon which organism gains access and how they grow, survive, and interact in the food over time. So, just like in the animal kingdom, the survival of the fittest, it also happens within the food, um, environment. Organisms try to enter into the food, gain access into the food. While they do that, the food now serves as substrate for them, you know, substrate, and that they derive their own, um, nutrients from the food. And as they grow, they begin to spoil the food. How? By releasing metabolites into this food, metabolites, enzymes, chemical waste products, which now make the food to be spoiled.
Now, while the organisms are doing that, the food composition also has their own strategy. You know, they also have things within them that fight against these invading microorganisms in order for them not to be destroyed. This also happens in animals, human beings. For example, there's nothing like a sterile human being. In different parts of our body, we have microorganisms in them that are called the normal flora. If you like, use toothpaste from heaven to wash your mouth, you cannot remove the microorganisms that are in the mouth. They aid in digestion, and they also aid in keeping that environment the way it is. I'm not talking about people without other, that's another condition. Anyway, in our GIT, the gastrointestinal tract, we have, um, microorganisms that are normal flora in there, keeping the parts very healthy, except for the stomach because of the stomach acid. The acid in the stomach. But recently, we have discovered that even the stomach, an agent for, for ulcer, gastric ulcer. Now, on our skin, we also have microflora, normal flora on the skin. So, I'm just trying to tell you that just like plants are not sterile, they have their own inherent flora, microflora in them. So also animals, humans are not sterile.
Now, in most cases, the microflora in the food, they have no discernible effect, and the food is consumed without objection and with no adverse consequences. So, basically, when you want to eat, you don't need a microscope to, not look into your food to see whether, ah, let me use a microscope to check whether there's microorganisms in the food. No. Once the food is well cooked, you know, properly prepared, we just eat without objection and most times, no adverse consequence. But in some instances, microorganisms manifest their presence in several ways, and that's by causing, you know, they can cause food spoilage, they can cause foodborne illness, and they can transform, you know, they can even transform a food's property into a beneficial way. And that's why we talk about useful functions of microorganisms.
Now, one of the useful functions of microorganisms is when the food properties transform into a beneficial food fermentation. One of the useful functions of microbes is when you use the food as food supplements. Microorganisms as food supplements, um, mushroom, um, I've forgotten the name of this, um, single-cell proteins. Yeah, single-cell proteins. All these are foods produced by microorganisms that are useful. Foods are converted into beneficial cheese, yogurt. These are all products of fermentation. You know, most of our fermented food, all of the fermented food fall under this form of transformation. But the non-beneficial aspect of the food is when the food now becomes spoiled. It is a loss to you as a farmer, and it can also lead to foodborne illness when such foods are eaten. Those of you that like buying cheap products, you know, in the market, you know, broken tomato, they'll tell you, no problem, ah, just wash it and boil it and eat it. And sometimes you see already molds flying on these, um, items in the markets because they are cheap, we go for them. Well, you know, God has been faithful, and because some of us have a very strong immune system, now we don't come down with illness, and we just feel that, ah, there's no problem. The food, you are good to go.
Diversity of habitat. Viable microorganisms may be found in a very wide range of habitats. You find them everywhere. Hottest springs, these are the ones that are called the extreme thermophiles. The colders of brine ponds, extreme psychrophiles. You find them in wastes of polar regions, you know, and actively green bacteria occurs at temperatures in excess of over 100. Those are the extremophiles. The volcanic veins, the bottom of the oceans, you know, where boiling is prevented by the very high hydrostatic pressure. Occur in acidic waste, genius. They can occur in lake soda lakes. They can be isolated from black anaerobic suites of user and mold. All the purist waters or biologically unproductive or oligotrophic lakes.
Now, we are talking about their diversity. They can be found everywhere, everywhere. They are, they are going to call them cosmopolitans. Now, in all these and many other habitats, micro, they play an important part in recycling of organic and inorganic materials through their roles in the carbon, nitrogen, and sulfur cycles. I told you that in, um, in agriculture, they play a very important role. Of course, when there is no, uh, recycling or breaking down of all these, um, molecules or compounds into smaller useful ones that can be transformed into useful ones for plants as well as for animals, then how we are done for. Of course, when there is no microbial degradation, even the carcasses of humans and plants will be a problem. You know, there will be a great, so there will be a great problem of pollution for us. So, basically, they are found everywhere and they play an important role in the maintenance of stability of the biosphere.
The surfaces of plants, leaves, flowers, and the roots, as well as the guts of animals, have a rich microflora of bacteria, yeast, and filamentous fungi. I've mentioned that area. And one of other parts where you find these microorganisms is in the female genital tract, the vagina. You have the Lactobacillus there, and that's one of the reasons why women are advised not to use medicated soap to wash their private parts because when you do that, you displace the habitat, you kill the Lactobacillus, and the Lactobacillus, they're serving as a soldier, is a soldier guarding their parts, and you kill the soldier, you break the edge. Now, this happens to strike, and that's why yeast will proliferate, what you call Candida albicans. So, in my class, although this is food, but I'll try to use some medical terms to explain it. So please don't come and be laughing when we call the names the way it is, and don't claim to be too religious not to listen or or learn from what, uh, we shall be saying in the class.
Now, the natural normal flora may affect the original quality of the raw ingredients used in the manufacturing of the foods. You know, the normal flora can be a source of contamination to the food, and this may occur during processing. It can also occur when there is possibility of food spoilage or associated illness. Now, how does that happen? The, the, the parts, I mean, the organisms are actually normal. They are natural. They are part of the food. You want to ask fermentation. You know, when you make, for example, let me use a normal ogi as an example. You know, when you make your ogi, you grind your corn, you sieve it, and you have your pulp. What happens the following day? You know, the more the day of stay, the, the thicker, I mean, the more concentrated the satus, that's the acid that is produced. Have you ever thought of either where is the organism responsible for this fermentation coming from? It's coming from the plant product itself. So, these are natural. The organisms are natural in the, in the corn or the cereal, so they are the ones responsible for the fermentation. But because fermentation is a good process, now the organisms in fermentation, the lactic acid bacteria, the Lactobacillus.
So, now that we know that microorganisms can be found everywhere, let's take their habitat one by one. Microorganisms in the atmosphere. The atmosphere is one of the most hostile environments for microorganisms, but, um, in the suspended, there are tiny microbial propagules, and these propagules are subjected to desiccation, that's drying, and to the damaging effect of radial energy from the sun. They are also subjected to chemical activity of external elemental gaseous oxygen to which it will be intimately exposed. So many microorganisms, especially the Gram-negative, they die very rapidly when they are suspended in air. Although none is able to grow and multiply in the atmosphere at a significant, but a significant number of microbes are able to survive and they use the turbulence of the air as a means of dispersal. Why is it that the Gram-negative are the ones that will die rapidly? I, I want to believe that your understanding of bacteriology will tell you that the Gram-negative have a very thin, um, peptidoglycan layer in their cell wall, and last thing, peptidoglycan layer makes it easy for them, you know, to die off, and that makes it makes this very easy for them to be susceptible to most of these same environmental conditions, while the thick cell wall, in the thick peptidoglycan layer in the cell wall of the Gram-positive organisms, I mean, microbes and bacteria, makes them resistant to some of these factors.
So, how do you now determine their presence in air? There are methods of doing it: quantitative dissemination and qualitative determination. For the qualitative, you just want to know whether they are present or absent. For the quantitative, you want to know their exact number, the amount. So, for qualitative, which you are going to do in the lab, you just expose a petri dish that has an appropriate medium. It could be a general-purpose medium. There's nutrient agar. If you want to isolate bacteria, that's the general-purpose agar for isolation of bacteria. Or potato dextrose agar, if you want to isolate fungi. Or you can also use Sabouraud dextrose agar. Then you can also use, um, yeast extract agar for, um, isolation of yeast. That's also informed. Now, fungi have two major subgroups, which is yeast, which is the unicellular form of fungi, and the molds, which is the multicellular form of fungi. So, there are a few, um, bacteria genera that are present in air. And how does this air get contaminated? You know, they can be generated from aerosol from animal or human source or from water. You know, aerosols are those tiny droplets. For example, when you sneeze, you know, aerosols are released. And currently, as one of the means of contacting them, and covered. So, you are asked to sneeze into your elbow in order to reduce the dispersal of these aerosols. So, most times, when you use the toilet and you flush, you know, your water closet, you're supposed to cover your toilet seats, but some of us leave it open. Now, we stand there while we flush, but as you are doing that, aerosols are released, and you do not inhale it. It settles on the floor, settles on your hand, settles on your cloth, and you go straight to the kitchen. As a woman, and you go and start cooking. What do you think you are doing? Make your food. That's one thing I should have introduced in this course, that we should make our food our medicine and our medicine our food. And for the ladies, let your kitchen be your hospital for your family and not a graveyard.
So, examples of colonies that are found in air after these plates have been exposed and they are incubated at appropriate temperature, either for 24 hours or for 48 hours, you find the genus Micrococci, Corynebacterium, you find the Streptomycetes, that's the Actinomycetes family, you find Bacillus. These are because they are for Bacillus, there are spore formers. So their spores are actually present in these aerosols. So when they settle on a suitable medium, they grow, especially food. And they are, you know, dust. There's no way you can separate air from dust. So when those settles on your food. So for those of you that like buying food on the roadside, especially the ones displayed by the gutter, these foods are not covered. The flies will perch on the gutter and not perch on the food. Mama put food, akara, bread, etc. I'm not saying there's anything wrong with them. Look at the environments where this food is being prepared and the environment where these foods have been displayed. So that will tell you the quality of what you are eating. Therefore, the fungi group, you have, um, most of their conidia spores, they are also present in the air, you know. And when these bacteria, when these spores settle on food as a means of being dispersed by those particles, you know, through physical agitation, then they serve as a means of contamination in our food.
Microorganisms in the soil. I always said the soil is an environment that is extremely complex and has different, um, different soil have their own diverse flora of bacteria. No, different soil types have their own, um, diversity of flora: bacteria, fungi, protozoa, and algae. In our primary school teaching of soil, soil profile, you know, the topsoil, you have different types of microorganisms because it is top at the top and it's exposed to air. You have, for in microbiology, you find more of the aerobes, those organisms that will survive only in the presence of oxygen. So the deeper you go, the soil composition changes as well as the type of bacteria and fungi that will be present in that soil. For bacteria, you find more of the anaerobes because the deeper you go, the, um, the lesser the oxygen. So you have more of carbon dioxide that deep down in the soil. So you find more of the anaerobes under the, the, on the underground. Now, the soil is such a rich reservoir of microorganisms. It has provided many of the strains used for industrial production of antibiotics, enzymes, amino acids, vitamins, and other products that are used in both pharmaceutical and food industry. And one of that major group is the Actinomycetes. Those are the groups that are used for streptomycin, Streptomyces. So soil microorganisms participate in recycling of organic and nitrogenous compounds with an essential, which is essential if the soil is to support the active growth of plants. Ability to degrade complex organic material makes these, um, soil microorganisms potent spoilage organisms if they are present in food. You know, their natural habitat is the soil, but there's no way you can separate soil and food. You plant your crops, you harvest your crops, and most times when you have waste, there's no way you, you see fine soil. Even ordinary vegetables when you buy vegetables in the markets, and the best thing to do is to bring it home and wash the vegetables before you dice. But most of us ladies, because you are lazy, you ask the mama to cut it for you. So she will cut with the sand and everything. Now, the nutritionist will tell you the moment you break into the tissues of the vegetables, nutrients have been depleted. So some of us know how to wash our vegetables very well. You wash with salt or you wash with vinegar before you cook. Because most of these, so, but if when you wash properly, you'll find the bottom of your, or that's your container, sand. That's where the spores of most of these pathogens are. So when you cook your soup, the following day, when you come back to the kitchen to warm, you see bubbles inside your pot of soup, and when you taste it, it has gone sour. What happens? Despite the heat that was applied in the process of cooking, it's spore formers. So they have germinated and they have turned into vegetative cells the following day.
So, the common practice of protecting food from dust is justified in reducing the likelihood of inoculating the food with potential spoilage organisms. The soil is a very competitive environment and one in which the physical chemical parameters can change very rapidly. Yes, the parameters of the soil can change very rapidly. The kind of parameters you have during the dry season is different from the parameters you have during the rainy season. So in response to this, many soil bacteria and fungi produce resistant structures such as endospores of Bacillus and Clostridium, chlamydospores as clarity are of many fungi, which can withstand desiccation and a wide range of temperature fluctuations. So bacterial endospores are especially resistant to elevated temperatures. Their subsequent germination is frequently triggered by exposure to such temperatures, and their common occurrence in soil makes this important source of spoilage and food poisoning coming from Bacillus and Clostridium. We're going to treat that under foodborne diseases, food poisoning and food infection as a result of this same genus.
Microorganisms in water. We are still discussing the habitat. I just want to give us, um, a preview, you know, into the, the course before we go straight into sources of contamination. Want to know where they live before we now come to how they contaminate the, the food. Just a preview of where these microorganisms find themselves. So, in aquatic environments, it is an area and in area and in volume is the largest of the biosphere of both freshwater and the sea. And this contains many species of microorganisms adapted to these particular habitats. The sea around the coast are influenced by inputs of terrestrial and freshwater microorganisms and more importantly by human activity. You know, in Lagos, for example, the Lagos Lagoon, human activity. People are fishing in that lagoon. At the same time, people throw waste into the lagoon. Effluents are being discharged into the lagoon. Sewage, when they come to your house and clear your septic, they take it to that lagoon and empty it into the lagoon, thereby polluting the lagoon. Even though water has an ability of self-cleansing, but when the pollutant is even more than the activity of the water, they were in trouble. Now, this same water is where the fish in the fish is are harvested, and we buy and eat. Already the fish or the seafood have become contaminated. So let's go on. The sea has become a convenient dump for seaweed and other waste products. You know, even most of these production companies, they discharge their effluents into the sea. Although it is true that the sea has an enormous capacity to disperse such materials and render them harmless, okay, the scale of human activity has had a detrimental effect on coastal waters. You know, for example, the filtering feeding activity of shellfish. Now, shellfish, they feed by filtration, and this may lead to the entire recognition in infected person. Now, the fish is infected with enteric organisms. Enteric conditions that are coming from the sea, which, you know, of human physical effluents. Now, these things have been deposited into the water bodies, and thereby you not eat this shellfish, and the person can come down with either Salmonella, cholera, you know, um, um, E. coli infection. Freshwater may also act as a vehicle for bacterial producers or viruses, you know, causing disease through contamination of. I've mentioned that. Now, these organisms do not normally multiply in river and lake water. They may be present in low, but nonetheless significant numbers, you know, making it difficult for the presence of such organisms by actually actually looking for a special material that is present in large numbers. So now, when they appear in freshwater, because their presence is somehow, you know, disguised in freshwater, you may not see them in large numbers. So this freshwater, what we do in order to, um, establish their presence is to carry out what is called the, um, coliform test, and you look for what is called an indicator organism. An indicator organism. An indicator organism are organisms that are normally present in human or animal excreta. And a very good example of that is Escherichia coli. Now, Escherichia coli is used because it takes a long time for the organism to die when they are present in polluted water. And now, when you find, when you screen in the water, they are used as some water quality control, you know, test. When you find E. coli in your water, it signifies that other enteric organisms like Salmonella, Shigella, Vibrio cholera, Aeromonas will also be present in the water. So we use them as indicators. They are called a group of coliform, and under that, you have the total coliform and the fecal coliform. The fecal coliform is where E. coli belongs. And then Streptococcus, Enterococcus, Fecalis. These are the fecal coliforms.
Now, fungi are also present in both marine and freshwaters, but they do not have the same level of significance in food microbiology as other microorganisms. So they can produce very toxic metabolites which may become concentrated in shellfish without apparently causing, um, to them. But when the fish is consumed by humans, it can result in what is called paralytic shellfish poisoning. So we are still discussing habitats of microorganisms. We have discussed air, water, soil. Now I want to discuss humans or animals as a habitat for microorganisms. At the surfaces of humans and animals are exposed to soil and water, and there will always be the possibility of contamination of food and handling equipment and surfaces with these environmental microbes by direct contact with animal surfaces. Microorganisms are characteristic for each species of animal. And in humans, the normal skin flora is dominated by Gram-positive bacteria from the genera Staphylococcus. Now, Staphylococcus, bacterium, Propionibacterium. These are genera of, um, Gram-positive bacteria that have normal flora on our skin. And, you know, it baffles me when I hear all these people selling herbs for infertility, this stuff, look across our eyes, we kill you, this stuff. In fact, a little, you know, I just laugh. I'm not saying Staphylococcus are not, um, deadly, but there are some certain areas where when they find themselves in areas where it's not their natural habitat, they become pathogenic. Yes, but for the fact that people use that as a means of, you know, defrauding people, it baffles me. Anyway, it's going. So for animals that are killed for meat, their hide may be one of the most important sources of spoilage organisms. That's their skin. That's what we mean by hide. Now, the microbes in poultry, the microorganisms associated with feathers and the exposed follicles. Once the feathers are removed, may affect the microbial quality and potential shelf life of the carcass. So normally, they are present on the skin, but once you remove the skin, you have broken the edge. Human skin is the largest organ of the body, and their role is to protect, to defend. So they might, they start local causes on your skin. It's just they're doing their thing, enjoying itself, habitats, and nutrients. But the moment the skin is broken, they move from the skin into the deeper tissues, they become pathogenic. And that's where you get type, you know, those of you that like eating your nails with your teeth, you create an opening for staph, and they enter into it, and you know, they start eating into the tissues, and before you know it, post, before you know it, sleep last night.
So, the nose and the throat is also another habitat where you find these microorganisms. With the mucous membrane lining the nose and the, um, the throat, the mucous membrane is supposed to be a protective covering. And lying there, they have specialized, you know, they become a specialized environment, and these environments are colonized by a different group of microorganisms. They are usually harmless, but may have the potential to cause disease, especially following extreme temperature, starvation, when the person is unable to feed properly. And that's why they say it's not about eating, it's about eating balanced diets. So that balance will boost your immune system and to make your normal flora in that place to be active, to be able to convert any invading, um, microorganisms. They are outer soldiers defending our immune system. Overcrowding or other stress which lower the resistance of the host and make the spread of disease more likely in both human and other animals. What you do, I'm sure you've done, okay, that's in your HD2 immunology, you understand more of these how these factors affect overcrowding, starvation, stress, how these factors affect, you know, the immunity of the host. So, basically, in the human nose, you find more of the Staphylococcus aureus. The larger percentage of the human population carry this strain. And this strain, these aureus produce this species, sorry, produce a powerful toxin that is capable of eliciting a vomiting response. So now, they are found in the nose as normal flora. As children, we used to pick our nose and lick it. Those don't form any, um, big boy or big girl now. We all did it. Okay, you know, for the same staph, when they now find themselves in inhabited, aside the nose or the skin, they release toxins. And when they find themselves in food, they release toxins, and that leads to food poisoning.
So, what do you mean by food contamination? Is the state of being of food being impure or unfit for use. And when, um, there's an introduction of undesirable elements in the food, then that food becomes sort of contaminated. It can be contaminated by insects, rodents, chemicals, microbes, other foreign particles, and lots of, a lot, etc. No, the substances added may or may not cause problems. So that brings us to the three types of contamination: the physical contamination, chemical contaminants, and the biological or microbial contaminants. For physical contaminants, they are, they do not change or damage the food. You know, they are physical, you can see them, and you can actually sort them. They do not, they will not spoil food, but they can cause injury if the food is swallowed. And such food, such as the examples of such things are insect parts, rodent parts, or rodent excreta. When you find the excreta of rats in your gallery, you will remove it and you see it soak the gallery. But how will you remove the excreta of rats from your food? So broken parts of insects, the eggs of insects, you know, you find the larvae of insects, packaging materials. You find that some of these packaging materials are contaminated with different types of things. Sometimes when you check bottles, plastics, you find decks, you find different, uh, broken parts. Now, you can, this can be removed. So the two types of problems that arise from this is when large volume of that food is eaten, you know, or what they do, they destroy the food. The insects may destroy the food. When you have your, um, rice, your sorghum, or rice or beans, and weevils eat them up, they are destroying the food. The food is no longer useful for you. Weevils infest these, you show them, we so they cause waste. Then the microbes that may enter the food, like flies, you know, the airy feet of flies, they perch on, um, maybe septic or sewage that is now properly maintained. They now come up, perch on your food. The body of the insect carries, you know, what flies perch on our food or where rats, you know, eat part of our food, and it will climb on the food, and people still remove the parts that the rat have eaten. Um, what do you do? You mold, thereby very well, pour out soup into it, and you are good to go. You understand? So most of these insects may enter the food during production, during growth of the food, and you sometimes you find eggs of parasites of insects in wheat farm, you know, and during processing environments. That takes us to contaminants, I mean, chemical contaminants. While trying to keep insects and other pests under control, this can lead to chemical contamination. You know, the insecticides. There are chemicals that are used to improve the yield, you know, of food products of plants. So due to insect infestation, herbicides are also used to control weeds. But these pests, these pesticides or this herbicide now leave a residue in the food, and when these residues are eaten over time, they become a source of chemical contaminants in humans. And, you know, does it, it poses a major health hazard. We have had incidents of lead poisoning in water, you know, as a result of mining in the north, somewhere in Zamfara state. We've had issues of traders adding, um, sniper to beans so that their beans will not get infested with weevil. You know, but when these sniper-infested beans are eaten by humans, what happens? Food poisoning. Then the group of chemicals called the PCBs, they are among the most toxic substances, and this gets into water supplies. Chloroform, benzene, lead, you know, polychlorinated biphenyls. These contaminants get into our food, gets into our water, you know, when it rains, and these fields are actually being treated with pesticide. The rain water will actually be washed either into our wells, into our rivers, you know, into our bowls, and thereby coming back to us when we drink this water. Then the microbial contaminants, you know, as a result of microorganisms in the food. These microorganisms, they cause food spoilage, and when they are not properly taken care of, and this food is eaten by man, they can lead to foodborne diseases.