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Food microbiology 3

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This document provides information on food spoilage and food poisoning. It defines food spoilage as any changes that make food unacceptable for consumption. The major causes of spoilage are microorganisms, enzymes, insects/rodents, chemical reactions, environmental factors, and time. There are three types of microorganisms that cause spoilage: yeasts, molds, and bacteria. Eating spoiled food can cause food poisoning, with symptoms like nausea. Food poisoning is classified as foodborne infections or intoxications. Foodborne infections involve live bacteria growing in the body, while intoxications involve toxins produced by bacteria. Methods to prevent spoilage include temperature control, removing water/air, altering pH, using food additives, and

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College of Health Sciences Dep. of Medical Laboratories Food Microbiology Theory 3rd stage Lecture 3 Dr.: Shameeran S. Ismael BVM & S, M.Sc Medical Microbiology(Parasitology), PhD Molecular Parasitology

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Food spoilage Food spoilage can be defined as: • Any changes in the visual, smell and texture of food that makes it unacceptable for consumption. • Or is the process in which food deteriorates to the points it is not edible to humans or its quality of edibility becomes reduced.

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• The major causes of food spoilage include: 1. Microorganisms, their growth and activity 2. Action of enzymes 3. Insects, rodent and parasites 4. Chemical reactions of the constituents of food 5. Environmental factors such as temp., moisture, air and light 6. Time

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Food microbiology 3

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1. Activity of Microorganism • Microorganisms capable of spoiling food are available commonly in soil, water and air, on the skin of cattle, fruits and vegetables, on the feathers of poultry, on the hulls of grains, and shells of nuts, on the clothing and skin of handling personnel, on processing equipment and within the intestines and body cavities of animal and human body

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There are three types of microorganisms that cause food spoilage a. Yeasts growth • Yeast growth causes fermentation which is the result of yeast metabolism. There are two types of yeasts true yeast and false yeast. • True yeast metabolizes sugar producing alcohol and carbon dioxide gas. This is known as fermentation. • False yeast grows as a dry film on a food surface, such as on pickle brine. False yeast occurs in foods that have a high sugar or high acid environment.

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b. Moulds grow in filaments forming a strong mass which is visible as `mould growth'. Moulds form spores which, when dry, float through the air to find suitable conditions where they can start the growth cycle again. • Mould can cause illness, especially if the person is allergic to molds. The main symptoms from eating mouldy food will be nausea or vomiting from the bad taste and smell of the mouldy food.

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• Both yeasts and moulds can thrive in high acid foods like fruit, tomatoes, jams, jellies and pickles. Both are easily destroyed by heat. Processing high acid foods at a temperature of 100°C in a boiling water canner for the appropriate length of time destroys yeasts and moulds.

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c. Bacteria may grow under a wide variety of conditions. There are many types of bacteria that cause spoilage. They can be divided into: spore- forming and nonspore-forming bcteria.

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• Bacteria generally prefer low acid foods like vegetables and meat. In order to destroy bacteria spores in a relatively short period of time, low acid foods must be processed for the appropriate length of time at 116°C in a pressure canner. (Temperatures higher than 100°C can be obtained only by pressure canning.)

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2. Action of Native Enzymes • The activity of endogenous enzymes in plant and animal foods is often intensified after harvest/slaughter due to lack of control mechanisms in the harvested plant food/ slaughtered animal • The native enzyme may be inactivated by heat, radiation/by the use of specific chemicals.

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Examples: • Browning Enzymes again cause browning in certain foods the moment they are exposed to air. When you cut or bruise food such as apple or yam, the exposed surface will discolor and turn brownish due to the activity of enzymes.

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• Ripening Enzymes are involved in the process that causes ripening in certain foods such as fruits and vegetables. Unripe bananas for example contain starch which is gradually converted to sugars, until the banana becomes very sweet, and its skin color changes from green to yellow. Eventually, the skin color changes to dark brown and it is no longer fit to be consumed.

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3. Insects, Parasites and Rodent: • Insects destroy cereal grains, fruits and vegetables by not only consuming the food but contaminating the food, Facilitate microbial attack on foods • Parasites enter the human body mostly through poultry which have been improperly cooked • Rodent apart from consuming considerable quantity of food also contaminate the food through their droppings, urine and filth. Rodents are also carries of pathogenic bacteria

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4. Chemical Reaction • The quality of foods damage due to chemical reactions of the constituents of food. • Ex: the unsaturated fatty acid components undergo oxidation due to exposure to atmospheric air giving rise to oxidative rancidity in fat rich foods • Free fatty acids may also be released due to hydrolytic reactions causing odor as well as undesirable changes in the texture of food • Losses of vitamins due to oxidation or light induced reactions also occur

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5. Environmental Factors • Air and oxygen can have detrimental effects on vitamin A, C, food color, flavour and other constituents • Oxidation reaction are facilitated due to the present of air • Light destroy riboflavin, vitamin A, Vitamin C and also promotes light induced oxidation reactions affecting flavour and color of food. Light also causes destruction of protein as in the case of milk

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6. Time • The quality of food remains at its peak for some time soon after its harvest/slaughter and thereafter as time progress, the deterioration in the quality of the food also progress. • Simple option for maintaining the food quality, through temporarily • We should keep the food alive as long as possible. This option is however, limited in its application

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• The harvested / slaughtered food must be cleaned and cooled immediately. This delays the onset of deterioration of food quality but does not prevent it.

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Food microbiology 3

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What happens when you eat spoiled food? • Eating spoiled food caused by bacteria can cause food poison. • Food poisoning occurs when you swallow food or water that has been contaminated with certain types of bacteria, parasites, viruses, or toxins. • Most cases of food poisoning are due to common bacteria such as Staphylococcus, Escherichia coli (E. coli), clostridium botulinum and salmonella

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Food poisoning or food borne illness Food poisoning is Illness caused by the infection with microorganisms and ingestion of toxins produced, and chemical poisoning. Causes: • Bacteria and their toxins • Viruses • Chemicals • Vegetable poisoning

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• Foods contaminated with pathogenic microorganisms usually do not look bad, taste bad, or smell bad. It is impossible to determine whether a food is contaminated with pathogenic microorganisms without microbiological testing.

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Classification of food borne diseases • Food borne diseases are classified into: 1. Food borne infections 2. Food borne intoxications

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1.Foodborne infection  Is caused by the ingestion of food containing live bacteria which grow and establish themselves in the human intestinal tract. These can either be bacterial, viral, Parasitic.  Food borne infections tend to have long incubation periods and are usually characterized by fever.

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Bacterial food borne infections • Bacteria are the most troublesome and important biological foodborne hazard for the foodservice and food retail Establishment. Bacterial cells can exist in two different states: - the vegetative state and the spore state. • Spores are produced when the bacterial cell is in an environment where it cannot grow (frozen foods, dried foods) • Ex:Escherichia coli, Salmonella spp., Shigella spp., Campylobacter jejuni,Listeria monocytogenes, Vibrio spp

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Viral food-borne infections • Food-borne viruses differ from food-borne bacteria. They are the smallest and simplest form of life known. Unlike bacteria, they do not reproduce or grow in foods. They are usually transferred from one food to another, from a food handler to a food, or from a water supply to a food. • Ex: Hepatitis A,

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Food-borne Parasites • Parasitic infection is far less common than bacterial or viral food-borne illness. There are many examples of parasites that can enter the food system and cause food-borne illness. • Like: Entamoebae histolytica, Giardia lamblia, Toxoplasma gondii, Trichinella spiralis

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2.Food borne intoxication • Food borne intoxication is caused by ingesting food containing toxins formed by bacteria which resulted from the bacterial growth in the food item. The live microorganism does not have to be consumed. • Food borne intoxications have short incubation periods (minutes to hours) and are characterized by lack of fever. Food borne intoxications can be classified into: a. Bacterial intoxications b. Fungal intoxications c. Chemical intoxication d. Plant toxicants e. Poisonous animals

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• Bacterial food borne intoxication, there are some bacteria including: Staphylococcus aureus, Bacillus cereus, Clostridium perfringens and Clostridium botulinum

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• Fungal intoxications: These are caused by consumption of metabolites produced by fungi, when growing in food. These metabolites are called mycotoxins. Grains, oilseeds, fruits and vegetables are mostly involved if they are stored at high humidity or if they are not properly dried before storage. • Aflatoxicosis is caused by aflatoxins produced by the fungi, e.g. Aspergillus flavus. There are four types of aflatoxins have been described i.e. aflatoxin B1 , B2 , G1 and G2 . Animals consuming feeds contaminated with aflatoxin B1 leads to secretion in the milk of aflatoxin M1 and M2

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Reasons for keeping foods from spoilage • Deterioration may cause food to be wasted • Contaminated food can cause illness and in severe cases cause food poisoning • Money is saved when food commodities are kept from spoilage • When food is kept from spoilage, it maintains it nutritive value

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How to prevent food spoilage? Food Preservation: Temperature treatments Removal of water Removal of air Alteration of pH

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Food additives Food Additives , natural and synthetic compounds added to food to supply nutrients, to enhance color, flavor, or texture, and to prevent or delay spoilage. Some additives can inactivates or kill micro- organisms, retard chemical spoilage

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• Preservative food additives can be antimicrobial; which inhibit the growth of bacteria or fungi, including mold, or antioxidant; such as oxygen absorbers, which inhibit the oxidation of food constituents. Common antimicrobial preservatives include calcium propionate, sodium nitrate, sodium nitrite, sulfites (sulfur dioxide, sodium bisulfite, potassium hydrogen sulfite, etc.)and disodium EDTA.

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• Colorings - To offset color loss and to produce a consistently colored food product Additives can cause allergic reactions in some people. Colorings, in particular are thought to cause hyperactivity or asthmatic symptoms especially in children and young people.

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Thanks for attention,, Please check UOD Moodle and Google classroom

More Related Content

Food microbiology 3

  • 1. College of Health Sciences Dep. of Medical Laboratories Food Microbiology Theory 3rd stage Lecture 3 Dr.: Shameeran S. Ismael BVM & S, M.Sc Medical Microbiology(Parasitology), PhD Molecular Parasitology
  • 2. Food spoilage Food spoilage can be defined as: • Any changes in the visual, smell and texture of food that makes it unacceptable for consumption. • Or is the process in which food deteriorates to the points it is not edible to humans or its quality of edibility becomes reduced.
  • 3. • The major causes of food spoilage include: 1. Microorganisms, their growth and activity 2. Action of enzymes 3. Insects, rodent and parasites 4. Chemical reactions of the constituents of food 5. Environmental factors such as temp., moisture, air and light 6. Time
  • 5. 1. Activity of Microorganism • Microorganisms capable of spoiling food are available commonly in soil, water and air, on the skin of cattle, fruits and vegetables, on the feathers of poultry, on the hulls of grains, and shells of nuts, on the clothing and skin of handling personnel, on processing equipment and within the intestines and body cavities of animal and human body
  • 6. There are three types of microorganisms that cause food spoilage a. Yeasts growth • Yeast growth causes fermentation which is the result of yeast metabolism. There are two types of yeasts true yeast and false yeast. • True yeast metabolizes sugar producing alcohol and carbon dioxide gas. This is known as fermentation. • False yeast grows as a dry film on a food surface, such as on pickle brine. False yeast occurs in foods that have a high sugar or high acid environment.
  • 7. b. Moulds grow in filaments forming a strong mass which is visible as `mould growth'. Moulds form spores which, when dry, float through the air to find suitable conditions where they can start the growth cycle again. • Mould can cause illness, especially if the person is allergic to molds. The main symptoms from eating mouldy food will be nausea or vomiting from the bad taste and smell of the mouldy food.
  • 8. • Both yeasts and moulds can thrive in high acid foods like fruit, tomatoes, jams, jellies and pickles. Both are easily destroyed by heat. Processing high acid foods at a temperature of 100°C in a boiling water canner for the appropriate length of time destroys yeasts and moulds.
  • 9. c. Bacteria may grow under a wide variety of conditions. There are many types of bacteria that cause spoilage. They can be divided into: spore- forming and nonspore-forming bcteria.
  • 10. • Bacteria generally prefer low acid foods like vegetables and meat. In order to destroy bacteria spores in a relatively short period of time, low acid foods must be processed for the appropriate length of time at 116°C in a pressure canner. (Temperatures higher than 100°C can be obtained only by pressure canning.)
  • 11. 2. Action of Native Enzymes • The activity of endogenous enzymes in plant and animal foods is often intensified after harvest/slaughter due to lack of control mechanisms in the harvested plant food/ slaughtered animal • The native enzyme may be inactivated by heat, radiation/by the use of specific chemicals.
  • 12. Examples: • Browning Enzymes again cause browning in certain foods the moment they are exposed to air. When you cut or bruise food such as apple or yam, the exposed surface will discolor and turn brownish due to the activity of enzymes.
  • 13. • Ripening Enzymes are involved in the process that causes ripening in certain foods such as fruits and vegetables. Unripe bananas for example contain starch which is gradually converted to sugars, until the banana becomes very sweet, and its skin color changes from green to yellow. Eventually, the skin color changes to dark brown and it is no longer fit to be consumed.
  • 14. 3. Insects, Parasites and Rodent: • Insects destroy cereal grains, fruits and vegetables by not only consuming the food but contaminating the food, Facilitate microbial attack on foods • Parasites enter the human body mostly through poultry which have been improperly cooked • Rodent apart from consuming considerable quantity of food also contaminate the food through their droppings, urine and filth. Rodents are also carries of pathogenic bacteria
  • 15. 4. Chemical Reaction • The quality of foods damage due to chemical reactions of the constituents of food. • Ex: the unsaturated fatty acid components undergo oxidation due to exposure to atmospheric air giving rise to oxidative rancidity in fat rich foods • Free fatty acids may also be released due to hydrolytic reactions causing odor as well as undesirable changes in the texture of food • Losses of vitamins due to oxidation or light induced reactions also occur
  • 16. 5. Environmental Factors • Air and oxygen can have detrimental effects on vitamin A, C, food color, flavour and other constituents • Oxidation reaction are facilitated due to the present of air • Light destroy riboflavin, vitamin A, Vitamin C and also promotes light induced oxidation reactions affecting flavour and color of food. Light also causes destruction of protein as in the case of milk
  • 17. 6. Time • The quality of food remains at its peak for some time soon after its harvest/slaughter and thereafter as time progress, the deterioration in the quality of the food also progress. • Simple option for maintaining the food quality, through temporarily • We should keep the food alive as long as possible. This option is however, limited in its application
  • 18. • The harvested / slaughtered food must be cleaned and cooled immediately. This delays the onset of deterioration of food quality but does not prevent it.
  • 20. What happens when you eat spoiled food? • Eating spoiled food caused by bacteria can cause food poison. • Food poisoning occurs when you swallow food or water that has been contaminated with certain types of bacteria, parasites, viruses, or toxins. • Most cases of food poisoning are due to common bacteria such as Staphylococcus, Escherichia coli (E. coli), clostridium botulinum and salmonella
  • 21. Food poisoning or food borne illness Food poisoning is Illness caused by the infection with microorganisms and ingestion of toxins produced, and chemical poisoning. Causes: • Bacteria and their toxins • Viruses • Chemicals • Vegetable poisoning
  • 22. • Foods contaminated with pathogenic microorganisms usually do not look bad, taste bad, or smell bad. It is impossible to determine whether a food is contaminated with pathogenic microorganisms without microbiological testing.
  • 23. Classification of food borne diseases • Food borne diseases are classified into: 1. Food borne infections 2. Food borne intoxications
  • 24. 1.Foodborne infection  Is caused by the ingestion of food containing live bacteria which grow and establish themselves in the human intestinal tract. These can either be bacterial, viral, Parasitic.  Food borne infections tend to have long incubation periods and are usually characterized by fever.
  • 25. Bacterial food borne infections • Bacteria are the most troublesome and important biological foodborne hazard for the foodservice and food retail Establishment. Bacterial cells can exist in two different states: - the vegetative state and the spore state. • Spores are produced when the bacterial cell is in an environment where it cannot grow (frozen foods, dried foods) • Ex:Escherichia coli, Salmonella spp., Shigella spp., Campylobacter jejuni,Listeria monocytogenes, Vibrio spp
  • 26. Viral food-borne infections • Food-borne viruses differ from food-borne bacteria. They are the smallest and simplest form of life known. Unlike bacteria, they do not reproduce or grow in foods. They are usually transferred from one food to another, from a food handler to a food, or from a water supply to a food. • Ex: Hepatitis A,
  • 27. Food-borne Parasites • Parasitic infection is far less common than bacterial or viral food-borne illness. There are many examples of parasites that can enter the food system and cause food-borne illness. • Like: Entamoebae histolytica, Giardia lamblia, Toxoplasma gondii, Trichinella spiralis
  • 28. 2.Food borne intoxication • Food borne intoxication is caused by ingesting food containing toxins formed by bacteria which resulted from the bacterial growth in the food item. The live microorganism does not have to be consumed. • Food borne intoxications have short incubation periods (minutes to hours) and are characterized by lack of fever. Food borne intoxications can be classified into: a. Bacterial intoxications b. Fungal intoxications c. Chemical intoxication d. Plant toxicants e. Poisonous animals
  • 29. • Bacterial food borne intoxication, there are some bacteria including: Staphylococcus aureus, Bacillus cereus, Clostridium perfringens and Clostridium botulinum
  • 30. • Fungal intoxications: These are caused by consumption of metabolites produced by fungi, when growing in food. These metabolites are called mycotoxins. Grains, oilseeds, fruits and vegetables are mostly involved if they are stored at high humidity or if they are not properly dried before storage. • Aflatoxicosis is caused by aflatoxins produced by the fungi, e.g. Aspergillus flavus. There are four types of aflatoxins have been described i.e. aflatoxin B1 , B2 , G1 and G2 . Animals consuming feeds contaminated with aflatoxin B1 leads to secretion in the milk of aflatoxin M1 and M2
  • 31. Reasons for keeping foods from spoilage • Deterioration may cause food to be wasted • Contaminated food can cause illness and in severe cases cause food poisoning • Money is saved when food commodities are kept from spoilage • When food is kept from spoilage, it maintains it nutritive value
  • 32. How to prevent food spoilage? Food Preservation: Temperature treatments Removal of water Removal of air Alteration of pH
  • 33. Food additives Food Additives , natural and synthetic compounds added to food to supply nutrients, to enhance color, flavor, or texture, and to prevent or delay spoilage. Some additives can inactivates or kill micro- organisms, retard chemical spoilage
  • 34. • Preservative food additives can be antimicrobial; which inhibit the growth of bacteria or fungi, including mold, or antioxidant; such as oxygen absorbers, which inhibit the oxidation of food constituents. Common antimicrobial preservatives include calcium propionate, sodium nitrate, sodium nitrite, sulfites (sulfur dioxide, sodium bisulfite, potassium hydrogen sulfite, etc.)and disodium EDTA.
  • 35. • Colorings - To offset color loss and to produce a consistently colored food product Additives can cause allergic reactions in some people. Colorings, in particular are thought to cause hyperactivity or asthmatic symptoms especially in children and young people.
  • 36. Thanks for attention,, Please check UOD Moodle and Google classroom