1. LECTURE PRESENTATIONS For BROCK BIOLOGY OF MICROORGANISMS, THIRTEENTH EDITION Michael T. Madigan, John M. Martinko, David A. Stahl, David P. Clark Lectures by John Zamora Middle Tennessee State University © 2012 Pearson Education, Inc. Food Preservation and Foodborne Microbial Diseases Chapter 36

2. 36.1 Microbial Growth and Food Spoilage 36.2 Food Preservation 36.3 Fermented Foods and Mushrooms I. Food Preservation and Microbial Growth © 2012 Pearson Education, Inc.

3. 36.1 Microbial Growth and Food Spoilage Food spoilage –Any change in appearance, smell, or taste of a food product that makes it unpalatable to the consumer –Food may still be safe to eat, but is regarded as unacceptable The chemical composition of a food determines its susceptibility to microbial spoilage –Perishable –Semiperishable –Nonperishable © 2012 Pearson Education, Inc.

4. 36.1 Microbial Growth and Food Spoilage Susceptibility to food spoilage is based in large part on moisture content –Perishable foods have higher moisture content than nonperishable foods Fresh foods are spoiled by both bacteria and fungi –Spoilage organisms are those that can gain access to the food and use the available nutrients For example, Escherichia coli frequently contaminates meat products because it is found in animals’ digestive tracts © 2012 Pearson Education, Inc.

5. 36.1 Microbial Growth and Food Spoilage Growth of Microorganisms in Foods –Microbial growth follows the normal pattern for bacterial growth –Only during the last few population doublings is food spoilage actually observed © 2012 Pearson Education, Inc.

6. 36.2 Food Preservation Methods for slowing spoilage and foodborne disease –Cold –Pickling and acidity –Drying and dehydration –Heating –Aseptic food processing –Chemical preservation –Irradiation © 2012 Pearson Education, Inc.

7. 36.2 Food Preservation Cold –Slows microbial growth rate and delays spoilage –Psychrotolerant bacteria can grow at refrigerator temperatures –Freezing allows for longer storage, but isn’t suitable for all foods © 2012 Pearson Education, Inc.

8. 36.2 Food Preservation Pickling and acidity –pH is an important factor in microbial growth –Most foods are neutral or acidic –At pH <5, most spoilage organisms are inhibited –During pickling process, acetic acid is added to a solution with sugar or salt Pickled foods include pickles, fish, peppers, and fruits © 2012 Pearson Education, Inc.

9. 36.2 Food Preservation Drying and dehydration –Moisture content (water activity) is critical for microbial metabolic processes –Sugar and salt reduce the availability of water for microbial growth (in effect, dehydrating it) Examples: jams, jellies, meats, fish –Lyophilization (freeze-drying) is the physical removal of frozen water under vacuum Very expensive, but very effective © 2012 Pearson Education, Inc.

10. 36.2 Food Preservation Heating –Used to reduce the bacterial load (i.e., pasteurization) of a product or to actually sterilize it (i.e., canning) –Canning isn’t always 100% effective (Figure 36.2) Failure results in swollen cans (DO NOT EAT!) © 2012 Pearson Education, Inc.

11. Figure 36.2 © 2012 Pearson Education, Inc.

12. 36.2 Food Preservation Aseptic food processing –Several foods are now processed and packaged aseptically –This food can be stored on shelves for months or longer –Involves flash heating and packing in sterile containers –Examples: juice boxes and milk substitutes © 2012 Pearson Education, Inc.

13. 36.2 Food Preservation Chemical preservation –Over 3,000 compounds are used as food additives –A small number of these are used to control microbial growth Examples: sodium propionate, sodium benzoate, nitrites Some, such as nitrates, are controversial because studies show they may be harmful to human health –Significantly extends shelf life of finished foods © 2012 Pearson Education, Inc.

14. 36.2 Food Preservation High-pressure processing (HPP; Figure 36.3) –High hydrostatic pressure to kill pathogens and spoilage organisms –Works on fruits, vegetables, ready-to-eat meats, and juices © 2012 Pearson Education, Inc.

15. Figure 36.3 Piston under pressure Water Packaged food Pressure- resistant vessel © 2012 Pearson Education, Inc.

16. 36.2 Food Preservation Irradiation –Food is irradiated with ionizing radiation to reduce bacterial, fungal, and insect contamination –Uses gamma or beta radiation, or X-rays –Irradiated foods must be labeled (Figure 36.4) © 2012 Pearson Education, Inc.

17. Figure 36.4 © 2012 Pearson Education, Inc.

18. 36.3 Fermented Foods and Mushrooms Many common foods are preserved, produced, or enhanced by the actions of microbes –Fermentation is the anaerobic catabolism of organic compounds (generally carbohydrates) –Important bacteria in the fermented food industry are lactic acid bacteria, propionic acid bacteria, and acetic acid bacteria –Products of fermentation include yeast bread, cheese, yogurt, buttermilk, sausage, sauerkraut, and soy sauce (Figure 36.5) © 2012 Pearson Education, Inc.

19. Figure 36.5 © 2012 Pearson Education, Inc.

20. 36.3 Fermented Foods and Mushrooms Dairy Products –Include cheese, yogurt, buttermilk, and sour cream –Lactic acid bacteria are added to the milk and the fermentation proceeds for a certain time period –Some products require a second fermentation © 2012 Pearson Education, Inc.

21. 36.3 Fermented Foods and Mushrooms Meat Products –Sausages are made from pork, beef, and poultry Blend of meat, salt, and seasonings Lactic acid bacteria are added to the mixture After fermentation, sausages are smoked and dried –Fish, often mixed with rice, shrimp, and spices © 2012 Pearson Education, Inc.

22. 36.3 Fermented Foods and Mushrooms Vegetables and Vegetable Products –Sauerkraut (fermented cabbage) –Pickles (fermented cucumbers) –Olives, onions, tomatoes, peppers, and many fruits are also fermented –Vegetables are often fermented in salt solutions © 2012 Pearson Education, Inc.

23. 36.3 Fermented Foods and Mushrooms Soy sauce (Figure 36.6) –Complex fermentation product of soybeans and wheat –Fermentation for 2 to 4 months in large vats Vinegar –Conversion of ethyl alcohol to acetic acid (Figure 36.7) –Acetic acid bacteria include Acetobacter and Gluconobacter –Processes for production: open vat (Orleans) method, trickle (quick vinegar) method, and bubble method © 2012 Pearson Education, Inc.

24. Figure 36.6 © 2012 Pearson Education, Inc.

25. Figure 36.7 Cytochrome o Proton motive force Alcohol dehydrogenase Aldehyde dehydrogenase Acetaldehyde EthanolAcetic acid © 2012 Pearson Education, Inc.

26. 36.3 Fermented Foods and Mushrooms Mushrooms (Figure 36.9) –Commercially grown mushroom is the basidiomycete Agaricus bisporus Generally cultivated in “mushroom farms” –Another widely cultured mushroom is the shiitake, Lentinus edulus © 2012 Pearson Education, Inc.

27. Figure 36.9 © 2012 Pearson Education, Inc.

28. II. Foodborne Disease, Microbial Sampling, and Epidemiology 36.4 Foodborne Diseases and Microbial Sampling 36.5 Foodborne Disease Epidemiology © 2012 Pearson Education, Inc.

29. 36.4 Foodborne Diseases and Microbial Sampling Food poisoning (also called food intoxication) –Disease that results from ingestion of foods containing preformed microbial toxins –The microorganisms that produced the toxins do not have to grow in the host Food infection –Microbial infection resulting from the ingestion of pathogen-contaminated food followed by growth of pathogen in the host © 2012 Pearson Education, Inc.

30. 36.4 Foodborne Diseases and Microbial Sampling Microbial Sampling for Foodborne Disease –In addition to nonpathogenic microorganisms, pathogenic microorganisms may be present in fresh foods Rapid detection methods have been developed to look for the presence of some of these pathogens (e.g., E. coli O157:H7) Tests are molecular and immunology based In the U.S., foodborne outbreaks are reported to the CDC © 2012 Pearson Education, Inc.

31. 36.5 Foodborne Disease Epidemiology Clusters of cases caused by microorganisms in a single source of food Widespread multiple disease outbreaks caused by processing plant or food distribution center Spinach and Escherichia coli (0157:H7) –E. coli (0157:H7) well studied (Figure 36.11) and quickly traced © 2012 Pearson Education, Inc.

32. Figure 36.11 © 2012 Pearson Education, Inc.

33. III. Food Poisoning 36.6 Staphylococcal Food Poisoning 36.7 Clostridial Food Poisoning © 2012 Pearson Education, Inc.

34. 36.6 Staphylococcal Food Poisoning Food poisoning is often caused by toxins produced by Staphylococcus aureus (Figure 36.12) –S. aureus can grow on common foods, and some strains produce heat-stable enterotoxins –Gastroenteritis occurs within a few hours of consumption It is estimated that 185,000 cases of staphylococcal food poisoning occur each year Enterotoxins of S. aureus classified as superantigens produce large T cell response and an inflammatory response © 2012 Pearson Education, Inc.

35. Figure 36.12 © 2012 Pearson Education, Inc.

36. 36.7 Clostridial Food Poisoning Clostridium perfringens (Figure 36.13) and Clostridium botulinum cause serious food poisoning –Produce endospores that may not be killed during cooking/ canning process C. perfringens is the most commonly reported form of food poisoning, with 248,000 annual cases –Large numbers of cells (>10 8 ) must be ingested –Enterotoxin is produced in the intestinal tract 6–15 hours after consumption © 2012 Pearson Education, Inc.

37. Figure 36.13 © 2012 Pearson Education, Inc.

38. 36.7 Clostridial Food Poisoning Botulism is a severe and often fatal food poisoning –Caused by an exotoxin produced by Clostridium botulinum –Botulinum toxin is a neurotoxin, but is destroyed by heat –Average of 24 cases annually (Figure 36.14) –16% of cases are fatal –Home-prepared foods are a common source of illness © 2012 Pearson Education, Inc.

39. Figure 36.14 Infant botulism Foodborne botulism Outbreaks caused by fermented fish/seafood products, Alaska Outbreak caused by baked potatoes, Texas Outbreak caused by chili sauce, Texas Year Cases 201020052000199519901985 100 90 80 70 60 50 40 30 20 10 © 2012 Pearson Education, Inc.

40. IV. Food Infection 36.8 Salmonellosis 36.9 Pathogenic Escherichia coli 36.10 Campylobacter 36.11 Listeriosis 36.12 Other Foodborne Infectious Diseases © 2012 Pearson Education, Inc.

41. 36.8 Salmonellosis Salmonellosis is a gastrointestinal illness caused by foodborne Salmonella infection –40,000–45,000 documented cases per year (Figure 36.15) –Chickens and pigs may harbor Salmonella –Onset of the disease occurs 8–48 hours after ingestion –Disease normally resolves in 2–5 days Salmonella ingested in food or water invades phagocytes and grows as an intracellular pathogen © 2012 Pearson Education, Inc.

42. Figure 36.15 72 64 56 48 40 32 24 16 8 0 Year Cases (in thousands) 197519801985199019952000 20052010 © 2012 Pearson Education, Inc.

43. 36.9 Pathogenic Escherichia coli Most E. coli are nonpathogenic All pathogenic strains are intestinal parasites, and a few produce potent enterotoxins –Shiga toxin–producing E. coli (STEC), formerly called enterohemorrhagic E. coli (EHEC, i.e., O157:H7), produce verotoxin –Verotoxin causes bloody diarrhea and kidney failure Other types of E. coli are enterotoxigenic (ETEC), enteroinvasive (EIEC), and enteropathogenic (EPEC) © 2012 Pearson Education, Inc.

44. 36.10 Campylobacter Campylobacter spp. (Figure 36.16) –Common cause of bacterial foodborne infections in the United States –More than 2,000,000 cases of bacterial diarrhea per year –Transmitted to humans via contaminated food Poultry, pork, raw shellfish, or in surface waters Campylobacter replicates in the small intestine Cause high fever, headache, malaise, nausea, abdominal cramps, and bloody stools © 2012 Pearson Education, Inc.

45. Figure 36.16 © 2012 Pearson Education, Inc.

46. 36.11 Listeriosis Listeria monocytogenes (Figure 36.17) is the cause for listeriosis –May lead to bacteremia and meningitis –No food product is safe from contamination –Psychrotolerant L. monocytogenes is an intracellular pathogen –Uptake of the pathogen by phagocytes results in the growth and proliferation of the bacterium Mortality rate of listeriosis is 20% © 2012 Pearson Education, Inc.

47. Figure 36.17 © 2012 Pearson Education, Inc.

48. 36.12 Other Foodborne Infectious Diseases Other Bacteria –Yersinia enterocolitica causes foodborne infections due to contaminated meats and dairy products Can lead to life-threatening enteric fever –Bacillus cereus grows in food that is cooked and left to cool slowly Causes diarrhea and vomiting –Shigella spp. cause nearly 100,000 cases of severe foodborne invasive gastroenteritis each year © 2012 Pearson Education, Inc.

49. 36.12 Other Foodborne Infectious Diseases Viruses –The largest number of annual foodborne infections are thought to be caused by viruses Noroviruses (Figure 36.18) are responsible for most infections 9,000,000 annual cases of foodborne disease © 2012 Pearson Education, Inc.

50. Figure 36.18 © 2012 Pearson Education, Inc.

51. 36.12 Other Foodborne Infectious Diseases Protists –Important foodborne diseases are caused by Giardia intestinalis, Cryptosporidium parvum, and Cyclospora cayetanensis (Figure 36.19) –Can be spread in foods contaminated by fecal matter in water used to wash, irrigate, or spray crops –Fresh fruits are often the source of these infections –Toxoplasma gondii can be spread by raw or undercooked meat © 2012 Pearson Education, Inc.

52. Figure 36.19 © 2012 Pearson Education, Inc.

53. 36.12 Other Foodborne Infectious Diseases Prions –Proteins that adopt novel conformations that inhibit normal protein function and cause degeneration of neural tissue (Figure 36.20) –“New variant Creutzfeldt–Jakob Disease” Linked to bovine spongiform encephalopathy (BSE), a prion disease –180,000 European cattle have been diagnosed with BSE © 2012 Pearson Education, Inc.

54. Figure 36.20 © 2012 Pearson Education, Inc.