Introduction to food microbiology

1. Introduction to food microbiology A brief history Topics in food microbiology Survey of microbes

2. People have “practiced” food microbiology for thousands of years Even if they didn’t k know it

3. History of food microbiology • 8-10,000 years ago • Food preservation • Ca. 4,000 years ago • Fermented foods • 1600s • Early observations with microscopes • 1700s • Spontaneous generation was challenged (in experiments involving food)

4. 1800s –The Golden Age of Microbiology -Cell theory -Spontaneous generation disproved -Proof that fermentation is a biological process -Germ theory of disease -Canning invented -Discovery of organisms that cause foodborne illness -Techniques for studying microbes Koch’s postulateshttp://scienceblogs.com/digitalbio/wp-content/blogs.dir/460/files/2012/04/i-67928b6ba62e66dd3d1e18842c3e71d7-Kochs_postulates.gif

5. Sanitation More pathogens isolated from food, diseased animals, feces 1849 John Snow: cholera spread through water contaminated with feces Several waterborne pathogens isolated

6. Foodborne pathogens • Salmonella enteriditis- isolated from meat as well as person who ate it • Staphylococcus • Clostridium botulinum • Isolated in late 19th century • Koch’s postulates in action!

7. Techniques in microbiology • Pure culture technique • Microscopy • Staining, esp. Gram stain • Sterile microbiological media (liquid and solid) • Aseptic technique • Methods to control microbial growth • Biochemical tests to distinguish microbes • Studying beneficial microbes as well as pathogens

8. Molecular genetics and biotechnology • Rapid identification • Genetic engineering • Understanding mechanisms of resistance, biochemical processes, etc.

9. Limitations of microbiological techniques • Most microbes cannot be grown in the laboratory • Microbes do not grow in isolation • Most microbes have not even been discovered!

10. Topics in food microbiology • Fermentation/probiotics • Fermented foods and important metabolites • Making fermenting strains more stable • Resistant to viruses • Enhance fermentation capacity • Understanding probiotics and their effect on the body (the microbiome)

11. Food spoilage • Which microbes, and under what conditions? • What are the metabolites (products)? • How do they work in the cold? • How can they be controlled?

12. Foodborne pathogens • Detection • Identification • Control • How do we monitor and share information? • Are we making the problem worse? • Antibiotic resistance • Are we introducing pathogens through our processes?

13. What kinds of microbes are found in food? • Bacteria • Fungi (yeasts and molds) • Viruses • Protozoans, algae, helminths to a lesser extent • (Helminths=worms) • Protozoans and helminths are considered “accidental”

14. Classification of organisms emc.maricopa.edu Where are viruses and prions?

15. Prokaryotes vs eukaryotes prokaryotes eukaryotes Larger cells Cells have nucleus and organelles Can be single-celled or multicellular Plantae, Animalia, Fungi, Protista • Smaller cells • No nucleus or organelles • Single-celled • Bacteria and archaea • Viruses and prions are not cells so are not considered alive

16. Nomenclature • Binomial name: genus and species • Ex. Salmonella typhimurium; S. typhimurium • Subspecies: • Lactococcus lactis ssp. lactis, (soft cheese) • L. lactis ssp. cremoris (hard cheese) • Serovar, pathovar, biovar

17. Yeasts and molds • Yeasts: single-celled eukaryotes • Molds: multicellular structure (filaments, spores) required for reproductions • Can be used to make foods but also involved in spoilage • Saccharomyces cerevisiae: • Carbon dioxide and ethanol

19. Molds can grow almost anywhere • Food spoilage • Toxins • Allergens • Food processing • Different genera grow on different foods • Rhizopus- fruits, vegetables, bread • Geotrichum- dairy mold • Penicillium-spoils almost everything, but also used to make cheese

20. Viruses infect cells Can cause disease Interfere with food processing T4-infects E. coli Hepatitis A- infects humans

21. Protozoans, algae, helminths • Protozoans can cause parasitic disease (Giardia, Cryptosporidium, Toxoplasma) • Algae- photosynthetic protists • Contaminants, food products, toxins • Helminths- parasites • Roundworms, tapeworms- contaminated food

22. Life cycle of a tapeworm (helminth) humanillnesses.com

23. Bacteria (“eubacteria”) • We will spend much lecture time, and most lab time, working with them • Classification is complicated and changing all the time • Most bacterial species have not been described, but many have been very well studied

24. Major classification criteria morningsidemicro.wikidot.com Gram-positive or Gram-negative

25. Morphology Scienceblogs.com www.zazzle.com

26. Bacterial classification, continued • Aerobes, anaerobes, fermenters • Spore formers, non spore formers • What metabolic products do they produce? • Acids, alcohols, gases- and which ones? • What do they use for food? • Carbohydrates, lipids, proteins • Under what conditions do they grow? • Temperature range, pH range, availability of water Do they cause disease? What kind?

27. What should a food microbiologist know? • Characteristics of the different types of microbes • How to identify and enumerate them • Factors that affect their growth (innate and introduced) • Fermentation vs spoilage • How microbes cause disease • That the field of food microbiology is a work in progress!