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INTRODUCTION TO FOOD MICROBIOLOGY PEOPLE HAVE “PRACTICED” FOOD MICROBIOLOGY FOR THOUSANDS OF YEARS Even if they didn’t k know it HISTORY OF FOOD MICROBIOLOGY • 8-10,000 years ago – • Ca. 4,000 years ago – • Fermented foods 1600s – • Food preservation Early observations with microscopes 1700s – Spontaneous generation was challenged (in experiments involving food) 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/wpcontent/blogs.dir/460/files/2012/04/i-67928b6ba62e66dd3d1e18842c3e71d7Kochs_postulates.gif SANITATION 1849 John Snow: cholera spread through water contaminated with feces Several waterborne pathogens isolated More pathogens isolated from food, diseased animals, feces 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! 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 MOLECULAR GENETICS AND BIOTECHNOLOGY Rapid identification Genetic engineering Understanding mechanisms of resistance, biochemical processes, etc. 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! 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) 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? 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? 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” PROKARYOTES • • • • Smaller cells No nucleus or organelles Single-celled Bacteria and archaea EUKARYOTES • Larger cells Cells have nucleus and organelles Can be single-celled or multicellular Plantae, Animalia, Fungi, Protista Viruses and prions are not cells so are not considered alive PROKARYOTES VS EUKARYOTES 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 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 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 VIRUSES INFECT CELLS Can cause disease Interfere with food processing T4-infects E. coli Hepatitis A- infects humans PROTOZOANS, ALGAE, HELMINTHS Protozoans can cause parasitic disease (Giardia, Cryptosporidium, Toxoplasma) Algae- photosynthetic protists Contaminants, food products, toxins Helminths- parasites Roundworms, tapeworms- contaminated food 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 MAJOR CLASSIFICATION CRITERIA Gram-positive or Gram-negative morningsidemicro.wikidot.com Morphology www.zazzle.com Scienceblogs.com BACTERIAL CLASSIFICATION, CONTINUED Aerobes, anaerobes, fermenters Spore formers, non spore formers What metabolic products do they produce? What do they use for food? Acids, alcohols, gases- and which ones? Carbohydrates, lipids, proteins Under what conditions do they grow? Temperature range, pH range, availability of water Do they cause disease? What kind? 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!
