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  • Building World Class Microbiological Food Safety Systems for the Coming Storm

    Back to The Basics: Factors Influencing the Growth,

    Survival and Death of Microorganisms

    By: Jeffrey L. Kornacki, Ph.D.

    President and Senior Technical Director Kornacki Microbiology Solutions, Inc. Adjunct Assistant Professor, Food Science Department, UGA

    Palm Spings, CA

    March 20, 2017

    No Electronic copies please

  • Our lives are inextricably woven with the lives of these creatures who we ignore until they cause us trouble

    Lynn Margulis and

    Dorion Sagin Microcosmos, 1986

    Kornacki Microbiology Solutions, Inc.

    Thar she blows! Dead whale explodes Taiwanese street, shops showered after gases built up inside

    Taiwan Apple Daily via Reuters Blood and guts litter this street in Tainan, Taiwan, after decomposing organs in the sperm whale in background caused it to explode. 11:48 ET Jan 29th, 2004

    MSNBC staff and news service reports

    No Electronic copies please

  • General Principles of Food Microbiology: Groups of Significance to Foods

    Five groups significant in foods Bacteria: e. g. Mycobacterium bovis-

    tuberculosis, milk early 1900s USA Fungi: yeasts, molds (e.g. Candida ? Aspergillus flavus) Rickettsia: e.g. C. burnetti, Q fever - milk Parasites: Cryptosporidium (300,000, 1993,

    MKE, WI) Viruses: Hepatitis A, Noravirus, Noravirus-


    No Electronic copies please

  • General Principles of Food Microbiology: Microbes and Size Multiply in foods: Only Bacteria, fungi (focus) Entailments: spoilage, growth increases risk from

    weaker pathogens and others, enrichment techniques can be done

    Others: Not multiply in foods e. g. Rickettsia, parasites (viruses) Entailments: Enrichments cannot be done Require a concentration and/or amplification

    (PCR) step

  • Relative Size Relationships of Microorganisms

    Micron (m) 1/1,000,000 meter

    Basketball (228,600 um; 9 inches)

    Yeast (5m)

    Large Marble (25,000 m; 1 in)

    Listeria (0.5m)

    Head of Pin (1500 m; 0.06 in)

    Virus 10-100 nm

    Grape fruit (137,000 m; 5.4 in)

    Mold spore (3m)

    Kornacki, J. L. 2010. What Factors Are Required for Microbes to Grow, Survive and Die? Chapter 5. In, Principles of Microbiological Troubleshooting in the Industrial Food Processing Environment. Springer NY. Pp. 103-115.

  • Listeria monocytogenes Growing on Stainless Steel 800X (Grooves)

    Image taken with an epiflourescent microscope of DNA stained biofilm Courtesy of Emeritus Professor Joseph Frank, University of Georgia

  • Types of Microbes - Shape

    Cocci: Staphylococcus aureus, Streptococcus pyrogenes

    Rods: Bacillus cereus, Clostridium

    perfringens, Listeria (short), Escherichia coli (short), Salmonella

    Spiral: Campylobacter jejuni

  • Types of Microbes Cell Wall

    Gram positive: Staphylococcus aureus Streptococcus pyrogenes Gram negative: E. coli, Salmonella Acid fast: Mycobacterium spp.

  • Cell Walls and Staining

  • Selected Gram Stain Reactions of Bacteria

    Description English: microscopic image of a Gram stain of mixed Gram-positive cocci (Staphylococcus aureus ATCC 25923, purple) and Gram-negative bacilli (Escherichia coli ATCC 11775, red). Magnification:1,000.

    Date 13 April 2010(2010-04-13) Source Y tambe's file Author Y tambe

    Other versions

    File:Staphylococcus_aureus_Gram.jpg, File:Escherichia_coli_Gram.jpg : microscopic image of a Gram stain of each bacteria

  • Spore Stain

  • Microbial Identifications Gram stain > 23 theoretical possibilities Gram positive or negative Rod or coccus shaped (or spiral) Spore or non-spore former Catalase (positive or negative) Oxidase (positive or negative) >25 possibilities: enough to get to Family and often

    Genus level Other simple tests: gas, CHO fermentations

  • Since the days of cave man, the earth has never been a garden of Eden, but a Valley of Decision where resilience is essential to survivalTo grow in the midst of dangers

    is the fate of the human race.

    Rene Dubos Mirage of Health

    And of bacteria (JLK)

  • Approximate Temperature Ranges of Growth for Selected Microbial Categories

    ----------------------------------------------------------------------------------- Temperature (0C) ------------------------------------------------------- Minimum Optimum Maximum

    ----------------------------------------------------------------------------------Psychrophilic -15-0 10-20 20-22

    Psychrotrophic --5-5 25-30 30-40 Mesophilic 5-25 25-40 40-50 Thermophilic 35-45 45-65 60-90 Obligate 40-45 55-65 70-90 Facultative 35-40 45-55 60-80

  • Types of Microbes Growth Temperature Relationships Psychrophiles NA Psychrotrophic Listeria monocytogenes,

    Yersinia enterocolitica Selected strains of Cronobacter (E.

    sakazakii1) Entailments: refrigerated growth refrigerated foods cold environments

    cold enrichment Mesophilic Salmonella Thermophilic B. coagulans, C. thermosaccharolyticum 1Gurtler, J. B., J. L. Kornacki, and L. R. Beuchat. 2005. Enterobacter sakazakii: A coliform of increased concern to infant health. Int. J. Food Microbiol. 104:1-34.

  • Characterization Based Upon Optimum Growth Temperature

  • Minimum Growth Temperatures of Selected Microorganisms*

    Microorganism Temperature oC Aeromonas 5oC Clostridium Genera include pyschrotrophs

    C. botulinum 3.3 10oC Enterobacter Genera include pyschrotrophs Escherichia coli 5-10oC Lactobacillus 2oC Leuconostoc 4oC Listeria 1oC Pseudomonas fluorescens 0-4oC Salmonella 3-10oC

    *Adapted from Kornacki, J. L. and D. A. Gabis. 1990. Microorganisms and refrigeration temperature. Dairy, Food and Environmental Sanitation 10 (4):192-195.

  • Minimum Growth Temperatures of Selected Microorganisms (continued.)*

    Staphylococcus 5-10oC

    Yersinia enterocolitica 4oC

    Candida (Yeast) 0oC

    Saccharomyces 0-7oC

    Aspergillus Genera include psychrotrophs

    Penicillium Genera include psychrotrophs

    *Adapted from Kornacki, J. L. and D. A. Gabis. 1990. Microorganisms and refrigeration temperature. Dairy, Food and Environmental Sanitation 10 (4):192-195. (now called Food Protection Trends)

  • Selective Properties of Foods Intrinsic vs. Extrinsic Intrinsic properties (water activity, pH, Eh) Extrinsic - temperature (cooking, smoking),

    drying, irradiation, high pressure, etc.)

  • Intrinsic Properties of Foods Influencing Microbes Intrinsic Factors1 Water activity (aw): Formulation salt in the moisture phase, dissolved solutes Dry vs. wet heat resistance 71.7oC 15 seconds: fluid milk 7-9

    log10 cfu decline Salmonella 71.7oC milk chocolate: many hours for 1D- value (one study; 70oC, 12-17.5 hours) 1Goepfert, J. M., I. K. Iskander, and C. H. Amundson. 1970. Relation of the heat resistance of salmonellae to the water activity of the environment. Appl. Microbiol. 19(3):429-433. 2Mitscherlich, E. and E. H. Marth. 1984. Microbial Survival in the Environment. Springer-Verlag, New York. Table 6, Page 584.

  • Limiting aw's of Selected Microbes Compared to Typical Food aw's aw Selected Food Microbe 0.98-1.00 Fresh Fish/Poultry

    0.97 C. bot. type E 0.96 Some Ripened

    Cheeses E. coli

    0.95-1.00 Fresh Meats 0.93-0.96 Salmonella

    0.92-0.95 B. cereus

    0.90-0.98 C. botulinum 0.92 Listeria 0.90-0.94 Lactobacillus

  • Limiting aw's of Selected Microbes Compared to Typical Food aw's

    aw Selected Food Microbe 0.90 Maple Syrup Most Spoilage Bacteria

    0.88 Most Spoilage Yeasts

    0.84-0.92 S. aureus

    0.83-0.87 Fermented Sausages

    0.82-.94 Jelly

    0.80-0.90 Aspergillus flavus

    0.79-0.84 Fruit Juice Concentrates

    0.8 Most Spoilage Molds

    0.75-0.91 Jams

  • Limiting aw's of Selected Microbes Compared to Typical Food aw's

    aw Selected Food Microbe 0.69 Chocolate Candy

    0.65-0.75 Some Cereals 0.61 Xerophilic Molds /

    Osmophilic Yeasts

    0.60-0.75 Syrups, Sugars 0.54-0.75 Honey

    0.2 Dried Whole Milk

    0.1-0.2 Some Cereals

    Adapted from Jay 1992 and Banwart 1979, Ryser, 1999

  • Approximate Minimum aw for Growth of Certain Groups of Microorganisms Important in Foods

    Most spoilage bacteria 0.90-0.91 Most yeasts 0.87-0.94 Bacillus cereus 0.95 Osmophilic yeasts 0.60-0.78 Clostridium botulinum 0.90-0.98 Most molds 0.70-0.80 Type A 0.95 Xerophilic molds 0.60-0.70 Type B 0.94 Aspergillus 0.68-0.88 Type E 0.97 A. flavus 0.80-0.90 Enterobacter 0.95-0.98 Fusarium 0.80-0.92 Escherichia coli 0.94-0.97 Saccharomyces rouxii 0.62-0.81 Salmonella 0.93-0.96 Staphylococcus aureus 0.84-0.92 Vibrio parahaemolyticus 0.93-0.98 Halophilic bacteria 0.75

    Adapted from Banwart, 1979

  • Impact of aw on growth of Staphylococcus aureus

    Banwart, G. J. 1