food microbiology fdt 3301

1. FOOD MICROBIOLOGYFDT 3301/5301 Mindy Brashears, Ph.D. Assistant Professor of Food Safety and HACCP

3. A Brief History Early Food Preservation 900 AD � �Food Poisoning� Recognized 1795-Appert Developed Canning 1854-1864-FOOD MICROBIOLOGY BECOMES A SCIENCE Louis Pasteur Food Preservation Methods Cheese, Beer, Bread, Sauerkraut, Summer Sausage 900 AD Food Poisoning Recognized Emperor Leo VI of Byzantium issued an edict that forbade eating blood sausage prepared by stuffing blood into a pig stomach and preserving it by smoking-BOTULISM Greeks and Romans - 1582 Ergotism, Claviceps purpurea � Rye Food Poisoning was Recurrent because we didn�t know what caused Appert � Food in jars and boiled to preserve, but did not know WHY? 1795 �agents of putrefication� or �fermentable principles� 1854-1864 � Louis Pasteur � discovered scientific basis for preservation methods-FOOD MICRO BECOMES a SCIENCE �pasteurization� � First done in Wine, now milk, juices, etc. Food Preservation Methods Cheese, Beer, Bread, Sauerkraut, Summer Sausage 900 AD Food Poisoning Recognized Emperor Leo VI of Byzantium issued an edict that forbade eating blood sausage prepared by stuffing blood into a pig stomach and preserving it by smoking-BOTULISM Greeks and Romans - 1582 Ergotism, Claviceps purpurea � Rye Food Poisoning was Recurrent because we didn�t know what caused Appert � Food in jars and boiled to preserve, but did not know WHY? 1795 �agents of putrefication� or �fermentable principles� 1854-1864 � Louis Pasteur � discovered scientific basis for preservation methods-FOOD MICRO BECOMES a SCIENCE �pasteurization� � First done in Wine, now milk, juices, etc.

4. Why Study Food Microbiology? Provide Clean, Safe, Healthful Food to Consumer Food Permits Growth Control of Microbial Growth Prevent Food Spoilage Prevent Food-borne Illnesses Food Preservation and Production Microbial Characteristics -Food permits growth of bacteria � high in nutrients, water, etc. We need to control this growth in some circumstances Some are useful!!! Microorganisms are Commonly Found in Foods: Sources Environmental Animals � Dirt, Feces, Hide, Digestive Tract, etc. Fruits and Vegetables � Fertilizer, Birds, Wild Animals, etc. Grains � Molds Control: Economic and Public Health Issues Microbial Characteristics -Food permits growth of bacteria � high in nutrients, water, etc. We need to control this growth in some circumstances Some are useful!!! Microorganisms are Commonly Found in Foods: Sources Environmental Animals � Dirt, Feces, Hide, Digestive Tract, etc. Fruits and Vegetables � Fertilizer, Birds, Wild Animals, etc. Grains � Molds Control: Economic and Public Health Issues

5. Food-Borne Illness ERS Estimates $6.9 Billion/Year Cost of FBI CDC Estimates 76 Million Cases of FBI Annually 325,000 Hospitalizations 5,000 Deaths

6. What Organism Causes the Most Cases of Food-Borne Illness Annually? CampylobacterCampylobacter

7. What Organism Causes the Most Deaths Due to Food-Borne Illness? SalmonellaSalmonella

8. Review of Microbiology Mostly Single Celled Groups Morphologies Gram Reactions Size Growth Rate Groups of Microorganisms Bacteria Yeasts and Molds � Fungi Viruses Rickettsiae Algae Protozoa Focus on Bacteria, but will touch on others. Morphologies Rods, straight, curved, spiral, club Cocci, Chains (strep), clusters (staph) If you see chains then the organism probably grew in the food. Gram + or Gram -. 1-5 um long � to 1 um wide Growth- Binary Fission Elongation and then Split Can be as fast as 20 minutes Groups of Microorganisms Bacteria Yeasts and Molds � Fungi Viruses Rickettsiae Algae Protozoa Focus on Bacteria, but will touch on others. Morphologies Rods, straight, curved, spiral, club Cocci, Chains (strep), clusters (staph) If you see chains then the organism probably grew in the food. Gram + or Gram -. 1-5 um long � to 1 um wide Growth- Binary Fission Elongation and then Split Can be as fast as 20 minutes

9. Exponential Growth 30 Minute Generation Time Time 0 1000/g 30 min 2000/g 1 hour 4000/g ��.. 5 hours 1,000,000/g

10. Microbial Growth Phases Growth Curves Plotted on log paper Log10 of Count vs. Time A-Lag. Increase Lag Phase to Prevent Food Spoilage. Microorganisms adjusting to new environment B-Log. C-Stationary. Build up of toxic materials and other factors. D-Death Phase 1 x 10^9 is maximum growth of most microorganisms Growth Curves Plotted on log paper Log10 of Count vs. Time A-Lag. Increase Lag Phase to Prevent Food Spoilage. Microorganisms adjusting to new environment B-Log. C-Stationary. Build up of toxic materials and other factors. D-Death Phase 1 x 10^9 is maximum growth of most microorganisms

11. Intrinsic and Extrinsic Factors Intrinsic pH Moisture Content Oxidation-reduction Potential Nutrient Content Antimicrobial Constituents Biological Structures Intrinsic-�parameters of plant and animal tissues that are an inherent part of the tissues�� Jay, 2000 Intrinsic-�parameters of plant and animal tissues that are an inherent part of the tissues�� Jay, 2000

12. pH Effects of pH Enzymes Nutrients Other Environmental Factors Temperature Salt Age No known pathogen grows below pH of 4.6 Clostridium botulinum pH Optimal � 6.6-7.5 Other considerations 1. Type of Acid Citric. Hydrochloric, phosphoric, and tartaric acid permit growth at lower pH than acetic or lactic Yeast and Molds can grow at lower pH. Acidic Foods-fruits, soft drinks, vinegar,wines 2. Buffering capacity-ability to resist changes in pH Ie meats have high buffering capacity pH Effects 2 Aspects Functioning of Enzymes Transport of Nutrients In acidic environments, the cells must keep H+ ions out or pump out H+ ions. DNA and ATP require neutrality to function Transport of nutrients Environmental Factors Temperature pH becomes more acid when Temp increases Salt Salt can broaden the pH growth range of some mo�s, but when concentration exceeds optimal levels then the growth range can be narrowed Age Young cells more susceptible No pathogen grows below pH of 4.6 � C. bot. pH <3.5 Citrus fruits, pickles, kiwi, condiments (mayo) pH 6-7 Meat,milk, corn, vegetables, eggs Molds and Yeast more tolerant of pH extremes Molds 0-11 Yeast 1.5 to 8.5 pH Optimal � 6.6-7.5 Other considerations 1. Type of Acid Citric. Hydrochloric, phosphoric, and tartaric acid permit growth at lower pH than acetic or lactic Yeast and Molds can grow at lower pH. Acidic Foods-fruits, soft drinks, vinegar,wines 2. Buffering capacity-ability to resist changes in pH Ie meats have high buffering capacity pH Effects 2 Aspects Functioning of Enzymes Transport of Nutrients In acidic environments, the cells must keep H+ ions out or pump out H+ ions. DNA and ATP require neutrality to function Transport of nutrients Environmental Factors Temperature pH becomes more acid when Temp increases Salt Salt can broaden the pH growth range of some mo�s, but when concentration exceeds optimal levels then the growth range can be narrowed Age Young cells more susceptible No pathogen grows below pH of 4.6 � C. bot. pH <3.5 Citrus fruits, pickles, kiwi, condiments (mayo) pH 6-7 Meat,milk, corn, vegetables, eggs Molds and Yeast more tolerant of pH extremes Molds 0-11 Yeast 1.5 to 8.5

13. Moisture Remove and/or Bind Moisture Humectants Dehydration Water Activity � Aw Most Fresh Foods - Aw > 0.99 One of the oldest methods of preservation is drying/dessication Humectants � Salt, sugar, proply glycol Dehydration � Remove Water/Dry Water Activity � Amount of Water available for Chemical reactions and microbial growth ratio of the water vapor pressure to the vapor pressure of pure water at the same temperature A2 � p/po P= Vapor pressure of the solution Po= Vapor pressure of the solvent (water) Related to Relative Humidity RH+100 x Aw20 Pure Water Aw=1.00 22% NaCl Solution = 0.86 Saturated NaCl Solution = 0.75 Spoilage Bacteria 0.91 Spoilage Yeasts 0.88 Spoilage Molds .80 One of the oldest methods of preservation is drying/dessication Humectants � Salt, sugar, proply glycol Dehydration � Remove Water/Dry Water Activity � Amount of Water available for Chemical reactions and microbial growth ratio of the water vapor pressure to the vapor pressure of pure water at the same temperature A2 � p/po P= Vapor pressure of the solution Po= Vapor pressure of the solvent (water) Related to Relative Humidity RH+100 x Aw20 Pure Water Aw=1.00 22% NaCl Solution = 0.86 Saturated NaCl Solution = 0.75 Spoilage Bacteria 0.91 Spoilage Yeasts 0.88 Spoilage Molds .80

14. Microbial Growth and Aw Halophilic 0.75 Xerophilic molds 0.61 Osmophilic yeasts 0.61 Lowest Aw for Pathogen Growth 0.86 Stapholococcus aureus Halophilic � Salt Loving - Vibrio Xerophilic � Dry Loving Osmophilic � Survives High Osmotic Pressure No pathogen survives below 0.86 Stapholococcus aureus survives, but does not growHalophilic � Salt Loving - Vibrio Xerophilic � Dry Loving Osmophilic � Survives High Osmotic Pressure No pathogen survives below 0.86 Stapholococcus aureus survives, but does not grow

15. Oxidation- Reduction Potential O/R Potential - Eh ��ease with which the substrate loses or gains electrons.� Loss of electrons � oxidized Gain of electrons � reduced Aerobic Anaerobic Microaerobic Facultative anaerobes Aerobic � require positive Eh values � must have oxygen Anaerobic � require negative Eh values � no oxygen Microaerophiles- small amounts of oxygen Facultative anaerobes � both aerobic and anaerobic Eh changes with packaging � canning, MAP, vacuum packagingAerobic � require positive Eh values � must have oxygen Anaerobic � require negative Eh values � no oxygen Microaerophiles- small amounts of oxygen Facultative anaerobes � both aerobic and anaerobic Eh changes with packaging � canning, MAP, vacuum packaging

16. Others Nutrients Fastidius vs non-fastidious Biological Structure Antimicrobial Factors Naturally occurring factors Fastidius � very specific growth requirements Some grow on very little nutrients Bacteria need protein, CHO, fats, vitamins, minerals Structure Shells on nuts and eggs, skins Antimicrobial Factors Naturally occurring substances that prevent microbial growth Lysozyme � Eggs Milk � enzymes active in first 1-2 hours Spices � garlic � allicin cloves - thymol Fastidius � very specific growth requirements Some grow on very little nutrients Bacteria need protein, CHO, fats, vitamins, minerals Structure Shells on nuts and eggs, skins Antimicrobial Factors Naturally occurring substances that prevent microbial growth Lysozyme � Eggs Milk � enzymes active in first 1-2 hours Spices � garlic � allicin cloves - thymol

17. Extrinsic Factors Temperature Relative Humidity Gases in the Environment Presence of Other Microorganisms

18. Temperature Microorganisms grow over a wide range of Temperatures Psychrotrophs Mesophiles Thermophiles Psychroduric Thermoduric Psychrotrophs � grow well below 7 C, optimum at 20-30 C Pseudomonas and Enterococcus Responsible for spoilage Mesophiles � grow well 20-45 C, optimum at 30-40 C Most food-borne bacteria fall into this category Thermophiles � grow well at and above 45 C, optimum at 55-65 C Bacillus and Clostridium Psychroduric Survive, but do not grow at low temps Thermoduric Survive, but do not grow at high tempsPsychrotrophs � grow well below 7 C, optimum at 20-30 C Pseudomonas and Enterococcus Responsible for spoilage Mesophiles � grow well 20-45 C, optimum at 30-40 C Most food-borne bacteria fall into this category Thermophiles � grow well at and above 45 C, optimum at 55-65 C Bacillus and Clostridium Psychroduric Survive, but do not grow at low temps Thermoduric Survive, but do not grow at high temps

19. Other Factors Relative Humidity of Environment Can change the Aw Environmental Gasses CO2, Ozone, If Aw is low and RH is high, the food can pick up enough moisture from environment to allow for microbial growth Gasses can be added to package to control/reduce microorganisms If Aw is low and RH is high, the food can pick up enough moisture from environment to allow for microbial growth Gasses can be added to package to control/reduce microorganisms

20. Presence of Other Microorganisms Competitive Exclusion General microbial antagonism Lactic Antagonism Some food-borne organisms produce substances that are inhibitory or lethal to other organisms antibiotics, bacteriocins, hydrogen peroxide, organic acids Sterile foods more susceptable to contamination and uncontrolled growthSome food-borne organisms produce substances that are inhibitory or lethal to other organisms antibiotics, bacteriocins, hydrogen peroxide, organic acids Sterile foods more susceptable to contamination and uncontrolled growth

21. Hurdle Concept Combine Intrinsic and Extrinsic Factors to Control Microbial Growth Combination requires less severe treatments to foods to get desired inhibition