NU FS 363 Midterm 1

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NU FS 363 Midterm 1
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NU FS 363
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  1. What does TOTE stand for
    Take out to eat foods
  2. Why is the consumer important in the food supply
    Demands new foods and convenience foods

    Market is often driven by consumer opinions, whether they are correct or not (assumptions of health benefits and negatives - food irradiation greatly reduces risk of foodborne disease, but consumers oppose it because they assume food will be radioactive)
  3. Define GMO
    genetically modified organisms
  4. What are the hazards in the food supply (6)
    • Microbiological
    • Nutritional concerns
    • Environmental contamination
    • Natural toxins
    • Pesticide residues
    • food additives
  5. What are three government agencies that regulate the food supply?  USA?
    • Health Canada
    • -Food and Drug Act Regulations
    • Canadian Food Inspection Agency (CFIA)
    • -Food inspection
    • Agriculture and Agri-Food Canada
    • -Standards for agricultural products
    • USA
    • -FDA, FSIS, USDA
  6. Sum the history of food preservation (product and year)
    • Beer production
    • -7000 BC
    • Wine fermentation
    • -3500 BC
    • Salting and drying
    • -3000 BC
    • Smoking
    • -1000 BC
  7. Who invented canning?  What year?
    Nicholas Appert in 1810
  8. What was Pasteurs contribution
    He found that bacteria sours milk (1857)

    Heat destroys bacteria in wine and beer (1860)
  9. What was Koch's contribution to food microbiology?
    • Links bacteria and disease (1876)
    • -Koch's postulates
  10. What was Lister's contribution to food microbiology?
    • Lactic acid bacteria ferment milk and the concept of aseptic technique/antiseptic
    • (1878)
  11. Who discovered E. Coli? What year?
    Theodor Escherich in 1885
  12. When was the first commercial facility for irradiation of food around
    1967
  13. In what year were foodborne pathogens recognized
    1975 to present
  14. Correctly write salmonella
    Salmonella enterica serovar Typhimurium

    Genera species subspecies then type or serovar
  15. Correctly write e coli
    Escherichia coli 0157:H7
  16. What are microorganisms found in foods (5)
    • Bacteria
    • yeast
    • molds
    • viruses
    • parasites
  17. What are sources of contamination of food (7)
    • Soil
    • Animal Feed
    • Intestinal tract of humans and animals
    • -meat, vegetable or water contamination
    • Water
    • Human human
    • utensils (cross contamination)
    • Air, dust
  18. What is a bacteria that can be found in vacuum packaged hot dogs
    Listeria monocytogenes
  19. What is the term for bacteria associated with food
    Chemoheterotrophs
  20. What is a Chemoheterotroph?
    • A bacteria associated with food
    • Use organic compounds as a source of energy
  21. What do bacteria need for growth (9)
    • Water,
    • Carbohydrates (glucose)
    • Nitrogen source (amino acids, ammonia, nitrite)
    • Potassium
    • Magnesium
    • Iron
    • Calcium
    • Trace elements
  22. What is likely to limit growth of bacteria
    pH, available water.

    Growth is unlikely to be limited by nutrient composition of food.
  23. Why is packaging important in extending storage life?
    It has a modified atmosphere.
  24. What are the four phases of the microbial growth curve, and what are the two axis?
    • Y: log CFU/g
    • X: Time

    • Lag phase
    • Exponential growth phase
    • Stationary phase
    • Death
  25. What does growth rate help microbiologists determine?
    • How fast a food might spoil
    • how fast a food ferments
  26. What are a couple of important parameters that food microbiologists use for bacteria to determine food spoilage
    • Generation time
    • Growth rate
  27. What is the generation time
    • It is the time required for a population bacteria to double
    • It is a reflection of how fast a culture will grow useful for comparative purposes
  28. What is the equation for generation time
    • GT = (T x 0.301)/(log Nt - log N0)
    • 0.301 = log of 2 for doublings
  29. What is the equation to find the number of generations in a bacterial population
    n=T/GT (time over generation time)
  30. What is the first thing someone should do when culturing bacteria
    • Call your mum
    • tell her about the yeast infection
    • Gram stain
  31. What are the possible results of a gram stain? Explain why there are differences and what it means?
    • A gram positive bacteria will stain purple.  They have no outer wall but a thick layer of peptidoglycan. 
    • Gran negative bacteria stain pink.  They have an outer cell wall and a thin layer of peptidoglycan
  32. What are the 5 steps of the gram stain procedure
    • 1. Gently heat fix culture smear by passing slide through flame
    • 2. Flood slide with crystal violet for 1 min.  Wash slide gently. (all cells purple)
    • 3.Flood slides with iodine solution for 3 mins (all cells still purple)
    • 4. Decolorize slide with alcohol for 30 seconds (gram neg cells will lose purple colour)
    • 5. Counterstain with safranin for 1-2 mins (gram positive will be purple)
  33. Describe a yeast
    Nonfilamentous, unicellular fungi
  34. How do yeast reproduce
    • Sexual through binary fision
    • or
    • asexual reproduction through budding
  35. Describe molds
    • Filamentous
    • Grow over a range of temperature and moisture.
    • Exhibit septate hyphae
    • Sporulating and spread by air currents
  36. What type of yeast is important for food spoilage?  What else is it important in
    • Saccharomyces
    • key for brewing and baking
  37. What are molds most likely to cause disease in
    Cheese and other fermented products
  38. How do molds cause disease in humans
    Mycotoxins
  39. What foods to viruses grow in
    They do not grow in food
  40. What viruses can be transmitted through foods
    Hepatitis A and norovirus
  41. What foods to parasites grow in
    They do not grow in foods
  42. What do parasites need to grow
    A host
  43. Name a common parasite from flesh-eating animals
    Trichinella spiralis
  44. How are parasites controlled
    • Cook meat to above 65 degrees celcius.
    • -Internal temp of 70 gives safety margin

    Some cysts destroyed by freezing
  45. How do protozoa survive outside of a host
    Cysys and oocysts
  46. Name an example of protozoa
    • Entamoeba histolytica
    • Giardia lamblia
    • Cryptosporidium parvum
  47. What does food spoilage relate to?
    Food composition
  48. Describe the food spoilage of different food compositions.
    • Lipids = rancidity
    • * oxidative (peroxides etc.) chemical
    • * Hydrolytic (free fatty acids) microbial

    • Proteins = proteolysis (microbial)
    • *putrefaction = ammonia, H2S amines

    • Carbohydrates = fermentation (microbial)
    • *organic acids = souring
  49. How does raw meat spoil?
    Protein degradation if stored in oxygen
  50. how does bread spoil?
    Mold growth
  51. How does oil spoil?
    • Rancidity due to oxidation
    • NOT MICROBIAL
  52. How does yogurt spoil?
    Production of too much acid; mold growth
  53. What is the term for a food with a shelf life
    Perishable foods
  54. what is the storage life of perishable foods
    90 days
  55. What has to be on the packaging of packaged foods? retail foods?
    • a.) BBD
    • b.) Packaged on date
  56. What does a best before date indicate
    How long the product will maintain its quality for.
  57. What percentage of foodborne disease incidents are reported?
    Less than 10%
  58. What are two mechanisms of foodborne illness. Describe the mechanisms
    • Intoxication
    • -toxin produced in the food is ingested and causes illness
    • Infection
    • -organism is consumed and colonizes GI tract and subsequently causes illness.
  59. Name four organisms involved in intoxication and foodborne illness. (one is a mold)
    • Bacillus cereus
    • Clostridium botulinum
    • Staphylococcus aureus
    • Aspergillus flavus (mold)
  60. Name five types of microbes that cause foodborne illness through infection
    • Campylobacter jejuni
    • Enteropathogenic Escherichia coli
    • Enterohemorrhagic Escherichia coli
    • Listeria monocytogenes
    • Salmonella species
  61. What percentage of the food market is composed of fermented foods.  Provide examples
    • 25%
    • Lactic fermentations (cheese, meat, pickles, wine, yogurt)
    • Yeast fermentations (beer, bread, wine)
    • Mold fermentations (cheese, meat, soy)
  62. What the term used to describe production of gas in a vacuum pack.
    Blown pack spoilage
  63. What could cause blown pack spoilage in fresh meat
    • Gas producer
    • *Carb content very low
    • *protein
    • *Not usually metabolized to produce gas
    • Strict anaerobe
    • Psychrophile (optimum growth temperature under 20 because of refrigeration)
    • Doesn't grow well in presence of other organisms (other organisms very low according to plate count)
    • Survives antimicrobial treatments used in meat processing

    • Clostridium putrefaciens
  64. What class of bacteria will grow in a sandwich product and cause blown pack spoilage? why?
    (assuming no odor)
    • Lactic acid bacteria
    • Cheese, meat in sandwich.  Not protein because no odor.
    • Environment is low oxygen and high carbs.
    • Some LAB will produce gas from carbs
  65. What does total cell count tell us about a product? What doesn't it show?
    • It directly counts cells and is viable
    • It can indicate spoilage, by sheer number but does not indicate food safety.
    • Gives cell numbers but not diversity.
    • Changes in number in the processing plant can indicate something has gone wrong.
  66. What do we grow cells in for a plate count
    Plate count agar (PCA)
  67. What class of bacteria can grow in a high 02 environment
    • Gram positive bacteria
    • Gram negative bacteria cant grow
  68. What do lactic acid bacteria like to use for food?
    Sucrose because it is very fermentable
  69. What is the standard incubation temperature of total plate count agar?
    37 degrees
  70. Describe Pour plating
    Take one ml of sample into bottom of petri dish.  Add sterile medium and mix gently but well.
  71. Describe spread plate
    0.1 ml of sample on surface of prepoured agar plate.  Spread sample evenly over surface.
  72. What do you need to do with a solid sample to plate it?
    Blend it with a diluent
  73. Describe the two diluent types
    • Blender: need to sterilize bag and reuse,
    • Stomacher: can dispose of the bag after
  74. What are advantages and disadvantages of the pour plate
    • Advantage: Don't have to have media pre-prepared
    • Disadvantage: Have to have molten media (45 degrees).  Refrigerated organisms have a low yield.
  75. What are advantages and disadvantages of spread plates?
    • Advantage: can buy them.  Cool enough so they do not kill organisms.
    • Disadvantage: expensive
  76. Describe serial dilutions
    always done in 1:10 intervals.  Take 1ml of sample and 9ml of diluent.
  77. What is the minimum number of cells required for accuracy
    20-30 CFU/plate
  78. What is selective media
    Selects for one type of bacteria.
  79. Describe the difference between plating and enrichment
    • Plating=estimate number of cells/g or mL of food. 
    • Enrichment = selective broth
    • *allows growth of specific organism
    • *presence or absence only (does not give number)
    • *often used for detection of pathogens
  80. What type of plating is commonly used for detection of pathogens
    Enrichment plating.
  81. What does the epidemiology of foodborne disease attempt to do
    • Identify cause
    • Determine mode of transmission
    • Evaluate method of control
  82. What is the sequence of events for foodborne disease
    • Organism must contaminate food
    • One of the following must happen:
    • - Organism or toxin must survive storage and processing
    • -Organism allowed to multiply (maybe)
    • Sufficient quantities contaminated food eaten
  83. Which foodborne pathogens have decreased since 1989?  Which one has increased? Why?
    • Increased:
    • Salmonella spp.
    • Staphylococcus aureus
    • Clostridium perfringens


    In 2006 Campylobacter jejuni was starting to be regulated and appeared to increase because it was being reported.
  84. What are important causes of foodborne illness in Canada (11)
    • Salmonella
    • Staphylococcus aureus
    • Clostridium perfringens
    • Campylobacter jejuni
    • Norovirus
    • Bacillus cereus
    • Escherichia coli
    • Shigella
    • Yersinia enterocolitica
    • Clostridium botulinum
    • Listeria monocytogenes
    • Vibrio parahaemolyticus
  85. What is the food category that is the most responsible for foodborne disease
    Plants
  86. What is HACCP
    Hazard Analysis Critical Control Point
  87. What is CFIA
    Canadian Food Inspection Agency
  88. What is FSEP
    Food Safety Enhancement Program
  89. What is CCP
    Critical Control Point
  90. What is GMP
    Good Manufacturing Practices
  91. What is SOP
    Standard Operating Practices
  92. What is FDA
    • Food and Drugs Act (Canada)
    • Food and Drug Administration (US)
  93. What are the benefits of implementing HACCP
    • Maximize product safety
    • *Identifies hazards - eliminate or control to an acceptable level
    • Improve product quality
    • *by-product of improved controls and consistency
    • Improve operational efficiency, profitability
    • *Standard procedure, record keeping control over product
    • Increased customer confidence/demand
    • *Increased awareness of food recalls.
    • Market access/international trade and equivalence
    • *same 7 principles apply to differing systems
    • Legal liability
    • *useful in defense of due diligence
  94. At what government level is HACCP granted at? By who?
    Federal level by CFIA
  95. What is the ISO 9000 quality system
    A quality management system aimed primarily at preventing any non conforming product during production and distribution

    • Write what you do
    • Do what you write
    • prove it
    • (improve it if necessary)
  96. Describe HACCP
    Identifies specific hazards and installs preventative measures

    A science based systematic, preventative approach to controlling food safety that targets resources to critical areas of the process.
  97. What is the purpose of FSEP
    The Food Safety Enhancement Program was developed to assist processing plants with the development and implementation of the HACCP System.
  98. What are the prerequisite programs for HACCP (7)
    • All of the following 7 practices/procedures are carried to favor the production of safe food but focus on environment
    • Premises
    • Transportation, purchasing, receiving, shipping and storage
    • Equipment
    • Personnel
    • Sanitation and pest control
    • Recall
    • Allergen control
  99. What is the difference between a prerequisite program and HACCP
    Prerequisite program focuses on the environment while HACCP is about the food product.
  100. What are samples placed in for dilutions
    0.1% sterile peptone water
  101. Describe the premises prerequisite program
    • Building exterior
    • *Outside property and building maintained
    • Building interior
    • *Design, construction and maintenance
    • *Lighting, ventilation, waste disposal, inedible areas
    • Sanitary facilities
    • *Employee facilities
    • *Equipment cleaning and sanitizing facilities
    • Water quality and supply
    • *Water re-circulation
    • *back-flow control
    • *must be potable
  102. Describe the transportation, purchasing/receiving/shipping and storage prerequisite system
    • Transportation
    • Purchasing/Receiving/Shipping and Storage
  103. Describe the equipment prerequisite program
    • General equipment
    • *Design and installation
    • *Maintenance and calibration
  104. Describe the personnel prerequisite program
    • Training
    • General food hygiene program
  105. Describe the sanitation and pest control prerequisite program
    • Sanitation program
    • *water temperature requirements, chemical concentrations to be used, verification program, procedures and frequencies for cleaning and sanitizing
    • Pest control
    • *written program, pesticide usage log, service reports, corrective actions, verifications
  106. Describe the Recall system of the perquisite program
    • Recall Plan
    • Product coding and labeling
  107. Describe the allergen control of the prerequisite program
    Allergen control program
  108. What must occur with prerequisite programs
    • They must be monitored
    • *Who, what are they doing, how often, how do they do it, standard to be met and records must be kept.
    • Deviation procedures must be outlined.
  109. What are the three questions HACCP answers
    • What are the hazards associated with my product?
    • Where do these hazards occur?
    • How can I control or eliminate these to an acceptable level?
  110. What are the 7 principles of HACCP
    • Conduct a hazard analysis
    • Determine critical control points
    • Establish critical limits
    • Establish monitoring procedures
    • Establish deviation procedures
    • Establish verification procedures
    • Establish record keeping (for points 1-6)
  111. What are the 12 steps to developing a HACCP plan
    • 1. Assemble your HACCP team
    • 2. Describe your product and identify its intended use (Form 1)
    • 3. List product ingredients and incoming material.
    • 4. Construct a process flow diagram and a plant schematic (Forms 3 and 4)
    • 5. Verify, on site, your process flow diagram and plan schematic
    • 6. List the hazards associated with each step and incoming material in your plant's process (principle 1)
    • 7. Apply the HACCP decision tree to determine CCPs (Principle 2)
    • 8. Establish critical limits (Principle 3)
    • 9. Establish monitoring procedures (Principle 4)
    • 10. Establish deviation procedures (Principle 5)
    • 11. Establish verification procedures (Principle 6)
    • 12. Establish record keeping and documentation procedures for principles 1 through 6 (Principle 7)
  112. Describe form 1
    • Step 2 of the HACCP plan
    • Describes product and identifies its intended use
    • Product name, important characteristics, how the product will be used, packaging, shelf life, where it will be sold, labeling instructions, special distribution control
  113. Describe form 2
    Lists product ingredients
  114. Describe form 3
    • Process flow diagram
    • - Includes steps from receiving to final shipping
    • - Product specific
  115. Describe form 4
    • Plant schematic
    • Shows product flow and employee traffic flow
  116. What is hazard analysis?
    • It is an essential part of HACCP
    • Every ingredient and step of a process is analyzed to determine what hazards are present
    • The hazards are controlled, reduced or eliminated
  117. What are the classes of food safety hazards (3)
    • Biological
    • *bacterial pathogen
    • *parasites
    • *Viruses
    • Chemical
    • *Natural toxins
    • *Drugs
    • *Chemicals
    • *Allergens
    • Physical
    • *Metal
    • *Glass
    • *Foreign Object
  118. Describe form 8
    • Associated with principle 2 of HACCP (step 7).
    • Determines critical control points
  119. What are the three most common critical control points?
    Cooking, chilling or refrigeration and formulation control
  120. What are the differences between prerequisite and CCP.  What about process control?
    • Prerequisite: Indirectly deal with food safety issues, More general - not product specific and non-compliance rarely results in action against the product
    • CCP: Directly deals with food safety issues, product specific and non-compliance results in action against product
    • Process control: An activity that enhances the ability of a CCP to be effective, must be linked to a specific hazard and CCP, often used in slaughter.
  121. What is a critical limit
    • It is one or more prescribed tolerances that must be met to ensure that a CCP effectively controls a hazard.
    • The limits may meet government regulations or company standards.
  122. Describe Form 10
    establishes critical limits and is associated with principle 3 and step 8 of the HACCP protocol.
  123. What is monitoring
    A planned sequence of observations or measurements of critical limits designed to produce and accurate record and is intended to ensure that the critical limit maintains product safety.
  124. Describe Form 10
    establishes monitoring procedures, deviation procedures, verification procedures and record keeping. It is associated with principles 4-7 and steps 9-12 of HACCP
  125. What is deviation
    Failure to meet the required critical limits defined for a CCP
  126. What is verification
    Methods, procedures and tests used to determine if the HACCP system is valid and operating properly
  127. Describe records of HACCP
    in-plant documentation that is kept for each CCP required to ensure that the HACCP plan is followed.
  128. Describe form 11
    • It is the new step for FSEP program - process controls
    • Multiple steps help reduce the single hazard Always linked to subsequent CCP
    • Must be validated by processor to demonstrate that PC is effective in reducing hazards
    • Monitoring, deviation procedures and verification procedures must be in place for PC
  129. What are extrinsic factors
    • Factors that can be controlled
    • Factors in the environment external to the food, which affect both the microorganisms and the food itself during processing and storage
    • 1. Temperature
    • 2. Gaseous environment
  130. What is the single most important factor to control the rate of growth of microorganisms
    Temperature
  131. What are important concepts to consider regarding temperature as an extrinsic factor
    • Minimum growth temperature
    • Optimum growth temperature
    • Maximum growth temperature
  132. What is the chemistry kinetics rule of thumb
    The reaction rate doubles with every 10 degree temperature increase (until it reaches a limit when protein degradation occurs)
  133. What type of testing should not be used for food and why
    Microbial testing because it takes too long
  134. Why is minimum growth temperature important
    Because it is important in determining growth location
  135. What is the danger zone and why is it important
    • It is a key concept in food spoilage and safety.
    • It is from 4.4 degrees to 60 degrees.  Growth of pathogens have been selected to grow at body temperature.  Any food exposed to the danger zone for two hours it at risk.
    • Spoilage of food will occur if exposed to the danger zone
  136. What is a Psychrophile
    An organism that grows at temperatures of 20 degrees or less.  Not common in food except in some fish.
  137. Provide an example of a Psychrophile that may be common in food
    Vibrio spp.
  138. What is a Psychrotroph
    An organism with its optimum at around 30 degrees.  Grows at refrigeration temperatures, optimum growth of 20 degrees.
  139. What is a mesophile
    An organism with an optimum temperature of 35 degrees or higher.  Minimum growth of 7 to 10, and max growth of 40-60.
  140. What is a psychrotroph that is common in food
    Listeria monocytogenes
  141. what is a mesophile that is common in food
    Escherichia Coli and Staphylococcus aureus
  142. What is a thermodurics
    An endospore forming bacteria that survive but do not grow at temperatures over 60.  Pretty much the same as Mesophiles, but have endospores.
  143. What is a thermoduric that is common in food
    Bacillus spp. and Clostridium spp.
  144. What is a thermophile
    An organism that grows at temperatures above 45 (optimum).  Not common in foods, but some organisms grow and high temperatures.
  145. What is a thermophile that is common in food.
    Thermophiles are not common in food.  Streptococcus thermophilus may be apparent because of boiling of soup.
  146. Describe the temperature chart of bacteria
    • 121 degrees - destruction of bacterial endospores
    • above 100- all cells killed, only achieved with pressure/temp combinations
    • above 80 - vegetative cells killed
    • 60-4.4 danger zone (active growth)
    • Below -20 destruction of some parasites
  147. At what temperature does death of viable cells occur
    Death of viable cells starts to occur after 60 degrees
  148. What temperature should hot foods be stored at
    Above 60 degrees
  149. What temperature should cold foods be stored at
    Below 4 degrees
  150. Name three pathogens that grow under 4
    • Listeria
    • Clostridium botulinum
    • Yersinia enterocolitica
  151. What is a difference between bacterial spores and fungal spores
    ndospores are resistant to heat, drying and disinfecting chemicals

    Fungal spores are not heat resistant
  152. Why is the gaseous environment important in terms of extrinsic factor for microbial growth
    Primarily comparing difference between aerobic and anaerobic storage
  153. Describe aerobic storage and types of bacteria that grow
    • Primarily gram-negative, non-sporeforming, rods (pseudomonads)
    • Oxidative and breakdown fats and proteins = odors
  154. At what concentration of CFU are odors detectable in aerobic storage in meat.  Why is there an odor?
    Oxidative and breakdown fats and proteins.  Odors are detectable at 10^6 to 10^7 CFU/g of meat.
  155. Describe anaerobic storage in terms of extrinsic factors.
    • Usually with carbon dioxide
    • Modified atmosphere or vacuum packed
    • Usual bacteria are gram-positive lactic acid bacteria.  Fermentative and convert sugars to lactic and acetic acid
  156. What is a key difference between the detection of spoilage in aerobic and anaerobic bacteria?
    • Aerobic bacteria produce odors because of oxidation and breakdown of fats and proteins.  This signifies spoilage
    • Anaerobic bacteria ferment sugars to lactic and acetic acid.  Spoilage is only detected after max population is reached.
  157. What takes longer to spoil, anaerobic or aerobic bacteria?
    Anaerobic bacteria because they do not produce an odour.
  158. How can you preserve microbes
    Freeze them to -80 and use glycogen stocks for preservation
  159. What is the relationship between pressure and boiling point?
    When pressure increases, the boiling point increases
  160. What is Josh
    A Whitneyphile <3
  161. What determines the dominant population of a colony
    It is related to the ideal population of bacteria and environmental conditions
  162. What are the five intrinsic factors
    • Physical structure
    • Nutrients and natural inhibitor
    • pH
    • Water Activity
    • Redox Potential
  163. Describe the physical structure of intrinsic factors
    • Idea that microbes reflect structure
    • Physical barriers can prevent contamination of bacteria.  (outside of meat and fruits)
    • parasites can dig through the structure
  164. Describe the nutrient and natural inhibitor of intrinsic factors
    • Does the food have everything necessary for growth
    • Are nutrients available microbially?
    • Primary concept - how rich is the growth environment in terms of the nutrients

    Enzymes produced by a microorganism influence its ability to utilize different energy sources.
  165. What does fastidious mean
    Bacteria require amino acids and or vitamins and growth factors
  166. Name two types of natural inhibitors and how they work
    • Lysozyme, found in egg whites, hydrolyses peptidoglycan
    • Hops in beer produces humulones which is a strong antimicrobial preventing lactic acid bacteria from doing anything to the yeasr
  167. Describe pH in terms of intrinsic factors
    • Using pH as a control mechanism
    • Usually acidic range
  168. Recopy the intrinsic factor pH table
    Go to lecture 8 notes
  169. Why isn't food used stored at alkaline pH?
    Breaks down food and effects food quality
  170. Describe the succession of species in regards to pH
    • Starts off neutral pH
    • Streptococcus lactis uses nutrients early on and reaches stationairy phase.  When it starts to die because of decreasing pH because of fermentation, Lactobacilli spp. begins to grow because they are not in competition.  They drive the pH down, and then film yeasts oxidize the lactic acid and return pH to normal.
  171. What is an indicator of osmotic strain
    Water activity
  172. Describe water activity of intrinsic factors
    Water activity is simply the ratio of the water vapor pressure in any kind of food system to the water vapor pressure of pure water
  173. Why is water activity important
    Water activity is used for compliance of government regulations, CFR, HACCP and other food safety programs.

    Upper and lower level water activity measurements establish qualities for food products including: texture, microbial, flavor, appearance, aroma, cooking.
  174. Know water activity chart
    Lecture 8
  175. What is inhibited at water activity of 0.85
    Staphylococcus aureus
  176. At what water activity can most pathogenic bacteria been inhibited at?
    0.92
  177. At what water activity are yeasts and molds stopped at?
    0.7-0.75
  178. What are three activities decrease water activity
    • Drying
    • Salt
    • Cold
  179. What is osmotic dehydration
    The moisture transfer process which occurs during the salting of fish or cheese etc.  The food is surrounded by a solution with lower water activity.
  180. Define halotolerant
    high salt concentrations
  181. Define osmotolerant
    High concentration of organ compounds (sugars)
  182. Xerotolerant
    Growth on dry foods
  183. What is redox potential of intrinsic factors
    • Oxidation - reductions basis for almost all biological reactions
    • Growth reduces redox potential
  184. What is the relationship between redox potential and growth
    Growth reduces redox potential
  185. What is an oxidizing agent? Reducing agent?
    • Oxidizing agent accepts electrons
    • Reducing agent donates electrons
  186. What is Lestner's Hurdle concept
    a bacteria might be able to overcome different challenges.  if it can not overcome the challenge then it dies.  Multiple challenges at the same time is more difficult to overcome.

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