NDFS 250 quiz 3

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NDFS 250 quiz 3
2012-10-10 00:26:19
food science

BYU NDFS 250 quiz 3 fall 2012
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  1. Food Safety Biological
    • •Bacteria, molds,
    • yeasts, viruses, parasites

    • •Biotechnology /
    • genetically modified organisms
  2. Food Safety
    Chemical concerns
    •Food additives

    •Pesticide residues

    • •Lipid oxidation
    • products

    • •Irradiation induced
    • products

    •Nonenzymatic browning products

    • •Pyrolysis products
    • (e.g., from charred meat)
  3. Food Safety 
     Physical concerns
    • •Glass, metal, bone,
    • stones, wood, insects and other filth
  4. Foodborne illness prevalence
    CDC estimates that each year roughly 1 in 6 Americans get sick
  5. Bacteria
    —One-celled microorganism

    —Distinguished by shape: round, rod, spiral or filament

    —May form spores
  6. Yeast
    —One-celled microorganism

    —Oval or spherical shaped 

    —May form spores
  7. Mold
    —Multicellular microorganism

    —Filaments give fuzzy or cotton-like appearance

    —Strict aerobes (need oxygen)

    —May form spores
  8. Thermophiles 
    • —(40 to 70 °C)
    • —Optimum growth at 45°C (113°F) and up.
  9. Mesophiles
    • —(10 to 50 °C)
    • —Optimum growth at 20-45°C (68-113°F)
  10. Psychrotrophs
    • —(0-30 °C)
    • —Can grow at refrigerated temperatures, but optimally grow at higher temperatures

      (some grow slowly even when frozen)
  11. Psychrophiles
    • —(-10 to 20 °C)
    • —Grow well at refrigerated temperatures

    —Capable of growth below 10°C (50°F)
  12. Growth of Microorganisms Oxygen Conditions
  13. Temperature of foods for control of bacteria
    Do not hold between 40 – 140 °F for more than 2-3 hours
  14. General microbial growth requirements 
  15. General microbial growth requirements - Yeasts
  16. General microbial growth requirements - Mold
  17. •Food poisoning/ Intoxication
    •An illness caused by toxin produced by an organism

    •e.g. Staphylococcus sp. toxins
  18. Food-borne infection
    •An illness caused by an organism that grows in G.I. tract

    •e.g., Salmonella sp.
  19. Top five foodborne illness

    • Salmonella
    • Norovirus

    Colstidium perringes

    Campylobacter spp.

    Staph aureus. 
  20. Mycotoxins
    (toxins produced by mold) can be carcinogenic)
  21. Aflatoxin
    —Mycotoxin produced by mold

    —Aspergillis flavus

    —Aspergillis parasiticus

    —Penicillium puberulum

    —Found in certain foods




    —Causes liver cancer in animals

    —20 ppb maximum limit in food
  22. Food Handling Behaviors
    Clean, Seperate, Cook, Chill
  23. Useful purposes served by microorganisms - Mold
    •Soy sauce

    •Roquefort  (blue) cheese

    •Camembert cheese
  24. Useful
    purposes served by microorganisms - Yeast



    •Vinegar (and bacteria)
  25. Useful purposes served by microorganisms - Bacteria


    •Swiss cheese

    •Fermented pickles


    •Vinegar (and yeast) 
  26. Basic causes of food deterioration - •Biological factors
    •Microorganisms (bacteria, yeasts and molds)

    •Infestation (insects, parasites, rodents)
  27. Basic causes of food deterioration - •Chemical factors
    •Nonenzymatic reactions, e.g., lipid oxidation, Maillard browning

    •Enzymatic reactions
  28. Basic causes of food deterioration - •Physical Factors
    •Inappropriate storage temperatures

    •Gain or loss of moisture

    •Reactions with oxygen or light

    •Physical stress or abuse

  29. Food preservation - •Water removal or binding
    •Drying, humectants 
  30. Food preservation - •High Temperature
    •Thermal processing
  31. Food preservation - •Low Temperature
    •Refrigeration, freezing
  32. Food preservation - •Aseptic Conditions
    •Packaging, processing in sterile conditions (free of microorganisms)
  33. Food preservation - •Oxygen Control
    •Vacuum or inert atmosphere packaging
  34. Food preservation - •Chemical Preservatives
    •Antimicrobials, antioxidants
  35. Food preservation - Irradiation 
    Gamma Rays
  36. •Drying
    •Removal of water from a food using ambient conditions

    •Often used as a synonym for dehydration
  37. •Dehydration
    •Removal of water from a food using controlled conditions of heating, forced air circulation, and relative humidity
  38. •Sun-drying
    •Drying in sun with no specific controls.

    •Often done with raisins, prunes, figs, apricots, pears, peaches, grains

    •Causes largest loss of nutrients of any drying method

    Amount of time it takes to dry is draw out if nutrients are being lost at a given right

    Sunlight radiation destroys 
  39. Solar Dryers
  40. •Spray drying
    Spraying liquid into a current of dry, heated air.
  41. Freeze-drying
    •Product is frozen then ice is sublimed to water vapor by pulling a vacuum

    •Expensive but preserves texture
  42. •Drum drying
    •The product is made into a slurry and spread on the surface of a drum heated inside by steam; when it dries, the product is scraped off; may also use a vacuum.

    •Not as economical as spray drying.

  43. •Tunnel drying
    •Dry air is blown cross-current or counter-current at a high velocity around the food; the dry air provides heat and takes away the water.
  44. Deep fat frying (chips) 
    Hot oil replaces hot air as drying medium.
  45. Osmotic dehydration( candy fruit)
    Product tossed in bed of sucrose crystals which pull water from cells.
  46. Extrusion drying (cheese puffs, breakfast cereals)
    Slurry of cereal is passed through heated tube under pressure.  As product exits through a sized opening, sudden pressure release causes water to evaporate. 
  47. Baking ( crackers) 
    Water is vaporized.
  48. Optimizing storage of dehydrated foods 

    • humidity
    • air
    • light
    • temperature
  49. H umdity  (moisture) 
    allows mold growth, accelerates chemical reactions
  50. Air  (oxygen)
    allows mold growth, destroys fats and pigments
  51. Light
    destroys fats, pigments, and some vitamins
  52. Temperature
    accelerates chemical reactions
  53. Most heat resistant food pathogen 
    Clostridium botulinum spores
  54. low acid and acid dividing line 
    pH of 4.6, costridium
  55. Nicolas Appert
    the French inventor of airtight food preservation. Appert, known as the "father of canning"
  56. Peter Durand 
    Peter Durand was a British merchant who is widely credited with receiving the first patent for the idea of preserving food using tin cans
  57. Clostridium Botulinum spore growth
    Anaerobic environment

    pH > 4.6

    aw > 0.92 

    Temperature 3.3 to 97 °C 

    • ¢Protein
    • and/or carbohydrate medium favors growth

    • Low salt content
    •    —Growth is prevented in products with 5-10% salt, e.g., salt-cured meats)
  58. Factors affecting microbial destruction by heat
       More Difficult to Destroy
    •Increased sugar (up to a point)

    •Increased lipid concentration

    •Increased protein concentration

    •0.5 to 3 % NaCl

    •Neutral pH (for most microbes)

    •Higher microbial load
  59. Factors affecting microbial destruction by heat - •Easier to Destroy
    •Longer heating time

    •Higher temperature

    •Will decrease heating time

    •> 3% NaCl

    •Extreme pH
  60. D-Value
    • Time at a given temperature to reduce microbial population of a given
    • population (species) by 90%.
  61. •Sterilization
    •Treatment to destroy all microbes and spores
  62. •Commercial sterilization
    •Treatment to destroy all pathogenic and spoilage organisms

    •May contain some thermophiles
  63. •Pasteurization
    •Treatment to destroy pathogenic organisms

    •Example: Milk

    •Batch: 145oF(62°C)/30 min.

    •HTST: 161oF(72°C)/15 sec.

    •UHT: 280°F(138°C)/2 sec.
  64. •Blanching
    •Steaming or boiling water immersion for a short period of time

    •Inactivates enzymes, usually prior to freezing vegetables
  65. •R enamel 
    • •Red berries, cherries, plums, pumpkin, rhubarb, winter squash, etc. which have red anthocyanin pigments (which react
    • with metal ions)
  66. •C enamel 
    •Corn, hominy which contain S

    •Can made with Sn or Fe

    •If no enamel

    •S +Sn or Fe       SnS or FeS (black)

    •Enamel contains ZnO

    •ZnO + S      ZnS (white)
  67. Purposes of container headspace
    Allows contents to expand

    Helps create a partial vacuum (after processing and cooling)

    Helps maintain seal; assures the consumer that the product is properly sealed
  68. What causes cans to bulge? - Growth of gas producing microbes 
    —Potentially fatal
  69. What causes cans to bulge? - Hydrogen swell

    —Caused by acid in food reacting with metal (iron or tin)

    —Hydrogen gas produced
  70. Retort processing - Retort
    —Large pressure cooker, holding hundreds of cans or other food containers, used to heat process packaged foods
  71. Retort Processing - Venting
    —Removing air from a vessel, especially a pressure cooker or retort.  Ensures the retort contains only steam.
  72. What is the possible consequence of improper venting of a retort prior to timing the processing?
    Process is based on pure steam in the retort

    If not all steam, process may be inadequate to destroy all pathogens
  73. Aseptic Processing
    —Process where food is commercially sterilized, cooled, filled into separately sterilized containers 
  74. Hot fill and hold process
    —Process where hot food is filled into container, sealed, inverted and held before cooling to sterilize lid.

    • —Only used with acid or acidified foods where C.
    • botulinum is not a concern, e.g. jams and jellies.
  75. Sealing temperature - Cans
    —The seal is complete before process

    —Therefore, it is necessary to displace some air so that once the container cools a partial vacuum will develop

    —Air is displaced by steam, thus the need for high sealing temperature (~170 F)
  76. Sealing temperature - Bottles
    —The seal is not complete before the process

    —Air is displaced during processing, thus the sealing temperature does not have to be high.
  77. •Common or cellar storage
    •<15 ºC (Slightly cooler than outside temp.)

    •Short term

    •Root crops, potatoes, cabbage, celery, apples
  78. •Refrigeration
    •0 to 10 ºC

    •Weeks to months

    •Most foods 
  79. •Freezing 
    •< -18 ºC  or 0 ºF

    •Months to 2 years

    •Most foods
  80. •Air freezing
    Air-blast, where frigid air at –18 to –57 °C is blown over food
  81. •Indirect contact freezing
    •Indirect contact, with refrigerant flowing through separate passage. Plate freezer at –18 to –46 °C
  82. •Immersion freezing
    •Direct immersion of food, e.g., liquid N2 at –196 °C and CO2 at    –79 °C
  83. Advantages of low temperature preservation 
    • •Better sensory quality 
    • •Better nutrient
    • retention (in some cases)
  84. Disadvantages
    of low temperature preservation 
    • •Cost  (requires continual input of energy)
    • •Shorter shelf life (compared to canning, drying)
  85. Changes in food during refrigeration / cool storage - Microbial Growth
    •Slowed, but continues
  86. Changes in food during refrigeration / cool storage - •Chemical changes
    •Starch to sugar in potatoes

    •Staling of bread 
  87. Changes in food during refrigeration / cool storage - •Off flavors
    •When stored with certain foods 
  88. Changes in food during refrigeration / cool storage - •Chill injury in some foods
  89. Changes in food during freezing / frozen storage
    • •Formation and growth of ice crystals (texture)
    • •Movement of water from cells(freezer burn)
    • •Microbial load(no major change)
  90. —Freezing rate

    Faster rate gives best texture
  91. —Temperature of frozen storage
    • —-18 °C (0 °F) orbelow
    • —Should not fluctuate 
  92. Freezer Burn
    —Dehydrated surface on a frozen food

    —Small white patches or larger greyish-white blemishes, that are dry, grainy and tough in texture

    —Caused by the sublimation of ice from the surface of the frozen product

    —Fluctuations in freezer temperature (automatic defrost) worsens this problem.
  93. •Frozen Food Packaging
    •Easy to seal plastic, or tight fitting lids

    •Water proof

    •Water vapor proof (or resistant)

    •Low permeability to other gases

    •Durable:  High wet strength, will not become brittle and crack when cold
  94. •Container Size and Headspace
    •Use small containers

    •> 1/2 gallon or 5 lbs. not recommended due to slow freezing rate

    •Dry products

    •Containers may be filled to capacity


    •Leave ~10% headspace to allow for expansion during freezing
  95. Blanching
    —Most vegetables blanched prior to freezing

    —Improves color, flavor, and texture (largely due to enzyme inactivation)

    —Reduces microbial load

    —Provides better packing

    —Wilts leafy vegetables like spinach

    —Preserves nutrients (e.g., destruction of ascorbic acid oxidase preserves Vitamin C)

    —Removes objectionable odors and flavors
  96. Blanching - steps
    • 1. boiling water and ice bath
    • 2. plunge food into boiling water let cook (cooked yet crisp)
    • 3. plunge into ice bath halts cooking
    • 4.  keep in bath until cooled
  97. Drip:
  98. Pink or reddish liquid that comes from meat when it is thawed