Food Sci-2

  1. How do microwaves compare to ionizing irradiation waves?
    Microwaves are much lower energy and longer wavelengths
  2. What is the frequency range of microwaves?
    20,000-400 MHz
  3. What was the first microwave?
    Amanda radar-range
  4. Why are we limited in wavelength for microwave use?
    Because the same range is used for communications and it would interfere
  5. What frequency do industrial microwaves commonly operate at?
    915 MHz
  6. What frequency do home microwaves operate at?
    2.5 GHz
  7. How do microwaves react with metals?
    They are reflected
  8. How do microwaves react with pastic and glass?
    They pass through
  9. What is 'loss factor'?
    Degree of absorption of microwaves
  10. What material has a high loss factor?
  11. What material has a low loss factor?
  12. Why are microwaves efficient sources of heat transfer?
    They pentrate and release their energy throughout the product- thus largely overcome slower process of heat conduction
  13. How do salts contribute to microwave heat exchange?
    Salts contribute by electrophoretic heating
  14. How are microwaves used to heat up water?
    Water molecules try to align with the wave which changes direction 915,000,000 (for 915 MHz) per second, this causes intermolecular friction resulting in the product heating up rapidly
  15. What foods is a lower frequency microwave used for?
    Conductive fluids
  16. What are the limitations of microwaves?
    Temperatures do not rise above 100°C for moisture containing foods
  17. What is suscepter packaging?
    Converts microwaves into inrared
  18. What foods is Ohmic heating beneficial for?
    Fluids containing particulates
  19. How does Ohmic heating work?
    • Product is placed between plates (electrodes) and exposed to an alternating current (50-60 Hz)
    • Electric current tries to pass through the product and the resistance encountered heats the product
  20. What do products require for Ohmic heating to be effective?
    A minimum and controlled amount of ionic content (salt) to partially conduct
  21. Why do foods need salt to conduct ohmic heating?
    Particulates containing salt heat more rapidly, tansfering their heat to the fluid- avoids center-point (cold point) lag
  22. What is the main benefit of Ohmic heating?
    Avoids excessive surface heating (burn-on) which reduces quality
  23. What is pulse electric field processing?
    • Pulses of 15,000-30,000 V/cm2
    • Kills vegetative bacteria
  24. What is PEF an alternative for?
    Low temperature alternative to heat pasteurization
  25. What is the benefit of PEF processing?
    Less effect on delicate flavor constituents
  26. How does PEF processing work?
    Strong electric pulses produced between two plates disrupt the porosity of cell memebranes (bacteria/tissue) with little heating
  27. Why is PEF processing not a complete process?
    • Enzymes are not destroyed
    • Need blanching
    • Refrigeration is required
  28. What is PEF processing used for?
    • Juice pasteurization
    • Enhance juice extraction from fruit tissue
  29. Food packaging alone cosumes over ___% of all packaging materils used
  30. Aside from preservation, what other roles does packaging serve?
    • Display
    • Advertise
    • Inform
  31. What does specialized packaging machinery do?
    • Fill
    • Form
    • Close
  32. What are some desirable features associated with an ideal package?
    • Non-toxic
    • Sanitary and Rugged
    • Moisture/Fat protection
    • Gas/Odor protection
    • Light protection
    • Resistance to impact
    • Transparency
    • Tamper resistance
    • Ease of opening
    • Low weight
    • Pouring feature
    • Re-sealing capabiity
    • Ease of disposal
    • Size/Shape/Weight
    • Appearance
    • Special Features
  33. Why is it important for packages to provide light protection?
    Reduce product autoxidation/color fading
  34. Why is it important for packaging to have low weight?
    Shipping costs
  35. How are containers/packages classified?
    • Primary
    • Secondary
    • Tertiary
  36. What is primary packagin?
    Comes into contact with food
  37. What is secondary packaging?
    Often provides for rigidity, printing, or grouping into larger units
  38. What is an alternative classification system for packaging?
  39. What is an example of rigid packaging?
    • Cans
    • Jars
  40. What is an example of semi-ridig packaging?
    • Squeeze bottle
    • Tetra brick
  41. What is an example of flexible packaging?
    • Retort pouch
    • Plastic bags
  42. What is hermetic packaging?
    A hermetic package, by definition, is impermeal to fases and vapors
  43. What is an example of a hermetic package?
    Cans, Bottles, Tetra brick
  44. What is the downside of many flexible packages?
    Many flexible packages are semi-permeable to gasses, susceptible to pinholes and their seals may be imperfect
  45. What are some common packaging materials?
    • Metal
    • Glass
    • Paper
    • Plastics
    • Plastic/Metal/Paper/Laminates combos
  46. What is the 'tin can' originally made of?
    Steel with a thin coating of tin to prevent rusting
  47. What are tin cans made of now?
    Base steel usually coated with chrome
  48. Why do some cans include speciaized internal coatings?
    For acid and other corrosive food products, such as pineapple
  49. What is the rate of manufacturing and sealing cans?
  50. What is the can's seal made up of?
    Five metal folds, sealed by epoxy
  51. Why are cans ribbed?
    So the can can survive the retort pressure changes
  52. What is the most popular material for 2 piece cans?
  53. Why is aluminum often used for cans?
    Light and resistant to atmospheric corrosion and malleable
  54. What do aluminum cans need to maintain their shape?
    Internal pressure (soft drinks/beer)
  55. What is the convenience of aluminum cans?
    Pull tab
  56. What is aluminum foil used for in pther types of packaging?
    Used as a laminate to provide gas/vapor barrier in other packaging materials such as the retort pouch
  57. Why is aluminum a very preferred material for all packaging?
    Economical to recycle
  58. What is an advantage of glass packaging?
    Chemically inert and transparent
  59. What are the disadvantages to glass packaging?
    Brittle and heavy
  60. How can glass breakage be reduced substantially?
    Adding coatings to glass
  61. How do you make glass?
    Combine sand, soda ash, and limestone and heat to 1500°C and blow mold
  62. What is the disadvantage of glass in retorts?
    Susceptible to mechanical and thermal shock
  63. What has brought glass back as a major packaging contender
  64. Why is paper often used for packaging?
    Cheap and versatile
  65. Why is paper packaging often waxed?
    To prevent loss of strength due to moisture ingression
  66. What is the most predominant form of pastic in the food industry?
    Wraps, films and packages
  67. What are the two types of plastic polymers that can be produced?
    Homo or Hetero
  68. How is plastic packagin formed?
    Can be melted and blown into containers and formed into films
  69. What are some typical films?
    • Cellophane
    • Nylon
    • Mylar
    • Polyethylene
  70. What is cellophane?
    regenerated cellulose
  71. What is nylon made of?
  72. What is mylar made of?
    Polyester resin
  73. What was the original saran made of?
    Vinylidene Chloride
  74. What are some very specific properties we can obtain with plastic films?
    • Moisture or gas barriers
    • Selective permeability's (water vapor, O2, CO2)
Card Set
Food Sci-2
Food Sci-2