Food Chem- Lecture 4

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Morgan.liberatore
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134467
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Food Chem- Lecture 4
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2012-02-12 13:32:26
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Food chem
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Food chem lecture 4
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  1. Which category do the bulk of our oils in North America fall into?
    Oleic-linoleic acid group
  2. What are some good examples of oleic-linoleic acids?
    Sunflower, Safflower, Olive, Cotton seed, Peanut and Corn oil
  3. How much of the total fatty acid composition do saturated fatty acids make up in the oleic-linoleic acid group?
    saturated fatty acids comprise of less than 20% of the total fatty acid coposition
  4. How does high unsaturation affect the oils in the oleic-linoleic acid group?
    High unsaturated makes them oils the predominant fatty acids are long chain
  5. Why is it important that only negligible quantities of linolenic are present in the oleic-linoleic acid group?
    The oils in this category do not suffer from reversion and are relatively stable
  6. What are oleic-linoleic acids often used for?
    These oils are widely used for food purposes; especially as salad oils and/or may be turned into plastic edible fats by partial hydrogenation to make shortenings
  7. What is the linolenic acid group?
    These oils contiain significant to high levels of linolenic acid (C18:3), usually in conjunction with oleic and linoleic acids
  8. Describe the stability of linolenic acid
    Particularly reactiva and is readily oxidized
  9. How do linolenic acid differ from oleic and linoleic acids?
    Overall, linolenic acids tend to contain very high levels of polyunsaturated fatty acids
  10. Why are most oils in the linolenic acid group categroized as industrial 'drying oils'?
    Because of their ability to polymerized into a hard filmn if applied as a thin layer on a surface (paint)
  11. What is the most common linolenic acid?
    Linseed oil
  12. What characteristic do all polyunsaturated oils have?
    Thing film polymerization capability is present in all polyunsaturated oils, however, those containing high levels of linolenate are much more reactive
  13. What are some other plant oils in the linolenic acid group?
    Soybean, castor, hempseed and perilla
  14. What was soybean oil originally used for?
    Imported to the US and originally used solely as an industrial drying oil due to its high linolenic acid content
  15. Why was soybean oil originally only used for industrial uses?
    Because soybean oil, which is generally unpalatable after conventional extraction would, even after processing and clean up, suffer from rapid off-flavor development, commonly termed reversion
  16. What is reversion?
    The relatively rapid transformation of an oil from a bland, odorless, tasteless oil obtained after cleanup and processing into one having a grassy, hay like and then fishy odor and flavor- making it hopeless for food use
  17. How was the problem of reversion solved?
    This problem was solved by hydrogenation, a process which converts a substantial portion of linolenic acid component of the triglycerode to oleic and linoleic acids by adding hydrogen across the double bonds- reducing the overall degree of unsaturation of the oil
  18. How did hydrogenation help the prevention of reversion?
    Hydrogenation stabilized the oil and also allowed plastic fats to be produced from this oil
  19. What is a side reaction associated with hydrogenation?
    The formation of trans fatty acids- trans fatty acids are now considered to contiute to arteriosclerosis
  20. What is flax seed oil an imporant source of?
    alpha-linolenic acid, an essential omega-3 fatty acid
  21. Why do omega-e capsules often taste bad if you even chew them?
    Because such oils are very unstable oxidatively
  22. Why are animal fats considered fats rather than oils?
    Because even though they are relatively unsaturated, it is due to the selective positional fatty acid distribution on the glycerol backbone
  23. Describe the positional distribution of saturation in animal fats
    The animal fat depot group has a higher ratio of di-saturated (G-S2U) and tri-saturated (G-S3) glycerides than that found in the oleic-linoleic acid group of oils
  24. How do high amounts of G-S3 affect the physical properties of the lipid?
    The presenceof relatively high amounts of G-S3 can strongly affect the physical characteristics of the lipid system and change it from an oil to a fat
  25. Describe the saturated-ness of fish oils
    Fish oils generally contain fairly low levels of saturated fatty aids and tend to be very high in long to very long chain poly-unsaturated fatty acids (C16-C22)
  26. What are fish oils a very good source of?
    Very rich source of long chain, essential OMEGA-3 fatty acids
  27. What are the most common omega-3s?
    • Eicosapentaneoic acid (EPA-C20:5)
    • Docosahexaenoic Acid (DHA-C22:6)
  28. Where are EPA and DHA found?
    Come from microalgae on which plankton and fish feed- can move up the food chain, but can also be produced from the source
  29. What are omega-3s a precursor for?
    Eicosanoids- involve in inflammation and immunity systems and are essential FAs
  30. Why are dish oils difficult to process?
    Pose particular processing and refining problems due to their very high degree ofunsaturation and these oils also suffer badly from reversion
  31. Why mush fish oils be stabilized with antioxidants?
    They are very susceptible to autoxidation after refining if not hydrogenated and/or stabilized with antioxidants
  32. How does europe use fish oils?
    Europe- processed fish oils are used extensively, especially for manufacturing margarine and shortening, but require hydrogenation, or blending with other oils andor interesterification
  33. What group does mustard (Rapseed) oils belong to?
    Erucic acid group
  34. What is the erucic acid group?
    When extracted, it is a mixture of triacylglycerols (dominant) as well as some essential oil which gives it its flavor/bite (usually removed from the refined oil)
  35. What was rapseed oil mostly used for in north america and why?
    In north america, rapseed was largely used as a marine motor oil due to its excellend lubricating properties and oxidative stability- attributed to its high erucic acid (C22:1) content
  36. How much erucic acid does conventional rapeseed oil contain?
    40-50%
  37. Why is rapeseed oil considered a health hazard?
    Considered a health hazard because of the high FFA content (40-50% erucic acid) - there is evidence that erucic acid infuses into the heart muscle of rats producing fatty deposits
  38. How did Canada deal with the high erucic acid content of rapeseed oil?
    In Canada, where rapeseed grows particularily well, rapeseed has been converted by plant breeding to a low erucic acid variety with properties similar to the oleic-linoleic acid oils (trade name Canola)
  39. What are high erucic oils used for?
    High erucic oils are coming back as biodegradable lubricants (chain saw oil, 2-cycle engine oils)

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