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food chem 1 > 2 FAs and TGs > Flashcards

2 FAs and TGs Flashcards

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1
Q

what’s the characteristic that most predominantly determines a FAs role?

A

saturation

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2
Q

What kind of fatty acid is a monounsaturated FA?

A

omega-9

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3
Q

what are some sources of monounsaturated FAs?

A

olive oil, avocado, peanuts, almonds

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4
Q

what kind of fatty acids are polyunsaturated FAs?

A

omega 3 and omega 6

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5
Q

what are some sources of omega 3s?

A

fish/shellfish (eicosapentaenoic acid and docosahexaenoic acid)
- flax seed/soybean/walnut/rapeseed (alpha-linolenic acid

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6
Q

what is more reactive: a saturated or unsaturated FA?

A

unsaturated (double bond is a better source of electrons)

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7
Q

do FAs mostly have an even or odd number of carbons?

A

even

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8
Q

what odd number FAs are present in milk?

A

pentadecanoic and heptadecanoic (15 and 17)

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9
Q

what # carbon range is miscible with water?

A

C4-C8

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10
Q

what are the most common unsaturated FAs?

A

oleic, linoleic, linolenic

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11
Q

in the FA naming system, what do the ##s mean in ##:## (####)

A

No. carbons:degree of unsaturation (where the db is)

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12
Q

How would you name an 18-carbon FA with a cis double bond on the 9 position and a trans double bond on the 12 position? What’s its shorthand?

A

octadeca-cis-9-trans-12-dienoic acid; 18:2(9c,12t)

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13
Q

what conformation, cis or trans, are FAs most often found in nature?

A

cis

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14
Q

why do the presence of double bonds decrease a FA’s melting point?

A

creates kink in chain  leads to a more unstably packed lattice

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15
Q

what is the name of the process that converts cis forms of FAs to trans?

A

hydrogenation

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16
Q

what happens as a result of hydrogenation?

A

oils become plastic; metabolized similarly to saturated FAs

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17
Q

when the double bond in oleic acid is converted to trans, what’s the name of this new FA?

A

elaidic

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18
Q

which is more commonly found in nature? Conjugated or unconjugated bonds? Why?

A

unconjugated. Conjugated are more likely to undergo autooxidation

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19
Q

what is reversion?

A

associated with soybean/fish oils. It’s when there’s an appearance of objectionable flavor from less oxidation than what’s normally required. Results from a mixed bonding system which leads to an active methylene group.

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20
Q

what is the crystal lattice stabilized by?

A

hydrophobic interaction along acyl residues

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21
Q

a fatty acid’s ability to ____________ determines its melting point

A

pack

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22
Q

when is the only situation in which a cis double bond will increase the melting point?

A

when it’s on the terminus of a carbon chain

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23
Q

what assumption does the omega naming system make?

A

all double bonds are cis; double bonds are unconjugated

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24
Q

consider C10:2 ω3. How many carbons? How many double bonds? Where are the double bonds?

A

10, 2, starting from the CH3 end, on positions 3 and 6.

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25
Q

how many conjugated bonds does natural linoleic acid have? Where are they?

A

2 on the 6 and 9 positions from the ω end

26
Q

how many conjugated bonds does arachidonic acid have? Where are they?

A

4 on the 6, 9, 12, and 15 positions from the ω end

27
Q

ω3 FAs are what type of FA?

A

linolenic

28
Q

ω6 FAs are what type of FA?

A

linoleic

29
Q

ω9 FAs are what type of FA?

A

oleic

30
Q

give an example of a FA that belongs to the ω9 group

A

Erucic acid (mustard)

31
Q

give an example of a FA that belongs to the ω6 group

A

arachidonic acid (meat, liver, lard, lipids of chicken and eggs)

32
Q

give an example of a FA that belongs to the ω3 group

A

C20-22 FAs (fish lipids)

33
Q

which ω types are considered essential fatty acids?

A

ω3 (linolenic) and ω6 (linoleic)

34
Q

what’s so fancy about CONJUGATED linoLEIC acids (CLAs)?

A

they are attributed to having anti-carcinogenic effects

35
Q

what’s the most common CLA?

A

cis-9-trans-11-octadecanoic acid (rumenic acid)

36
Q

what are the names of the 2 PUFAs with trans double bonds that you have to know?

A

Elaidic, linoelaidic.

37
Q

where are the trans bonds located in elaidic and linoelaidic acids?

A

tr9, tr9 and tr12

38
Q

what isn’t commonly found in natural FAs?

A

branched hydrocarbons, hydroxy acids, cyclic FAs, and acetylenic FAs

39
Q

give an example of a FA with branched hydrocarbons

A

malvalic acid. Also found in microorganisms

40
Q

give an example of a FA containing a OH group on its chain

A

ricinoleic acid

41
Q

what makes hydroxy acid FAs potentially useful?

A

their very reactive OH side chain

42
Q

what are acetylenic FAs used for?

A

antifungals

43
Q

name some examples of simple TGs

A

tristearin, triolene

44
Q

name some examples of mixed glycerides

A

stearodilinolein, dipalmitolinolenin, palmitostearolinolein

45
Q

what are the 4 steps to analyzing the composition of TGs?

A

1) extract fats
2) saponify using NaOH
3) methylate the FAs with methanol –> fatty acid methyl esters (FAMEs) which are volatile then proceed to use GC
4) identify/quantify against known FAME standards

46
Q

what are common plant sources of fats?

A

seeds and fruits. Particularly soybean, rapeseed (canola), peanut, olive, coconut, palm, biproducts of corn and cottonseed. Nonedible: castor oil and linseed (flax) oil

47
Q

what’s the edible version of linseed oil called?

A

linola

48
Q

what are the non-edible oils often used for

A

what are the non-edible oils often used for

49
Q

what are some common animal sources for fat?

A

by-products of meat production from cattle, hogs and sheep; milk of ruminants; fish (esp sardines, herring, menhaden)

50
Q

what are the distinguishing features of the milkfat group?

A
  • comes from milk of ruminants (cow, goat, sheep, yak, water buffalo)
  • high levels of LONG chain SATURATED fatty acids.
  • substantial amount of short chain fatty acids (C12 and C4) responsible for potentially desirable rancid flavors
  • most unsaturated bits are in TRANS form due to bio-hydrogenation
    • High to low: oleic, palmitic, stearic, butyric & other short chains
51
Q

what are the distinguishing features of the lauric acid group?

A
  • “tropical oils”
  • high content of lauric acid (40-50%)
  • mostly saturated
  • oils at room temp due to high portion of C12
  • resistant to oxidative rancidity due to low degree of unsaturation (aka mostly saturated) so long shelf life
  • can be fractionally crystalized
52
Q

what are the distinguishing features of the oleic/linoleic acid group?

A
  • predominantly composed of 18:1 and 18:2
  • sat fats make up <20%
  • not much 18:3 therefore little reversion –> more shelf stable
  • can be partially hydrogenated to become more plastic
53
Q

what are the distinguishing features of the linolenic acid group?

A

predominantly composed of 18:3, usually in conjunction with oleic and linoleic groups; “drying oils” – they have the ability to polymerize into a hard film (like paint) when applied in a thin layer; ex) soybean, castor, linseed, hempseed, perilla oil
• Soybean was originally a drying oil but then got developed into an edible one
• Can undergo REVERSION – rapid transition of bland, tasteless oil shortly after processing

54
Q

what are some distinguishing features of the animal fat depot group?

A

lard from pigs/tallow from sheep & cows; higher melting points due to fatty acid distribution; 50-60% oleic and linoleic acid; as a higher ratio of desaturated (gs2u) and trisaturated (gs3) glycerides than oleic/linoleic group30-40% palmitic and stearic acid.

55
Q

what are distinguishing features of the marine oil group?

A

low sat fat, high long chain FAs; can be very unsaturated; very susceptible to autoxidation

56
Q

what are distinguishing features of the erucic acid group?

A

rapeseed/mustard oil; high 22:1 content; rapeseed has 40-50% erucic acid; can be converted to canola

57
Q

as chain length increases, melting point __________

A

increases

58
Q

as chain length increases, volatility __________

A

decreases

59
Q

as chain length increases, water solubility __________

A

decreases

60
Q

as degree of unsaturation increases, melting point __________

A

decreases

food chem 1 (12 decks)

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